Chemical Representation Dependence of Quinone Reduction Energetics: Site-Specific Limits of Methylthio Surrogates for Cysteine-Derived Conjugates
- 1Stanford Online High School, 415 Broadway, Redwood City, California, 94063
Abstract
Methylthio substituents are compact models for larger sulfur-linked quinone conjugates, yet their fidelity for calculated one-electron reduction-energy shifts is uncertain. We audited a historical survey of 38 methylthio attachment sites in 26 quinones; four source-energy outputs remain unreconciled, leaving 34 archive-corroborated site shifts across 25 parents. In a historical matched comparison of ten SMe and N-acetylcysteine methyl ester-derived (AcCysOMe) conjugate models, the original median absolute mismatch was 0.175900 eV. An explicitly retrospective, source-corroborated eightsite subset retained a median mismatch of 0.162917 eV, above the prespecified 0.05 eV screening tolerance, with category agreement of 1/3 among decisive SMe cases. Four separately conformercorrected case studies included opposite-sign shifts for benz[a]anthracene-3,4-dione and its 7-methyl analogue. An alternative-functional PBE0-D4 fixed-geometry analysis retained both numerical sign differences, although the 7-methyl analogue's AcCysOMe shift (−0.037065 eV) was near zero under the original category rule. Retrospective spin-population checks indicated predominantly quinonecentered radical-anion states. Thus, sulfur-fragment truncation can materially alter a computed site-
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BibTeX
@misc{tsai2026chemical,
title = {{Chemical Representation Dependence of Quinone Reduction Energetics: Site-Specific Limits of Methylthio Surrogates for Cysteine-Derived Conjugates}},
author = {Aris Tsai},
howpublished = {ChemRxiv},
year = {2026},
month = oct,
doi = {10.26434/chemrxiv.15010764/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010764/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Chemical Representation Dependence of Quinone Reduction Energetics: Site-Specific Limits of Methylthio Surrogates for Cysteine-Derived Conjugates
AU - Aris Tsai
PY - 2026
DA - 2026/10/21
PB - ChemRxiv
DO - 10.26434/chemrxiv.15010764/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010764/v1
AB - Methylthio substituents are compact models for larger sulfur-linked quinone conjugates, yet their fidelity for calculated one-electron reduction-energy shifts is uncertain. We audited a historical survey of 38 methylthio attachment sites in 26 quinones; four source-energy outputs remain unreconciled, leaving 34 archive-corroborated site shifts across 25 parents. In a historical matched comparison of ten SMe and N-acetylcysteine methyl ester-derived (AcCysOMe) conjugate models, the original median absolute mismatch was 0.175900 eV. An explicitly retrospective, source-corroborated eightsite subset retained a median mismatch of 0.162917 eV, above the prespecified 0.05 eV screening tolerance, with category agreement of 1/3 among decisive SMe cases. Four separately conformercorrected case studies included opposite-sign shifts for benz[a]anthracene-3,4-dione and its 7-methyl analogue. An alternative-functional PBE0-D4 fixed-geometry analysis retained both numerical sign differences, although the 7-methyl analogue's AcCysOMe shift (−0.037065 eV) was near zero under the original category rule. Retrospective spin-population checks indicated predominantly quinonecentered radical-anion states. Thus, sulfur-fragment truncation can materially alter a computed site-
ER -