Formation of n → π+interaction facilitating dissociative electron transfer in isolated tyrosine-containing molecular peptide radical cations

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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Author(s)

  • Xiaoyan Mu
  • Mengzhu Li
  • Jonathan Martens
  • Giel Berden
  • Jos Oomens
  • Ivan K. Chu

Related Research Unit(s)

Detail(s)

Original languageEnglish
Pages (from-to)21393-21402
Journal / PublicationPhysical Chemistry Chemical Physics
Volume22
Issue number37
Online published7 Sep 2020
Publication statusPublished - 7 Oct 2020

Abstract

Long-range electron transfer in proteins can be rationalized as a sequential short-distance electron-hopping processes via amino acid residues having low ionization energy as relay stations. Tyrosine residues can serve as such redox-active intermediates through one-electron oxidation to form a π-radical cation at its phenol side chain. An electron transfer from a vicinal functional group to this π-electron hole completes an elementary step of charge migration. However, transient oxidized/reduced intermediates formed at those relay stations during electron transfer processes have not been observed. In this study, formation of analog reactive intermediates via electron donor-acceptor coupling is observed by using IRMPD action spectroscopy. An elementary charge migration at the molecular level in model tyrosine-containing peptide radical cations [M]in the gas phase is revealed with its unusual Cα-Cβ bond cleavage at the side chain of the N-terminal residue. This reaction is induced by the radical character of the N-terminal amino group (-NH2+) resulting from an n → πinteraction between the nonbonding electron pair of NH2(n) and the π-electron hole at the Tyr side chain (π+). The formation of -NH2is supported by the IRMPD spectrum showing a characteristic NHscissor vibration coupled with Tyr side-chain stretches at 1577 cm−1. This n → πinteraction facilitates a dissociative electron transfer with NHas the relay station. The occurrence of this side-chain cleavage may be an indicator of the formation of reactive conformers featuring the n → πinteraction.

Citation Format(s)

Formation of n → π+interaction facilitating dissociative electron transfer in isolated tyrosine-containing molecular peptide radical cations. / Tang, Wai Kit; Mu, Xiaoyan; Li, Mengzhu; Martens, Jonathan; Berden, Giel; Oomens, Jos; Chu, Ivan K.; Siu, Chi-Kit.

In: Physical Chemistry Chemical Physics, Vol. 22, No. 37, 07.10.2020, p. 21393-21402.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review