Atomic polarizability dominates the electronic properties of peptide bonds upon thioxo or selenoxo substitution. Academic Article uri icon

Overview

abstract

  • The amide bond as peptide linkage plays an important role in protein structure and function. A large number of theoretical and experimental studies have focused on the specific nature of the peptide bond. Little attention, however, has been paid to their chalcogen-substituted congeners, although experimental data on thioamides revealed inconsistencies with the conventional view of amide resonance theory. Here, we employed thioxo and selenoxo substitution to determine experimentally how heavier chalcogens affect the properties of the peptide bond and adjacent atoms. NMR data revealed pronounced deshielding of heteronuclei within a three-bond distance to the chalcogen atom; this indicates an enhanced electron-withdrawing potential of the heavier chalcogens despite their lower electronegativities compared to oxygen. Interestingly, linear correlations were observed between chalcogen atomic polarizability and the chemical shift values of those neighboring heteronuclei as well as several physicochemical properties, such as electronic excitation energy, C-N rotation barrier, dipole moment and amide proton dissociation. We conclude that the chalcogen polarizability, which relates to the charge capacity, is the dominant factor that determines the electronic properties of peptide bonds substituted with heavier chalcogens.

publication date

  • July 10, 2012

Research

keywords

  • Chalcogens
  • Oxygen
  • Peptides
  • Sulfur
  • Thioamides

Identity

Scopus Document Identifier

  • 84864435721

Digital Object Identifier (DOI)

  • 10.1002/chem.201200863

PubMed ID

  • 22782859

Additional Document Info

volume

  • 18

issue

  • 32