One-electron addition on short-loop selenylsulfide and diselenide-linked biomolecules: From diethyldichalcogens to Grx3-like selenopeptides

摘要

One-electron uptake by thiaselenide or diselenide linkages of a series of short-loop selenopeptides, is examined by means of hybrid QM:QM′ and QM:MM calculations. A special emphasis is given to the identification of key factors tuning adiabatic electron affinity, in comparison with established trends for disulfides. The conclusions are threefold: first, electron capture is intrinsically favored by 0.20 and 0.36 eV upon sulfur-to-selenium mono- or bi-substitution. This order of reactivity, established on diethyldichalcogens, is globally transferable to linear dipeptides, with a dramatic increase of ～1eV of adiabatic electron affinities. Cyclization impact is then quantified along a representative set of short-loop peptides: conformational strain tends to reinforce dichalcogen propensity to act as an "electron buffer," although this contribution is attenuated for seleno-containing linkages because of their longer equilibrium distance. Collective electrostatic effects, such as the dipole created by a N-terminal α-helix, result in the same shifting, e.g., ～1eV as a dodecalanine is grafted onto a given tetrapeptide. Structural features for neutral and radical anion species are also analyzed, in line with their spectroscopic aftermaths. This analysis delineates some useful trends for assisting design of seleno agents and artificial enzymes.