Density functional theoretical studies on electronic structural, optical and oxidation properties of thioxylated peptides

Abstract

Thioxylated peptide bond in simple dipeptides and tripeptides is found to amend the structural, optical and redox properties of the same relying on the position of substitution (N- and C-terminals). The electronic structural investigations show that the geometrical parameters are found to be highly influenced by the thioxo substitution at N-terminus. However, the absorbance properties are influenced by thioxo substitution at C-terminal, where blue shifts in π–π* transitions are observed compared to unsubstituted one. Similarly, the cationization reveals that the substitution at C-terminal promotes the conformational shift. Further, the computational studies clearly indicate that the N-terminal substitution effects the ground state geometry, while substitution at other position influences the excited and redox properties. The observed conformation switches in C-terminal conformers have been proposed as a candidate for redox switch, where the states (neutral and cation) were probed using computed vibrational data and chemical shift values.