Intramolecular addition of cysteine thiyl radical to phenylalanine and tyrosine in model peptides, Phe (CysS*) and Tyr(CysS*): a computational study.
Density Functional Theory (DFT) calculations were carried out to evaluate the potential for intramolecular addition of peptide cysteine (Cys) thiyl radicals (CysS(*)) to aromatic amino acids (Phe and Tyr) in water. These calculations yielded cyclic conformations, in which pi-complexes were more stable than cyclohexadienyl radicals in water. In these pi-complexes, the C(2)-S distances were significantly shorter compared to the C(1)-S and C(3)-S distances. Comparable results on the relative stabilities were obtained for model calculations for the addition of HS(*)/CH(3)S(*) to toluene and p-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.
Naumov
Sergej
S
Leibniz-Institut für Oberflächenmodifizierung, e. V., Permoserstrasse 15, D-04318 Leipzig, Germany. sergej.naumov@iom-leipzig.de
Schöneich
Christian
C
D003198:Computer Simulation; D003545:Cysteine / Q000031:analogs & derivatives* / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D010455:Peptides / Q000737:chemistry*; D010649:Phenylalanine / Q000737:chemistry*; D011789:Quantum Theory; D014443:Tyrosine / Q000737:chemistry*; D014867:Water / Q000737:chemistry
D010455:Peptides; D014867:Water; D014443:Tyrosine; D010649:Phenylalanine; D003545:Cysteine