Docente
Paula Homem-de-Mello
Publicações
2026
de Araujo, Karen Rafaela Gonçalves; de Paula Meirelles, Gabriela; Carneiro, Leonardo Martins; Godoi, Alexandre Barcia; Aith, Fernando Mussa Abujamra; da Costa, José Luiz; Homem-de-Mello, Paula; Yonamine, Mauricio
Exploring dual-use risks of large language models for new psychoactive substances: a severity-based vulnerability analysis Journal Article
Em: International Journal of Drug Policy, vol. 156, 2026, ISSN: 0955-3959.
@article{deAraujo2026,
title = {Exploring dual-use risks of large language models for new psychoactive substances: a severity-based vulnerability analysis},
author = {Karen Rafaela Gonçalves de Araujo and Gabriela de Paula Meirelles and Leonardo Martins Carneiro and Alexandre Barcia Godoi and Fernando Mussa Abujamra Aith and José Luiz da Costa and Paula Homem-de-Mello and Mauricio Yonamine},
doi = {10.1016/j.drugpo.2026.105467},
issn = {0955-3959},
year = {2026},
date = {2026-10-00},
urldate = {2026-10-00},
journal = {International Journal of Drug Policy},
volume = {156},
publisher = {Elsevier BV},
abstract = {Recent advances in large language models (LLMs) have profoundly transformed scientific research in chemistry, enabling literature mining, the prediction of physicochemical and biological properties, and even the generation of novel molecular structures. However, such tools also raise concerns regarding malicious use, particularly in the context of the clandestine synthesis of new psychoactive substances (NPSs). In this study, we evaluate simulated scenarios of interaction with LLM-based chatbots to explore potential vulnerabilities in the provision of information that could facilitate illicit synthesis. Inspired by recent methodologies that apply LLMs to chemistry, we designed conceptual experiments involving different types of queries, ranging from neutral consultations to explicit attempts to obtain hazardous instructions. Our findings indicate that, although the models often refuse to provide direct answers, risks remain associated with the release of indirect information, bibliographic references, and technical details that could be exploited indiscriminately. The discussion emphasizes ethical and regulatory implications, proposing the need for red teaming strategies, risk-oriented databases, and cross-sectoral cooperation to mitigate potential misuse. This study contributes to the emerging debate on digital security in chemical sciences and outlines future directions for the responsible use of artificial intelligence.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Recent advances in large language models (LLMs) have profoundly transformed scientific research in chemistry, enabling literature mining, the prediction of physicochemical and biological properties, and even the generation of novel molecular structures. However, such tools also raise concerns regarding malicious use, particularly in the context of the clandestine synthesis of new psychoactive substances (NPSs). In this study, we evaluate simulated scenarios of interaction with LLM-based chatbots to explore potential vulnerabilities in the provision of information that could facilitate illicit synthesis. Inspired by recent methodologies that apply LLMs to chemistry, we designed conceptual experiments involving different types of queries, ranging from neutral consultations to explicit attempts to obtain hazardous instructions. Our findings indicate that, although the models often refuse to provide direct answers, risks remain associated with the release of indirect information, bibliographic references, and technical details that could be exploited indiscriminately. The discussion emphasizes ethical and regulatory implications, proposing the need for red teaming strategies, risk-oriented databases, and cross-sectoral cooperation to mitigate potential misuse. This study contributes to the emerging debate on digital security in chemical sciences and outlines future directions for the responsible use of artificial intelligence.
de Castro, Alexandre A.; Silva, Henrique F.; Militani, Isabela A.; Mesquita, Antônio P. L.; da Cunha, Elaine F. F.; Homem-de-Mello, Paula; Ramalho, Teodorico C.
In silico studies into the therapeutic potential of organophosphorus compounds against Alzheimer's disease Journal Article
Em: Letters in Drug Design & Discovery, 2026, ISSN: 1570-1808.
@article{deCastro2026,
title = {In silico studies into the therapeutic potential of organophosphorus compounds against Alzheimer's disease},
author = {Alexandre A. de Castro and Henrique F. Silva and Isabela A. Militani and Antônio P.L. Mesquita and Elaine F.F. da Cunha and Paula Homem-de-Mello and Teodorico C. Ramalho},
doi = {10.1016/j.lddd.2026.100560},
issn = {1570-1808},
year = {2026},
date = {2026-09-17},
urldate = {2026-09-00},
journal = {Letters in Drug Design & Discovery},
publisher = {Elsevier BV},
abstract = {Background: Alzheimer’s disease (AD) is the most prevalent form of dementia in the elderly and is
characterized by a progressive decline in cognitive function. Therapeutic strategies for AD have
largely been guided by the cholinergic hypothesis, which has driven the investigation of acetylcholinesterase inhibitors, including trichlorfon, as potential therapeutic agents.
Objectives: This study aims to propose novel organophosphorus (OP) compounds as HssAChE
inhibitors, based on the cholinergic hypothesis.
Methods: A diverse array of OP compounds was systematically evaluated using advanced computational approaches, along with rigorous statistical analyses. The most promising candidates
were further investigated through drug-likeness assessments, binding interaction analyses, and
mechanistic simulations.
Results: In particular, inhibitors 12, 13, 20, and 28 emerged as promising candidates for the
treatment of AD. However, following a detailed safety analysis, inhibitor 12 was identified as the
least toxic inhibitor, exhibiting favorable interactions with the molecular target. Molecular dynamics simulations indicated that inhibitor 12 is more energetically stabilized in the HssAChE
active site than the reference compound trichlorfon. QM/MM calculations further revealed a
lower energy barrier for the HssAChE inhibition mechanism.
Conclusions: These findings may facilitate the development of more effective and safer therapeutic options for the treatment of AD derived from this class of compounds.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Background: Alzheimer’s disease (AD) is the most prevalent form of dementia in the elderly and is
characterized by a progressive decline in cognitive function. Therapeutic strategies for AD have
largely been guided by the cholinergic hypothesis, which has driven the investigation of acetylcholinesterase inhibitors, including trichlorfon, as potential therapeutic agents.
Objectives: This study aims to propose novel organophosphorus (OP) compounds as HssAChE
inhibitors, based on the cholinergic hypothesis.
Methods: A diverse array of OP compounds was systematically evaluated using advanced computational approaches, along with rigorous statistical analyses. The most promising candidates
were further investigated through drug-likeness assessments, binding interaction analyses, and
mechanistic simulations.
Results: In particular, inhibitors 12, 13, 20, and 28 emerged as promising candidates for the
treatment of AD. However, following a detailed safety analysis, inhibitor 12 was identified as the
least toxic inhibitor, exhibiting favorable interactions with the molecular target. Molecular dynamics simulations indicated that inhibitor 12 is more energetically stabilized in the HssAChE
active site than the reference compound trichlorfon. QM/MM calculations further revealed a
lower energy barrier for the HssAChE inhibition mechanism.
Conclusions: These findings may facilitate the development of more effective and safer therapeutic options for the treatment of AD derived from this class of compounds.
characterized by a progressive decline in cognitive function. Therapeutic strategies for AD have
largely been guided by the cholinergic hypothesis, which has driven the investigation of acetylcholinesterase inhibitors, including trichlorfon, as potential therapeutic agents.
Objectives: This study aims to propose novel organophosphorus (OP) compounds as HssAChE
inhibitors, based on the cholinergic hypothesis.
Methods: A diverse array of OP compounds was systematically evaluated using advanced computational approaches, along with rigorous statistical analyses. The most promising candidates
were further investigated through drug-likeness assessments, binding interaction analyses, and
mechanistic simulations.
Results: In particular, inhibitors 12, 13, 20, and 28 emerged as promising candidates for the
treatment of AD. However, following a detailed safety analysis, inhibitor 12 was identified as the
least toxic inhibitor, exhibiting favorable interactions with the molecular target. Molecular dynamics simulations indicated that inhibitor 12 is more energetically stabilized in the HssAChE
active site than the reference compound trichlorfon. QM/MM calculations further revealed a
lower energy barrier for the HssAChE inhibition mechanism.
Conclusions: These findings may facilitate the development of more effective and safer therapeutic options for the treatment of AD derived from this class of compounds.
Santin, Luiza R. R.; Cabello, Calvin Q.; Santos, Sandra C.; Bianchini, Daniela; Moreira, Leonardo M.; Pellosi, Diogo Silva; Machado, Antonio E. H.; Araújo, Diesley M. S.; Romani, Ana Paula; Bettanin, Fernanda; Neto, Maurício D. Coutinho; Homem-de-Mello, Paula; Oliveira, Hueder P. M.
Theoretical and experimental photophysics of the dye 1,9- dimethyl methylene blue: Effect of aggregation in complex solvent mixtures Journal Article
Em: Journal of Molecular Structure, vol. 1366, 2026, ISSN: 0022-2860.
@article{Santin2026,
title = {Theoretical and experimental photophysics of the dye 1,9- dimethyl methylene blue: Effect of aggregation in complex solvent mixtures},
author = {Luiza R. R. Santin and Calvin Q. Cabello and Sandra C. Santos and Daniela Bianchini and Leonardo M. Moreira and Diogo Silva Pellosi and Antonio E. H. Machado and Diesley M. S. Araújo and Ana Paula Romani and Fernanda Bettanin and Maurício D. Coutinho Neto and Paula Homem-de-Mello and Hueder P. M. Oliveira},
doi = {10.1016/j.molstruc.2026.146041},
issn = {0022-2860},
year = {2026},
date = {2026-08-05},
journal = {Journal of Molecular Structure},
volume = {1366},
publisher = {Elsevier BV},
abstract = {The present work is focused on physicochemical evaluations involving a phenothiazinium compound, a class of molecules widely investigated as prototypes of photosensitizers (PS) for use in Photodynamic Therapy (PDT). We have employed UV–Vis absorption, steady-state and time-resolved fluorescence spectroscopies, combined with DFT and TD-DFT simulations to understand the photophysical properties of dimethylmethylene blue (DMMB) under distinct environmental conditions. Several binary mixtures of solvents were evaluated (water-organic solvents). The results show that DMMB aggregation is strongly modulated by solvent polarity and hydrogen-bonding ability. Water-rich media favor the formation of face-to-face H-aggregates, leading to hypsochromic shifts in the absorption spectra, fluorescence quenching, and shorter excited-state lifetimes. Increasing the organic solvent fraction shifts the monomer–dimer equilibrium toward monomeric species, enhancing fluorescence quantum yields and radiative decay rates. In low-polarity solvents, higher-order aggregates are formed, giving rise to an additional blue-shifted absorption band around 500 nm. Theoretical results support a solvent-mediated aggregation mechanism and reveal the role of intramolecular charge-transfer character in the excited state. These findings provide molecular-level insight into the structure–property relationships governing the photophysics of phenothiazinium derivatives.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The present work is focused on physicochemical evaluations involving a phenothiazinium compound, a class of molecules widely investigated as prototypes of photosensitizers (PS) for use in Photodynamic Therapy (PDT). We have employed UV–Vis absorption, steady-state and time-resolved fluorescence spectroscopies, combined with DFT and TD-DFT simulations to understand the photophysical properties of dimethylmethylene blue (DMMB) under distinct environmental conditions. Several binary mixtures of solvents were evaluated (water-organic solvents). The results show that DMMB aggregation is strongly modulated by solvent polarity and hydrogen-bonding ability. Water-rich media favor the formation of face-to-face H-aggregates, leading to hypsochromic shifts in the absorption spectra, fluorescence quenching, and shorter excited-state lifetimes. Increasing the organic solvent fraction shifts the monomer–dimer equilibrium toward monomeric species, enhancing fluorescence quantum yields and radiative decay rates. In low-polarity solvents, higher-order aggregates are formed, giving rise to an additional blue-shifted absorption band around 500 nm. Theoretical results support a solvent-mediated aggregation mechanism and reveal the role of intramolecular charge-transfer character in the excited state. These findings provide molecular-level insight into the structure–property relationships governing the photophysics of phenothiazinium derivatives.
Neto, Antonio Morais; Valeriano, Maycom Cezar; Homem-de-Mello, Paula; da Silva, Bruno Guzzo; Mamián-López, Mónica Benicia
A shorter path to circumventing the low reproducibility of SERS spectra through variable screening and optimization methodologies Journal Article
Em: Microchim Acta, vol. 193, não 8, 2026, ISSN: 1436-5073.
@article{Neto2026,
title = {A shorter path to circumventing the low reproducibility of SERS spectra through variable screening and optimization methodologies},
author = {Antonio Morais Neto and Maycom Cezar Valeriano and Paula Homem-de-Mello and Bruno Guzzo da Silva and Mónica Benicia Mamián-López},
doi = {10.1007/s00604-026-08306-x},
issn = {1436-5073},
year = {2026},
date = {2026-07-28},
urldate = {2026-08-00},
journal = {Microchim Acta},
volume = {193},
number = {8},
publisher = {Springer Science and Business Media LLC},
abstract = {Currently, several SERS methodologies are focused on quantitative goals, and, as they move toward becoming a suitable analytical alternative, their main drawback remains the low reproducibility of SERS signals. As a result, strategies to circumvent this are highly desirable, but given the number of experimental variables that affect reproducibility, the task can sometimes be endless. Here, we selected a series of C5-substituted uracil derivatives (5-fluoro-, 5-chloro-, and 5-bromouracil) adsorbed on silver nanoparticles. These compounds are of analytical and pharmacological interest due to their role as biomarkers, pharmaceuticals, or environmental pollutants. They are expected to be found at very low levels in bioanalytical matrices; thus, to reach low limits of detection, they were paired with adenine, which has a well-known high affinity for silver nanoparticles. Considering the complexity of these pairs and the experimental variables that affect SERS reproducibility, a two-stage strategy was adopted to select the best experimental conditions and minimize the standard deviation (STD) of the signals from the three base pairs. This included a variable screening procedure followed by an optimization stage. After optimization, the STD values decreased by 100-, 300-, and 1000-fold for 5-fluorouracil, 5-bromo, and 5-chlorouracil, respectively. The validation experiments yielded STD values at the same order of magnitude as those achieved under the optimized conditions, indicating that our approach can be applied to improve signal reproducibility. In perspective, this strategy can be easily adapted to other SERS-based systems, especially for analytical purposes.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Currently, several SERS methodologies are focused on quantitative goals, and, as they move toward becoming a suitable analytical alternative, their main drawback remains the low reproducibility of SERS signals. As a result, strategies to circumvent this are highly desirable, but given the number of experimental variables that affect reproducibility, the task can sometimes be endless. Here, we selected a series of C5-substituted uracil derivatives (5-fluoro-, 5-chloro-, and 5-bromouracil) adsorbed on silver nanoparticles. These compounds are of analytical and pharmacological interest due to their role as biomarkers, pharmaceuticals, or environmental pollutants. They are expected to be found at very low levels in bioanalytical matrices; thus, to reach low limits of detection, they were paired with adenine, which has a well-known high affinity for silver nanoparticles. Considering the complexity of these pairs and the experimental variables that affect SERS reproducibility, a two-stage strategy was adopted to select the best experimental conditions and minimize the standard deviation (STD) of the signals from the three base pairs. This included a variable screening procedure followed by an optimization stage. After optimization, the STD values decreased by 100-, 300-, and 1000-fold for 5-fluorouracil, 5-bromo, and 5-chlorouracil, respectively. The validation experiments yielded STD values at the same order of magnitude as those achieved under the optimized conditions, indicating that our approach can be applied to improve signal reproducibility. In perspective, this strategy can be easily adapted to other SERS-based systems, especially for analytical purposes.
Melo, Diego Ulysses; Boaro, Andreia; Reis, Roberta Albino; Carneiro, Leonardo Martins; Homem-de-Mello, Paula; Bartoloni, Fernando Heering
Regioisomeric Control of Chemiexcitation Efficiency in Lophine Silylperoxides through Reaction-Path Topology and Excited-State Accessibility Journal Article
Em: ACS Org. Inorg. Au, 2026, ISSN: 2694-247X.
@article{Melo2026,
title = {Regioisomeric Control of Chemiexcitation Efficiency in Lophine Silylperoxides through Reaction-Path Topology and Excited-State Accessibility},
author = {Diego Ulysses Melo and Andreia Boaro and Roberta Albino Reis and Leonardo Martins Carneiro and Paula Homem-de-Mello and Fernando Heering Bartoloni},
doi = {10.1021/acsorginorgau.6c00037},
issn = {2694-247X},
year = {2026},
date = {2026-06-29},
urldate = {2026-06-29},
journal = {ACS Org. Inorg. Au},
publisher = {American Chemical Society (ACS)},
abstract = {This study investigates the chemiluminescence (CL) of silylperoxides derived from lophines and their associated high-energy intermediates (HEIs), specifically 1,2-dioxetanes. Three regioisomeric silylperoxides (D1–3), differing in the position of the –O– group, were synthesized, and their CL and kinetic behavior under fluoride-induced decomposition were examined. Notably, the ortho-substituted derivative (D1) exhibits a 100-fold and 10-fold increase in singlet excited-state formation quantum yield compared to its meta (D2) and para (D3) counterparts, respectively. Computational analysis using density functional theory (DFT) and time-dependent DFT (TD-DFT) indicates that chemiexcitation proceeds through a single-step asynchronous-concerted mechanism with pronounced biradical character along O–O bond cleavage. The differences in singlet quantum yields are rationalized by a combined effect of the extent of the biradical/near-degenerate region and the relative accessibility of excited-state surfaces along the reaction path. In particular, the enhanced efficiency of D1 arises from its prolonged residence in near-degenerate regions together with a more favorable energetic balance for singlet-state formation relative to triplet-state stabilization. These findings provide a mechanistic framework for understanding substituent effects in chemiexcitation and suggest that tuning reaction-path topology and excited-state energetics may guide the rational design of improved chemiluminescent systems.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
This study investigates the chemiluminescence (CL) of silylperoxides derived from lophines and their associated high-energy intermediates (HEIs), specifically 1,2-dioxetanes. Three regioisomeric silylperoxides (D1–3), differing in the position of the –O– group, were synthesized, and their CL and kinetic behavior under fluoride-induced decomposition were examined. Notably, the ortho-substituted derivative (D1) exhibits a 100-fold and 10-fold increase in singlet excited-state formation quantum yield compared to its meta (D2) and para (D3) counterparts, respectively. Computational analysis using density functional theory (DFT) and time-dependent DFT (TD-DFT) indicates that chemiexcitation proceeds through a single-step asynchronous-concerted mechanism with pronounced biradical character along O–O bond cleavage. The differences in singlet quantum yields are rationalized by a combined effect of the extent of the biradical/near-degenerate region and the relative accessibility of excited-state surfaces along the reaction path. In particular, the enhanced efficiency of D1 arises from its prolonged residence in near-degenerate regions together with a more favorable energetic balance for singlet-state formation relative to triplet-state stabilization. These findings provide a mechanistic framework for understanding substituent effects in chemiexcitation and suggest that tuning reaction-path topology and excited-state energetics may guide the rational design of improved chemiluminescent systems.
Toledo, Victor H.; Leão, Cedric R.; Homem-de-Mello, Paula; Nascimento, Otaciro R.; Nantes, Iseli L.
Long-Lived Charge Separation and Ionosolvatochromism of Methylene Blue Journal Article
Em: ACS Omega, 2026, ISSN: 2470-1343.
@article{Toledo2026,
title = {Long-Lived Charge Separation and Ionosolvatochromism of Methylene Blue},
author = {Victor H. Toledo and Cedric R. Leão and Paula Homem-de-Mello and Otaciro R. Nascimento and Iseli L. Nantes},
doi = {10.1021/acsomega.6c01448},
issn = {2470-1343},
year = {2026},
date = {2026-05-20},
urldate = {2026-05-20},
journal = {ACS Omega},
publisher = {American Chemical Society (ACS)},
abstract = {Methylene Blue (MB+) is a thiazine dye that has gained significant interest due to its diverse applications in health and technology. Here, two important findings regarding the formation of MB+-derived species are presented: photoinduced long-lived charge separation in organic solvents and the mechanism of the dye’s conversion to a red form. Previous studies have relied on ultrafast techniques─such as flash photolysis and transient adduct formation─to detect MB+’s excited states and radical intermediates. We now report on the production of three MB+-derived species formed after the exchange of the counterion Cl– to OH– in aprotic solvents, DMSO and toluene: MB2+•, MB•, and methylene red (MR+). The long-lived free radicals generated by charge separation and stabilized by π*–π* interactions were detected by the steady-state UV–visible spectroscopy and direct continuous-wave electron paramagnetic resonance (CW-EPR) spectroscopy. MR+ is an ionosolvatochromic species formed by trimers and tetramers of [MB+][OH–] in DMSO and toluene. Theoretical calculations supported the spectral assignments of radical cations and aggregates. These findings demonstrate a novel approach to stabilizing MB+ radical cations and aggregates, and to the ionosolvatochromism of MB+, thereby unlocking new avenues for its application in catalysis, synthetic chemistry, postlithium batteries, and biomedical technologies.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Methylene Blue (MB+) is a thiazine dye that has gained significant interest due to its diverse applications in health and technology. Here, two important findings regarding the formation of MB+-derived species are presented: photoinduced long-lived charge separation in organic solvents and the mechanism of the dye’s conversion to a red form. Previous studies have relied on ultrafast techniques─such as flash photolysis and transient adduct formation─to detect MB+’s excited states and radical intermediates. We now report on the production of three MB+-derived species formed after the exchange of the counterion Cl– to OH– in aprotic solvents, DMSO and toluene: MB2+•, MB•, and methylene red (MR+). The long-lived free radicals generated by charge separation and stabilized by π*–π* interactions were detected by the steady-state UV–visible spectroscopy and direct continuous-wave electron paramagnetic resonance (CW-EPR) spectroscopy. MR+ is an ionosolvatochromic species formed by trimers and tetramers of [MB+][OH–] in DMSO and toluene. Theoretical calculations supported the spectral assignments of radical cations and aggregates. These findings demonstrate a novel approach to stabilizing MB+ radical cations and aggregates, and to the ionosolvatochromism of MB+, thereby unlocking new avenues for its application in catalysis, synthetic chemistry, postlithium batteries, and biomedical technologies.
Andrade, Karine N.; Souza, Jhonathan Rosa; Homem-de-Mello, Paula; Fiorot, Rodolfo G.
Light-Assisted Akamptisomerization: Excited-State Bond-Angle Reflection (ESBAR) as a Molecular Photoswitching Element in B _2 OF _2 –Porphyrins Journal Article
Em: Inorg. Chem., vol. 65, não 13, pp. 7093–7097, 2026, ISSN: 1520-510X.
@article{deAndrade2026,
title = {Light-Assisted Akamptisomerization: Excited-State Bond-Angle Reflection (ESBAR) as a Molecular Photoswitching Element in B _2 OF _2 –Porphyrins},
author = {Karine N. Andrade and Jhonathan Rosa Souza and Paula Homem-de-Mello and Rodolfo G. Fiorot},
doi = {10.1021/acs.inorgchem.6c00108},
issn = {1520-510X},
year = {2026},
date = {2026-03-26},
urldate = {2026-04-06},
journal = {Inorg. Chem.},
volume = {65},
number = {13},
pages = {7093–7097},
publisher = {American Chemical Society (ACS)},
abstract = {Akamptisomerism arises from bond-angle reflection (BAR) at a B–O–B bridge in low-symmetry B2OF2 porphyrins and leads to isolable diastereisomers in the ground state. Herein, we present the first theoretical investigation of the excited-state bond-angle reflection (ESBAR). TD-DFT calculations show that the BAR activation barrier decreases from 21.3 kcal mol–1 (0.924 eV) in the ground-state (S0) to 15.3 kcal mol–1 (0.663 eV) in the triplet excited-state (T1), rendering the process fluxional upon excitation. The feasibility of singlet–triplet intersystem crossing is supported by near-isoenergetic singlet and triplet states and enhanced spin–orbit coupling. These results provide substantial evidence that akamptisomerism could be facilitated in the excited state, highlighting ESBAR as a potential photoswitching mechanism in porphyrinoid systems.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Akamptisomerism arises from bond-angle reflection (BAR) at a B–O–B bridge in low-symmetry B2OF2 porphyrins and leads to isolable diastereisomers in the ground state. Herein, we present the first theoretical investigation of the excited-state bond-angle reflection (ESBAR). TD-DFT calculations show that the BAR activation barrier decreases from 21.3 kcal mol–1 (0.924 eV) in the ground-state (S0) to 15.3 kcal mol–1 (0.663 eV) in the triplet excited-state (T1), rendering the process fluxional upon excitation. The feasibility of singlet–triplet intersystem crossing is supported by near-isoenergetic singlet and triplet states and enhanced spin–orbit coupling. These results provide substantial evidence that akamptisomerism could be facilitated in the excited state, highlighting ESBAR as a potential photoswitching mechanism in porphyrinoid systems.
Amorim, Guilherme Gustavo Silva; Homem-de-Mello, Paula; Custodio, Rogério
TD-DFT Evaluation of Electronic Spectra of Coumarin and Anthraquinone Dyes: Effects of Functionals, Basis Sets, and Solvation Conditions Journal Article
Em: ACS Omega, 2026, ISSN: 2470-1343.
@article{Amorim2026,
title = {TD-DFT Evaluation of Electronic Spectra of Coumarin and Anthraquinone Dyes: Effects of Functionals, Basis Sets, and Solvation Conditions},
author = {Guilherme Gustavo Silva Amorim and Paula Homem-de-Mello and Rogério Custodio},
doi = {10.1021/acsomega.5c10203},
issn = {2470-1343},
year = {2026},
date = {2026-01-17},
urldate = {2026-01-17},
journal = {ACS Omega},
publisher = {American Chemical Society (ACS)},
abstract = {The electronic absorption spectra of 20 organic dyes (7 coumarins, 10 anthraquinones, and 3 other similar molecules) were investigated using TD-DFT with BLYP, B3LYP, and B3PW91 functionals and four basis sets: 6-31++G(d,p), 6-311++G(2df,p), aug-cc-pVDZ, and aug-cc-pVTZ. Gas-phase, implicit, and hybrid solvation models were tested. The hybrid model, guided by electrostatic potential maps, yielded the lowest mean absolute errors with respect to experimental absorption maxima, underscoring the role of specific electrostatic solute–solvent interactions. Overall, the solvent effects were most pronounced with B3LYP and B3PW91. Replacing the LYP correlation functional with PW91 led to shifts of up to 6 nm, while modifying the exchange term from B to B3 caused deviations of at least 33 nm. Basis set performance was consistent across molecules, showing approximately linear trends. Within this protocol, electrostatic-potential-guided microsolvation provides an efficient way to capture key solute–solvent interactions without resorting to more demanding QM/MM approaches.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The electronic absorption spectra of 20 organic dyes (7 coumarins, 10 anthraquinones, and 3 other similar molecules) were investigated using TD-DFT with BLYP, B3LYP, and B3PW91 functionals and four basis sets: 6-31++G(d,p), 6-311++G(2df,p), aug-cc-pVDZ, and aug-cc-pVTZ. Gas-phase, implicit, and hybrid solvation models were tested. The hybrid model, guided by electrostatic potential maps, yielded the lowest mean absolute errors with respect to experimental absorption maxima, underscoring the role of specific electrostatic solute–solvent interactions. Overall, the solvent effects were most pronounced with B3LYP and B3PW91. Replacing the LYP correlation functional with PW91 led to shifts of up to 6 nm, while modifying the exchange term from B to B3 caused deviations of at least 33 nm. Basis set performance was consistent across molecules, showing approximately linear trends. Within this protocol, electrostatic-potential-guided microsolvation provides an efficient way to capture key solute–solvent interactions without resorting to more demanding QM/MM approaches.
2025
a Paula Homem-de-Mello, * Débora A. C. Amoroso
Mulheres na Mecânica Quântica: A Força Feminina em Superposição com a Ciência Apresentação
06.12.2025.
@misc{https://rvq.sbq.org.br/pdf/CMQ2025-5063,
title = {Mulheres na Mecânica Quântica: A Força Feminina em Superposição com a Ciência},
author = {* Débora A. C. Amoroso a Paula Homem-de-Mello},
year = {2025},
date = {2025-12-06},
abstract = {In recognition of the Year of Quantum Science and Technology, this article provides a historical and
analytical overview of 18 pioneering Brazilian women scientists whose contributions have shaped the
field of quantum mechanics. Despite systemic barriers and limited visibility in mainstream scientific
discourse, these researchers played a fundamental role in advancing quantum theory and its applications.
By documenting their achievements and contextualizing their work within Brazil’s scientific landscape,
the article aims to emphasize the importance of gender diversity in STEM and to inspire young scientists
— particularly women — to pursue careers in physics and quantum research. This study not only honors
their legacy but also reinforces the transformative potential of inclusive science in building a more
innovative and equitable future.
Keywords: Quantum mechanics; women in STEM; brazilian scientists.},
keywords = {},
pubstate = {published},
tppubtype = {presentation}
}
In recognition of the Year of Quantum Science and Technology, this article provides a historical and
analytical overview of 18 pioneering Brazilian women scientists whose contributions have shaped the
field of quantum mechanics. Despite systemic barriers and limited visibility in mainstream scientific
discourse, these researchers played a fundamental role in advancing quantum theory and its applications.
By documenting their achievements and contextualizing their work within Brazil’s scientific landscape,
the article aims to emphasize the importance of gender diversity in STEM and to inspire young scientists
— particularly women — to pursue careers in physics and quantum research. This study not only honors
their legacy but also reinforces the transformative potential of inclusive science in building a more
innovative and equitable future.
Keywords: Quantum mechanics; women in STEM; brazilian scientists.
analytical overview of 18 pioneering Brazilian women scientists whose contributions have shaped the
field of quantum mechanics. Despite systemic barriers and limited visibility in mainstream scientific
discourse, these researchers played a fundamental role in advancing quantum theory and its applications.
By documenting their achievements and contextualizing their work within Brazil’s scientific landscape,
the article aims to emphasize the importance of gender diversity in STEM and to inspire young scientists
— particularly women — to pursue careers in physics and quantum research. This study not only honors
their legacy but also reinforces the transformative potential of inclusive science in building a more
innovative and equitable future.
Keywords: Quantum mechanics; women in STEM; brazilian scientists.
Carneiro, Leonardo Martins; Araújo, Karen Rafaela Gonçalves; Melo, Diego Ulysses; Bartoloni, Fernando Heering; Soares, Alexandre Learth; Yonamine, Mauricio; Homem-de-Mello, Paula
Computational-Assisted Development of Molecularly Imprinted Polymers for Synthetic Cannabinoid Recognition Journal Article
Em: ACS Omega, 2025, ISSN: 2470-1343.
@article{Carneiro2025b,
title = {Computational-Assisted Development of Molecularly Imprinted Polymers for Synthetic Cannabinoid Recognition},
author = {Leonardo Martins Carneiro and Karen Rafaela Gonçalves Araújo and Diego Ulysses Melo and Fernando Heering Bartoloni and Alexandre Learth Soares and Mauricio Yonamine and Paula Homem-de-Mello},
doi = {10.1021/acsomega.5c03148},
issn = {2470-1343},
year = {2025},
date = {2025-07-24},
urldate = {2025-07-24},
journal = {ACS Omega},
publisher = {American Chemical Society (ACS)},
abstract = {Synthetic cannabinoids (SCs), a prominent class of new psychoactive substances, pose growing challenges to public health due to their severe toxic effects and widespread global presence. In this study, we employed computational methods to develop molecularly imprinted polymers (MIPs) for the selective recognition of seven SCs, chosen based on seizure reports from the Narcotics Examination Unit of the Scientific Police of the State of São Paulo. Density functional theory and extended tight binding for geometry, frequency, and noncovalent model 2 (GFN2-xTB) calculations were used to optimize the molecular geometries and predict ideal monomer–solvent combinations for MIP synthesis. We assessed six solvents─acetone, acetonitrile, dichloromethane, chloroform, diethyl ether, and dimethyl sulfoxide─based on their solvation energy, identifying suitable candidates for the polymerization step. Hydrogen bonding interaction sites were mapped, guiding the selection of functional monomers such as acrylic acid (AA), 4-vinylbenzoic acid (BA), 2-(trifluoromethyl)acrylic acid (TFAA), and methacrylic acid. Our findings suggest that TFAA and BA offer the most stable complexation with SCs, influenced by their acidity and aromatic interactions. These computational predictions pave the way for resource-efficient experimental validation and enhance the development of MIPs as tools for the extraction of SCs in complex matrices, contributing to efforts to combat the global SC epidemic.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Synthetic cannabinoids (SCs), a prominent class of new psychoactive substances, pose growing challenges to public health due to their severe toxic effects and widespread global presence. In this study, we employed computational methods to develop molecularly imprinted polymers (MIPs) for the selective recognition of seven SCs, chosen based on seizure reports from the Narcotics Examination Unit of the Scientific Police of the State of São Paulo. Density functional theory and extended tight binding for geometry, frequency, and noncovalent model 2 (GFN2-xTB) calculations were used to optimize the molecular geometries and predict ideal monomer–solvent combinations for MIP synthesis. We assessed six solvents─acetone, acetonitrile, dichloromethane, chloroform, diethyl ether, and dimethyl sulfoxide─based on their solvation energy, identifying suitable candidates for the polymerization step. Hydrogen bonding interaction sites were mapped, guiding the selection of functional monomers such as acrylic acid (AA), 4-vinylbenzoic acid (BA), 2-(trifluoromethyl)acrylic acid (TFAA), and methacrylic acid. Our findings suggest that TFAA and BA offer the most stable complexation with SCs, influenced by their acidity and aromatic interactions. These computational predictions pave the way for resource-efficient experimental validation and enhance the development of MIPs as tools for the extraction of SCs in complex matrices, contributing to efforts to combat the global SC epidemic.
Melo, Diego Ulysses; Carneiro, Leonardo Martins; Coutinho-Neto, Mauricio Domingues; Homem-de-Mello, Paula; Bartoloni, Fernando Heering
Developing a Machine Learning Model for Hydrogen Bond Acceptance Based on Natural Bond Orbital Descriptors Journal Article
Em: J. Org. Chem., 2025, ISSN: 1520-6904.
@article{Melo2025,
title = {Developing a Machine Learning Model for Hydrogen Bond Acceptance Based on Natural Bond Orbital Descriptors},
author = {Diego Ulysses Melo and Leonardo Martins Carneiro and Mauricio Domingues Coutinho-Neto and Paula Homem-de-Mello and Fernando Heering Bartoloni},
doi = {10.1021/acs.joc.5c00724},
issn = {1520-6904},
year = {2025},
date = {2025-07-06},
urldate = {2025-07-06},
journal = {J. Org. Chem.},
publisher = {American Chemical Society (ACS)},
abstract = {This study employs machine learning (ML) to assess the predictive power of electronic descriptors derived from natural bond orbital (NBO) analysis for hydrogen bond acceptance. Using a data set of 979 hydrogen bond complexes, each formed by a hydrogen bond acceptor and 4-fluorophenol as the donor, we optimized geometries via GFN2-xTB, followed by DFT single-point calculations. From these, NBO analysis was used to extract intramolecular donor–acceptor interactions, particularly the orbital stabilization energies (E(2)), which reflect electron delocalization and relate to canonical resonance structures. The E(2) values served as features to train seven ML models, based on different techniques: KNN, Decision Tree, SVM, RF, MLP, XGBoost, and CatBoost. To our knowledge, this is the first work that uses E(2) as a standalone ML descriptor for hydrogen bond acceptance. Even with a small set of descriptors, we achieved high predictive performance, with errors below 0.4 kcal mol–1, surpassing previous studies that used heterogeneous descriptors, including quantum-chemical data. Our results highlight the utility of NBO-based features in building accurate, physically meaningful, and generalizable ML models for pKBHX prediction.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
This study employs machine learning (ML) to assess the predictive power of electronic descriptors derived from natural bond orbital (NBO) analysis for hydrogen bond acceptance. Using a data set of 979 hydrogen bond complexes, each formed by a hydrogen bond acceptor and 4-fluorophenol as the donor, we optimized geometries via GFN2-xTB, followed by DFT single-point calculations. From these, NBO analysis was used to extract intramolecular donor–acceptor interactions, particularly the orbital stabilization energies (E(2)), which reflect electron delocalization and relate to canonical resonance structures. The E(2) values served as features to train seven ML models, based on different techniques: KNN, Decision Tree, SVM, RF, MLP, XGBoost, and CatBoost. To our knowledge, this is the first work that uses E(2) as a standalone ML descriptor for hydrogen bond acceptance. Even with a small set of descriptors, we achieved high predictive performance, with errors below 0.4 kcal mol–1, surpassing previous studies that used heterogeneous descriptors, including quantum-chemical data. Our results highlight the utility of NBO-based features in building accurate, physically meaningful, and generalizable ML models for pKBHX prediction.
Carneiro, Leonardo Martins; Melo, Diego Ulysses; Cabello, Calvin Quessada; Homem‐de‐Mello, Paula; Ferreira, Fabio Furlan; Bartoloni, Fernando Heering
Em: Photochem & Photobiology, 2025, ISSN: 1751-1097.
@article{Carneiro2025,
title = {Triplet states nurture the long‐lived emission at room temperature of a chlorine‐containing tetraphenylimidazole derivative when aggregation occurs in water/acetonitrile mixtures},
author = {Leonardo Martins Carneiro and Diego Ulysses Melo and Calvin Quessada Cabello and Paula Homem‐de‐Mello and Fabio Furlan Ferreira and Fernando Heering Bartoloni},
doi = {10.1111/php.14096},
issn = {1751-1097},
year = {2025},
date = {2025-04-01},
urldate = {2025-04-01},
journal = {Photochem & Photobiology},
publisher = {Wiley},
abstract = {In recent years, there have been numerous reports on the synthesis and applications of 1,2,4,5-tetraphenylimidazole (TEPI) derivatives, particularly due to the photophysical properties of such systems. However, the long-lived emission behavior of TEPIs has not been studied, with research largely limited to attempts at 77 K. In this study, the compound 1-(4-chlorophenyl)-2,4,5-triphenyl-1H-imidazole (TEPI-Cl) was prepared and characterized using experimental techniques (i.e., absorption spectra, steady-state, and long-lived emission), as well as computationally, using a combination of Extended Tight Binding (xTB), Density Functional Theory (DFT), and Time-Dependent (TD-DFT) methods. TEPI-Cl exhibited a low solvatochromic effect, both in absorption and steady-state emission in organic solvents, which is typical of a locally excited transition; this was confirmed by the performed calculations. However, in its aggregated state (observed in water/acetonitrile mixtures with >80% of water, in volume), the compound displayed the emergence of a new band in the absorption spectrum, as well as aggregate-induced enhanced emission in the steady-state emission analysis. The long-lived emission spectrum of TEPI-Cl recorded at room temperature shows two signals (at 380 and 540 nm) and the presence of benzil enables the generation of triplet excited states of the latter, likely through an energy transfer process. The sensitivity of these signals to the presence of oxygen suggested that the related excited states are of a triplet nature; moreover, the calculated electronic transitions for the optimized structures of the T1 and T2 states are comparable to the experimentally observed long-lived emission wavelengths. This newly observed behavior of TEPI-Cl comes as a novel photophysical property added to this class of molecules, demonstrating its significant potential for further applications in complex matrices.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
In recent years, there have been numerous reports on the synthesis and applications of 1,2,4,5-tetraphenylimidazole (TEPI) derivatives, particularly due to the photophysical properties of such systems. However, the long-lived emission behavior of TEPIs has not been studied, with research largely limited to attempts at 77 K. In this study, the compound 1-(4-chlorophenyl)-2,4,5-triphenyl-1H-imidazole (TEPI-Cl) was prepared and characterized using experimental techniques (i.e., absorption spectra, steady-state, and long-lived emission), as well as computationally, using a combination of Extended Tight Binding (xTB), Density Functional Theory (DFT), and Time-Dependent (TD-DFT) methods. TEPI-Cl exhibited a low solvatochromic effect, both in absorption and steady-state emission in organic solvents, which is typical of a locally excited transition; this was confirmed by the performed calculations. However, in its aggregated state (observed in water/acetonitrile mixtures with >80% of water, in volume), the compound displayed the emergence of a new band in the absorption spectrum, as well as aggregate-induced enhanced emission in the steady-state emission analysis. The long-lived emission spectrum of TEPI-Cl recorded at room temperature shows two signals (at 380 and 540 nm) and the presence of benzil enables the generation of triplet excited states of the latter, likely through an energy transfer process. The sensitivity of these signals to the presence of oxygen suggested that the related excited states are of a triplet nature; moreover, the calculated electronic transitions for the optimized structures of the T1 and T2 states are comparable to the experimentally observed long-lived emission wavelengths. This newly observed behavior of TEPI-Cl comes as a novel photophysical property added to this class of molecules, demonstrating its significant potential for further applications in complex matrices.
Neto, Antonio M.; Valeriano, Maycom C.; Temperini, Marcia L. A.; Homem-de-Mello, Paula; Mamián-López, Mónica B.
Improving 5-halouracils SERS detection driven by Watson & Crick pairing recognition. A spectroscopic & DFT study Journal Article
Em: Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, vol. 337, 2025, ISSN: 1386-1425.
@article{Neto2025,
title = {Improving 5-halouracils SERS detection driven by Watson & Crick pairing recognition. A spectroscopic & DFT study},
author = {Antonio M. Neto and Maycom C. Valeriano and Marcia L. A. Temperini and Paula Homem-de-Mello and Mónica B. Mamián-López},
doi = {10.1016/j.saa.2025.126091},
issn = {1386-1425},
year = {2025},
date = {2025-03-22},
journal = {Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy},
volume = {337},
publisher = {Elsevier BV},
abstract = {The halogenated C5-substituted uracil derivatives (5-fluor-, 5-chloro, and 5-bromouracil) have drawn attention recently due to their pharmacological uses, properties, and importance as biomarkers and water pollutants. From an analytical point of view, these species are expected to be at very low levels in biological and environmental samples, and the development of methodologies for their determination is a central goal in research. The Raman technique and one of its special effects, Surface-Enhanced Raman Scattering (SERS), is a very suitable approach for detecting and quantifying these compounds. In practice, enhancing Raman scattering requires a nanostructured noble metal surface with the species of interest attached to it. Still, to maximize the effect, a deeper comprehension of the nature of the analyte-metal surface interaction is desirable. The structural information SERS spectra provide can be complemented by theoretical approaches, such as the Density Functional Theory (DFT) calculations. This work studied three 5-halouracils attached to silver nanoparticles (AgNPs) from experimental and theoretical perspectives. The observed patterns in the spectroscopic behavior showed a trend related to the electronegativity at the halogenated moieties, suggesting their direct influence in enhancing Cdouble bondC and Cdouble bondO stretching modes. Then, the formation of base pairs with adenine through hydrogen bonding was studied as a strategy to improve the detectability through SERS, supported by the well-known high affinity of adenine towards metal nanoparticles. We show that adenine favors the orientation of the 5-halouracils, reaching an additional signal enhancement that is very useful for analytical purposes, as demonstrated for 5-FU, reaching a limit of detection (LOD) of 2.36 nmol L−1. Wavenumber shifts and intensification of Nsingle bondH modes observed in the SERS spectra, along with DFT calculations, strongly suggest that forming hydrogen bonding (Nsingle bondH—-N) upon the interaction of the base pairs with an Ag20 cluster is key for improving the halouracils LOD through SERS.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The halogenated C5-substituted uracil derivatives (5-fluor-, 5-chloro, and 5-bromouracil) have drawn attention recently due to their pharmacological uses, properties, and importance as biomarkers and water pollutants. From an analytical point of view, these species are expected to be at very low levels in biological and environmental samples, and the development of methodologies for their determination is a central goal in research. The Raman technique and one of its special effects, Surface-Enhanced Raman Scattering (SERS), is a very suitable approach for detecting and quantifying these compounds. In practice, enhancing Raman scattering requires a nanostructured noble metal surface with the species of interest attached to it. Still, to maximize the effect, a deeper comprehension of the nature of the analyte-metal surface interaction is desirable. The structural information SERS spectra provide can be complemented by theoretical approaches, such as the Density Functional Theory (DFT) calculations. This work studied three 5-halouracils attached to silver nanoparticles (AgNPs) from experimental and theoretical perspectives. The observed patterns in the spectroscopic behavior showed a trend related to the electronegativity at the halogenated moieties, suggesting their direct influence in enhancing Cdouble bondC and Cdouble bondO stretching modes. Then, the formation of base pairs with adenine through hydrogen bonding was studied as a strategy to improve the detectability through SERS, supported by the well-known high affinity of adenine towards metal nanoparticles. We show that adenine favors the orientation of the 5-halouracils, reaching an additional signal enhancement that is very useful for analytical purposes, as demonstrated for 5-FU, reaching a limit of detection (LOD) of 2.36 nmol L−1. Wavenumber shifts and intensification of Nsingle bondH modes observed in the SERS spectra, along with DFT calculations, strongly suggest that forming hydrogen bonding (Nsingle bondH—-N) upon the interaction of the base pairs with an Ag20 cluster is key for improving the halouracils LOD through SERS.
2024
Vassiliades, Sandra V.; Argüello, Karina A. B.; Castro, Carlos E.; Silva, Clovis A.; Gonzalez, Ana Clara; Homem-de-Mello, Paula; Nantes, Iseli Lourenço; Aguilar, Andrea M.; Barbosa-Reis, Gustavo; Oliveira-Silva, Diogo; Giuntini, Francesca; Alves, Wendel A.
Synthesis, photophysical properties, and photocytotoxic effects of porphyrin-diphenylalanine conjugates on HeLa cells Journal Article
Em: Journal of Molecular Structure, vol. 1322, 2024, ISSN: 0022-2860.
@article{Vassiliades2025,
title = {Synthesis, photophysical properties, and photocytotoxic effects of porphyrin-diphenylalanine conjugates on HeLa cells},
author = {Sandra V. Vassiliades and Karina A. B. Argüello and Carlos E. Castro and Clovis A. Silva and Ana Clara Gonzalez and Paula Homem-de-Mello and Iseli Lourenço Nantes and Andrea M. Aguilar and Gustavo Barbosa-Reis and Diogo Oliveira-Silva and Francesca Giuntini and Wendel A. Alves},
doi = {10.1016/j.molstruc.2024.140545},
issn = {0022-2860},
year = {2024},
date = {2024-10-30},
journal = {Journal of Molecular Structure},
volume = {1322},
publisher = {Elsevier BV},
abstract = {Photodynamic therapy (PDT) triggers selective cell death through intensive oxidative stress induced by the generation of reactive species by a photosensitizer (PS) excited by light. In this work, we report the synthesis of four novel porphyrins conjugated to the self-assembling dipeptide L,L-diphenylalanine (FF), effectively inhibiting cervical tumor cell growth. The PS were prepared using the classical A3B strategy, with functionalized and non-functionalized porphyrins obtained in moderate yields over 3 to 4 steps. Absorption and fluorescence studies indicate that the FF attached to the porphyrin ring influences their aggregation at micromolar concentrations. The compounds were efficiently internalized by HeLa cells after 4 h of incubation. Cytotoxicity tests performed in the 1.25–5.0 µmol L−1 range showed that cell viability was reduced to 70 % after irradiation (650 nm). A correlation between cell permeation and the cell death mechanism promoted by the porphyrin was observed.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Photodynamic therapy (PDT) triggers selective cell death through intensive oxidative stress induced by the generation of reactive species by a photosensitizer (PS) excited by light. In this work, we report the synthesis of four novel porphyrins conjugated to the self-assembling dipeptide L,L-diphenylalanine (FF), effectively inhibiting cervical tumor cell growth. The PS were prepared using the classical A3B strategy, with functionalized and non-functionalized porphyrins obtained in moderate yields over 3 to 4 steps. Absorption and fluorescence studies indicate that the FF attached to the porphyrin ring influences their aggregation at micromolar concentrations. The compounds were efficiently internalized by HeLa cells after 4 h of incubation. Cytotoxicity tests performed in the 1.25–5.0 µmol L−1 range showed that cell viability was reduced to 70 % after irradiation (650 nm). A correlation between cell permeation and the cell death mechanism promoted by the porphyrin was observed.
Homem-de-Mello, Paula; Souza, Ana Clara Gonzalez; Melo, Diêgo U.; Mol, Gabriel S.; Souza, Jhonathan R. De; Carneiro, Leonardo M.; Nobrega, Maíra G.; Zanotto, Mateus; Corrêa, Raissa Lohanna G. Q.; Oliveira, Hueder P. M.; Bartoloni, Fernando H.; Aoto, Yuri A.; Coutinho-Neto, Maurício Domingues; Orestes, Ednilsom
DESIGN BIOINSPIRADO DE CORANTES Journal Article
Em: Quim. Nova, 2024, ISSN: 1678-7064.
@article{Homem-de-Mello2025,
title = {DESIGN BIOINSPIRADO DE CORANTES},
author = {Paula Homem-de-Mello and Ana Clara Gonzalez Souza and Diêgo U. Melo and Gabriel S. Mol and Jhonathan R. De Souza and Leonardo M. Carneiro and Maíra G. Nobrega and Mateus Zanotto and Raissa Lohanna G. Q. Corrêa and Hueder P. M. Oliveira and Fernando H. Bartoloni and Yuri A. Aoto and Maurício Domingues Coutinho-Neto and Ednilsom Orestes},
url = {https://www.scielo.br/j/qn/a/RCr5ZtRt4bVGwZhp5nxGSjP/},
doi = {10.21577/0100-4042.20250047},
issn = {1678-7064},
year = {2024},
date = {2024-09-09},
journal = {Quim. Nova},
publisher = {Sociedade Brasileira de Quimica (SBQ)},
abstract = {The history of the discovery, use, and development of dyes is closely linked to the history of humanity itself. Among the first records of human civilization are cave paintings made from, e.g., fruits, plants, minerals, and insects. Over the centuries, using different techniques, colors have been given to all types of materials and products, from clothing to food. The chemicals responsible for colors are dyes - a vast collection of molecules of the most varied compositions, but which have in common the absorption of light within the visible window of the electromagnetic spectrum. This article aims not only to review the properties of some classes of natural dyes, their origins, and their applications but also to describe the various computational chemistry methods involved in designing new bio-inspired molecules.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The history of the discovery, use, and development of dyes is closely linked to the history of humanity itself. Among the first records of human civilization are cave paintings made from, e.g., fruits, plants, minerals, and insects. Over the centuries, using different techniques, colors have been given to all types of materials and products, from clothing to food. The chemicals responsible for colors are dyes - a vast collection of molecules of the most varied compositions, but which have in common the absorption of light within the visible window of the electromagnetic spectrum. This article aims not only to review the properties of some classes of natural dyes, their origins, and their applications but also to describe the various computational chemistry methods involved in designing new bio-inspired molecules.
Maringolo, Vivian; Carvalho, Alexandre Z.; Homem-de-Mello, Paula; Zanotto, Mateus; Martins, Fernanda C. O. L.; Melchert, Wanessa R.; Rocha, Diogo L.
Spectrophotometric determination of bisphenol A in beverages using multi-dispersion calibration. Journal Article
Em: Food Control, 2024, ISSN: 0956-7135.
@article{Maringolo2024,
title = {Spectrophotometric determination of bisphenol A in beverages using multi-dispersion calibration.},
author = {Vivian Maringolo and Alexandre Z. Carvalho and Paula Homem-de-Mello and Mateus Zanotto and Fernanda C. O. L. Martins and Wanessa R. Melchert and Diogo L. Rocha},
url = {https://www.sciencedirect.com/science/article/pii/S0956713524005681},
doi = {10.1016/j.foodcont.2024.110851},
issn = {0956-7135},
year = {2024},
date = {2024-09-01},
journal = {Food Control},
publisher = {Elsevier BV},
abstract = {Bisphenol A (BPA) is an endocrine disruptor that may be present in plastics and coatings of food and beverage packages. In this regard, the World Health Organization recommends the maximum migration of BPA to foodstuffs as < 0.6 mg kg-1. Analytical BPA determination procedures have been based on chromatographic techniques, which generate waste with organic solvents. Alternatively, proposed spectrophotometric procedures have often shown high detection limits for foodstuffs analysis, requiring pre-concentration prior to determination. The analysis of beverages is susceptible to interferences because of their complex formulation comprising dyes and sugars, for example, that hinder spectrophotometric determinations. Multi-signal calibrations are powerful tools used to minimize matrix effects, and recently, they have proven efficient when performed in flow analysis systems, denominated as multi-dispersion calibration (MDC). This work proposes a multi-pumping flow system for the spectrophotometric determination of BPA based on the reaction with sulfanilamide (used for the first time) after diazotization to yield a compound with an absorption maximum at 446 nm. After the optimization of the main parameters, a linear response was observed between 0.25 and 10 mg L-1. The detection limit (by external calibration), coefficient of variation (n=20), and determination rate were estimated at 0.057 mg L-1, 4.0 %, and 33 h-1, respectively. The MDC was exploited to analyze beverage samples to minimize interferences, especially due to dyes and sucrose. The detection limit estimated for this method was 0.06 mg L-1. Recoveries from 84 to 114 % and the agreement of comparative analysis of the samples with the reference procedure (at the 95% confidence level) demonstrated the accuracy of the proposed procedure. Therefore, the developed alternative is reliable with proper sensitivity and minimum sample preparation for the spectrophotometric determination of BPA in beverages.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Bisphenol A (BPA) is an endocrine disruptor that may be present in plastics and coatings of food and beverage packages. In this regard, the World Health Organization recommends the maximum migration of BPA to foodstuffs as < 0.6 mg kg-1. Analytical BPA determination procedures have been based on chromatographic techniques, which generate waste with organic solvents. Alternatively, proposed spectrophotometric procedures have often shown high detection limits for foodstuffs analysis, requiring pre-concentration prior to determination. The analysis of beverages is susceptible to interferences because of their complex formulation comprising dyes and sugars, for example, that hinder spectrophotometric determinations. Multi-signal calibrations are powerful tools used to minimize matrix effects, and recently, they have proven efficient when performed in flow analysis systems, denominated as multi-dispersion calibration (MDC). This work proposes a multi-pumping flow system for the spectrophotometric determination of BPA based on the reaction with sulfanilamide (used for the first time) after diazotization to yield a compound with an absorption maximum at 446 nm. After the optimization of the main parameters, a linear response was observed between 0.25 and 10 mg L-1. The detection limit (by external calibration), coefficient of variation (n=20), and determination rate were estimated at 0.057 mg L-1, 4.0 %, and 33 h-1, respectively. The MDC was exploited to analyze beverage samples to minimize interferences, especially due to dyes and sucrose. The detection limit estimated for this method was 0.06 mg L-1. Recoveries from 84 to 114 % and the agreement of comparative analysis of the samples with the reference procedure (at the 95% confidence level) demonstrated the accuracy of the proposed procedure. Therefore, the developed alternative is reliable with proper sensitivity and minimum sample preparation for the spectrophotometric determination of BPA in beverages.
Santos, Demetrio J.; Tavares, Lara B.; Antonino, Leonardo D.; Junior, Rogerio R. Sousa; Homem-de-Mello, Paula; Leão, Cedric R.
Kraft lignin-based polyurethanes: Bulk properties, stability and adhesion to native aluminum surfaces Journal Article
Em: Polymer, vol. 309, pp. 127457, 2024, ISSN: 0032-3861.
@article{DOSSANTOS2024127457,
title = {Kraft lignin-based polyurethanes: Bulk properties, stability and adhesion to native aluminum surfaces},
author = {Demetrio J. Santos and Lara B. Tavares and Leonardo D. Antonino and Rogerio R. Sousa Junior and Paula Homem-de-Mello and Cedric R. Leão},
url = {https://www.sciencedirect.com/science/article/pii/S0032386124007936},
doi = {https://doi.org/10.1016/j.polymer.2024.127457},
issn = {0032-3861},
year = {2024},
date = {2024-01-01},
urldate = {2024-01-01},
journal = {Polymer},
volume = {309},
pages = {127457},
abstract = {Lignin as a byproduct from pulp and paper manufacturing has been extensively investigated as raw material for polymer developments. Although, fundamental topics related to the adhesion mechanisms of lignin-based reactive polyurethanes (LPU) still remain unclear. In this work, LPU thin films on native aluminum surface were prepared and characterized. Diluted in THF, employed as the solvent, reactive mixtures of 4,4′-methylene diphenyl isocyanate (4,4′-MDI) and the soluble fraction of three lignins (liquid hydroxypropylated Kraft lignin and two powder Kraft lignins with different pH) were used for LPU thin film deposition via spin coating on aluminum (PVD layer on silicon wafer). The resulting film thickness ranged from 8 nm to several micrometers. The chemical state of the three LPU compositions was assessed in bulk by infrared attenuated total reflectance (IR-ATR) and in the thin films by infrared external reflection absorption spectroscopy (IR-ERAS). Binding energies of 4,4′-methylene diphenyl diisocyanate with aliphatic and aromatic hydroxyl groups were estimated using Density Functional Theory (DFT) simulations. Thus, besides the elucidation of the bulk chemical state of LPUs, the relation to adhesion and stability of LPUs to a native aluminum surface was evaluated. In addition, film topography and homogeneity were monitored by SFM. All lignin types form uniform and homogeneous films. Results revealed a higher consumption of isocyanate groups (NCO) in the formulation with the alkaline Kraft lignin than with the acid one, despite its lower hydroxyl content. A gradient of unreacted NCO was observed in LPU thin films obtained with the powder Kraft lignin types. Residual NCO is also found in thicker films, while the thinnest films did not contain unreacted NCO anymore, indicating the activating effect of the native aluminum surface on LPU formation.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Lignin as a byproduct from pulp and paper manufacturing has been extensively investigated as raw material for polymer developments. Although, fundamental topics related to the adhesion mechanisms of lignin-based reactive polyurethanes (LPU) still remain unclear. In this work, LPU thin films on native aluminum surface were prepared and characterized. Diluted in THF, employed as the solvent, reactive mixtures of 4,4′-methylene diphenyl isocyanate (4,4′-MDI) and the soluble fraction of three lignins (liquid hydroxypropylated Kraft lignin and two powder Kraft lignins with different pH) were used for LPU thin film deposition via spin coating on aluminum (PVD layer on silicon wafer). The resulting film thickness ranged from 8 nm to several micrometers. The chemical state of the three LPU compositions was assessed in bulk by infrared attenuated total reflectance (IR-ATR) and in the thin films by infrared external reflection absorption spectroscopy (IR-ERAS). Binding energies of 4,4′-methylene diphenyl diisocyanate with aliphatic and aromatic hydroxyl groups were estimated using Density Functional Theory (DFT) simulations. Thus, besides the elucidation of the bulk chemical state of LPUs, the relation to adhesion and stability of LPUs to a native aluminum surface was evaluated. In addition, film topography and homogeneity were monitored by SFM. All lignin types form uniform and homogeneous films. Results revealed a higher consumption of isocyanate groups (NCO) in the formulation with the alkaline Kraft lignin than with the acid one, despite its lower hydroxyl content. A gradient of unreacted NCO was observed in LPU thin films obtained with the powder Kraft lignin types. Residual NCO is also found in thicker films, while the thinnest films did not contain unreacted NCO anymore, indicating the activating effect of the native aluminum surface on LPU formation.
2023
Melo, Diego Ulysses; Lima, Henrique Bergonzini; Reis, Roberta Albino; Boaro, Andreia; Pinto, Alexander Garreta Gonçalves Costa; Ciscato, Luiz Francisco Monteiro Leite; Homem-de-Mello, Paula; Bartoloni, Fernando Heering
Em: The Journal of Organic Chemistry, vol. 89, não 1, pp. 345-355, 2023, (PMID: 38113466).
@article{doi:10.1021/acs.joc.3c02079,
title = {Chemiluminescence of a Firefly Luciferin Analogue Reveals that Formation of the Key Intermediate Responsible for Excited State Generation Occurs on a Fully Concerted Step},
author = {Diego Ulysses Melo and Henrique Bergonzini Lima and Roberta Albino Reis and Andreia Boaro and Alexander Garreta Gonçalves Costa Pinto and Luiz Francisco Monteiro Leite Ciscato and Paula Homem-de-Mello and Fernando Heering Bartoloni},
url = {https://doi.org/10.1021/acs.joc.3c02079},
doi = {10.1021/acs.joc.3c02079},
year = {2023},
date = {2023-12-19},
urldate = {2024-01-01},
journal = {The Journal of Organic Chemistry},
volume = {89},
number = {1},
pages = {345-355},
abstract = {The chemiluminescence (CL) reaction of eight different 2-(4-hydroxyphenyl)-4,5-dihydrothiazole-4-carboxylate esters with an organic superbase and oxygen was investigated through a kinetic and computational study. These esters are all analogues to the luciferin substrate involved in efficient firefly bioluminescence. The kinetic data obtained from CL emission and light absorption assays were used in the context of linear free energy relationships (LFER); we obtained the Hammett reaction constant ρ = +1.62 ± 0.09 and the Brønsted constant βlg = −0.39 ± 0.04. These observations from LFER, together with activation parameters obtained from Arrhenius plots, suggest that the formation of the high-energy intermediate (HEI) 1,2-dioxetanone occurs via a concerted mechanism during the rate-determining step of the reaction. Calculations performed using density functional theory support a late transition state for HEI formation within the reaction mechanism pathway, which was described considering geometric parameters, Wiberg bond indices from natural bond order analysis, and the atomic charges derived from the electrostatic potential.},
note = {PMID: 38113466},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The chemiluminescence (CL) reaction of eight different 2-(4-hydroxyphenyl)-4,5-dihydrothiazole-4-carboxylate esters with an organic superbase and oxygen was investigated through a kinetic and computational study. These esters are all analogues to the luciferin substrate involved in efficient firefly bioluminescence. The kinetic data obtained from CL emission and light absorption assays were used in the context of linear free energy relationships (LFER); we obtained the Hammett reaction constant ρ = +1.62 ± 0.09 and the Brønsted constant βlg = −0.39 ± 0.04. These observations from LFER, together with activation parameters obtained from Arrhenius plots, suggest that the formation of the high-energy intermediate (HEI) 1,2-dioxetanone occurs via a concerted mechanism during the rate-determining step of the reaction. Calculations performed using density functional theory support a late transition state for HEI formation within the reaction mechanism pathway, which was described considering geometric parameters, Wiberg bond indices from natural bond order analysis, and the atomic charges derived from the electrostatic potential.
Almeida, James M.; Ferreira, Conny Cerai; Bandeira, Lucas; Cunha, Renato D.; Coutinho-Neto, Maurício Domingues; Homem-de-Mello, Paula; Orestes, Ednilsom; Nascimento, Regina Sandra Veiga
Em: The Journal of Physical Chemistry B, vol. 0, não 0, pp. null, 2023, (PMID: 37871185).
@article{doi:10.1021/acs.jpcb.3c01707,
title = {Synergistic Interaction of Hyperbranched Polyglycerols and Cetyltrimethylammonium Bromide for Oil/Water Interfacial Tension Reduction: A Molecular Dynamics Study},
author = {James M. Almeida and Conny Cerai Ferreira and Lucas Bandeira and Renato D. Cunha and Maurício Domingues Coutinho-Neto and Paula Homem-de-Mello and Ednilsom Orestes and Regina Sandra Veiga Nascimento},
url = {https://doi.org/10.1021/acs.jpcb.3c01707},
doi = {10.1021/acs.jpcb.3c01707},
year = {2023},
date = {2023-10-23},
journal = {The Journal of Physical Chemistry B},
volume = {0},
number = {0},
pages = {null},
abstract = {Applying surfactants to reduce the interfacial tension (IFT) on water/oil interfaces is a proven technique. The search for new surfactants and delivery strategies is an ongoing research area with applications in many fields such as drug delivery through nanoemulsions and enhanced oil recovery. Experimentally, the combination of hyperbranched polyglycerol (HPG) with cetyltrimethylammonium bromide (CTAB) substantially reduced the observed IFT of oil/water interface, 0.9 mN/m, while HPG alone was 5.80 mN/m and CTAB alone IFT was 8.08 mN/m. Previous simulations in an aqueous solution showed that HPG is a surfactant carrier. Complementarily, in this work, we performed classical molecular dynamics simulations on combinations of CTAB and HPG with one aliphatic chain to investigate further the interaction of this pair in oil interfaces and propose the mechanism of IFT decrease. Basically, from our results, one can observe that the IFT reduction comes from a combination of effects that have not been observed for other dual systems: (i) Due to the CTAB-HPG strong interaction, a weakening of their specific and isolated interactions with the water and oil phases occurs. (ii) Aggregates enlarge the interfacial area, turning it into a less ordered interface. (iii) The spread of individual molecules charge profiles leads to the much lower interfacial tension observed with the CTAB+HPG systems.},
note = {PMID: 37871185},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Applying surfactants to reduce the interfacial tension (IFT) on water/oil interfaces is a proven technique. The search for new surfactants and delivery strategies is an ongoing research area with applications in many fields such as drug delivery through nanoemulsions and enhanced oil recovery. Experimentally, the combination of hyperbranched polyglycerol (HPG) with cetyltrimethylammonium bromide (CTAB) substantially reduced the observed IFT of oil/water interface, 0.9 mN/m, while HPG alone was 5.80 mN/m and CTAB alone IFT was 8.08 mN/m. Previous simulations in an aqueous solution showed that HPG is a surfactant carrier. Complementarily, in this work, we performed classical molecular dynamics simulations on combinations of CTAB and HPG with one aliphatic chain to investigate further the interaction of this pair in oil interfaces and propose the mechanism of IFT decrease. Basically, from our results, one can observe that the IFT reduction comes from a combination of effects that have not been observed for other dual systems: (i) Due to the CTAB-HPG strong interaction, a weakening of their specific and isolated interactions with the water and oil phases occurs. (ii) Aggregates enlarge the interfacial area, turning it into a less ordered interface. (iii) The spread of individual molecules charge profiles leads to the much lower interfacial tension observed with the CTAB+HPG systems.
Corrêa, Raissa Lohanna Gomes Quintino; Moraes, Matheus Morato Ferreira; Oliveira, Kléber Thiago; Aoto, Yuri Alexandre; Coutinho-Neto, Maurício Domingues; Homem-de-Mello, Paula
Diving into the optoelectronic properties of Cu(II) and Zn(II) curcumin complexes: a DFT and wavefunction benchmark Journal Article
Em: J Mol Model, vol. 29, não 5, 2023, ISSN: 0948-5023.
@article{Corrêa2023,
title = {Diving into the optoelectronic properties of Cu(II) and Zn(II) curcumin complexes: a DFT and wavefunction benchmark},
author = {Raissa Lohanna Gomes Quintino Corrêa and Matheus Morato Ferreira Moraes and Kléber Thiago Oliveira and Yuri Alexandre Aoto and Maurício Domingues Coutinho-Neto and Paula Homem-de-Mello},
doi = {10.1007/s00894-023-05560-1},
issn = {0948-5023},
year = {2023},
date = {2023-05-01},
journal = {J Mol Model},
volume = {29},
number = {5},
publisher = {Springer Science and Business Media LLC},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Souza, Jhonathan R.; Curutchet, Carles; Aoto, Yuri A.; Homem-De-Mello, Paula
Benchmarking DFT functionals for photophysics of pyranoflavylium cations Journal Article
Em: Journal of Molecular Graphics and Modelling, vol. 122, pp. 108460, 2023, ISSN: 1093-3263.
@article{SOUZA2023108460,
title = {Benchmarking DFT functionals for photophysics of pyranoflavylium cations},
author = {Jhonathan R. Souza and Carles Curutchet and Yuri A. Aoto and Paula Homem-De-Mello},
url = {https://www.sciencedirect.com/science/article/pii/S109332632300058X},
doi = {https://doi.org/10.1016/j.jmgm.2023.108460},
issn = {1093-3263},
year = {2023},
date = {2023-01-01},
journal = {Journal of Molecular Graphics and Modelling},
volume = {122},
pages = {108460},
abstract = {An intense absorption, phosphorescence, a long triplet excited state lifetime and singlet oxygen generation capabilities are characteristics of pyranoflavylium cations, analogues to pyranoanthocyanidins originated in the maturation process of red wine. Such properties make these compounds potential photosensitizers to be applied in photodynamic therapy. In this context, the photophysical processes underlying that treatment critically depend on the electronic structure of the pyranoflavylium molecules. When employing density functional theory to describe the electronic structure of molecules, the choice of the most suitable functional is not trivial, and benchmark studies are needed to orient practitioners in the field. In this work, a benchmark of seven of the most commonly used density functionals in addressing the photophysical properties of a set of eight pyranoflavylium cations is reported. Ground and excited state geometries, molecular orbitals, and absorption, fluorescence and phosphorescence transition energies were calculated using density functional theory approaches, and evaluated and compared to experimental data and monoreferential wave function-based methodologies. Statistical analysis of the results indicates that global-hybrid functionals allow an excellent description of absorption and emission energies, with errors around 0.05 eV, while range-separated variants led to somewhat larger errors in the range 0.1–0.2 eV. In contrast, range-separated functionals display excellent phosphorescence energies with errors close to 0.05 eV, in this case global-hybrids showing increased discrepancies around 0.5–0.1 eV.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
An intense absorption, phosphorescence, a long triplet excited state lifetime and singlet oxygen generation capabilities are characteristics of pyranoflavylium cations, analogues to pyranoanthocyanidins originated in the maturation process of red wine. Such properties make these compounds potential photosensitizers to be applied in photodynamic therapy. In this context, the photophysical processes underlying that treatment critically depend on the electronic structure of the pyranoflavylium molecules. When employing density functional theory to describe the electronic structure of molecules, the choice of the most suitable functional is not trivial, and benchmark studies are needed to orient practitioners in the field. In this work, a benchmark of seven of the most commonly used density functionals in addressing the photophysical properties of a set of eight pyranoflavylium cations is reported. Ground and excited state geometries, molecular orbitals, and absorption, fluorescence and phosphorescence transition energies were calculated using density functional theory approaches, and evaluated and compared to experimental data and monoreferential wave function-based methodologies. Statistical analysis of the results indicates that global-hybrid functionals allow an excellent description of absorption and emission energies, with errors around 0.05 eV, while range-separated variants led to somewhat larger errors in the range 0.1–0.2 eV. In contrast, range-separated functionals display excellent phosphorescence energies with errors close to 0.05 eV, in this case global-hybrids showing increased discrepancies around 0.5–0.1 eV.
