10.1021/jp8076358.s001 Sergej Naumov Sergej Naumov Christian Schöneich Christian Schöneich Intramolecular Addition of Cysteine Thiyl Radical to Phenylalanine and Tyrosine in Model Peptides, Phe (CysS<sup>•</sup>) and Tyr(CysS<sup>•</sup>): A Computational Study American Chemical Society 2009 thiyl radicals Computational StudyDensity Functional Theory Phe calculation complex HS Tyr DFT Cysteine Thiyl Radical CysS 2009-04-16 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Intramolecular_Addition_of_Cysteine_Thiyl_Radical_to_Phenylalanine_and_Tyrosine_in_Model_Peptides_Phe_CysS_sup_sup_and_Tyr_CysS_sup_sup_A_Computational_Study/2863243 Density Functional Theory (DFT) calculations were carried out to evaluate the potential for <i>intra</i>molecular addition of peptide cysteine (Cys) thiyl radicals (CysS<sup>•</sup>) to aromatic amino acids (Phe and Tyr) in water. These calculations yielded cyclic conformations, in which π-complexes were more stable than cyclohexadienyl radicals in water. In these π-complexes, the C<sub>2</sub>−S distances were significantly shorter compared to the C<sub>1</sub>−S and C<sub>3</sub>−S distances. Comparable results on the relative stabilities were obtained for model calculations for the addition of HS<sup>•</sup>/CH<sub>3</sub>S<sup>•</sup> to toluene and <i>p</i>-hydroxytoluene. The adduct of thiyl radicals with Phe was more stable than that with Tyr, and the stabilization energies depended on the C-terminal substituents.