Issue 41, 2010

Mass-spectrometric and computational study of tryptophan radicals (Trp + H)˙ produced by collisional electron transfer to protonated tryptophan in the gas phase

Abstract

Hydrogen atom adducts to tryptophan were generated for the first time in the gas phase by collisional electron transfer to protonated tryptophan at 7170 eV kinetic energy. The radicals showed fast dissociations by CαCβ bond cleavage and cross-ring cleavages occurring on the 7.3 μs time scale. The mechanism of the CαCβ bond cleavage was explained by ab initio computational analysis of the radical potential energy surface. This showed spontaneous isomerization of the primary tryptophan radical by ammonium hydrogen atom migration to the carboxyl group. The stable intermediate formed by the isomerization can undergo radical-induced scission of the CαCβ bond in competition with H-atom migrations to the C-2 and C-4 positions of the indole ring. RRKM calculations of unimolecular rate constants on the B3-ROMP2/6-311++G(2d,p) potential energy surface indicated that the CαCβ bond cleavage was the fastest unimolecular reaction of the radical intermediates within the range of internal energies acquired upon electron transfer. We also report an updated G2(MP2) proton affinity of tryptophan (PA = 946 kJ mol−1) and hydrogen atom affinities of the tryptophan indole ring of relevance to electron-based peptide dissociations.

Graphical abstract: Mass-spectrometric and computational study of tryptophan radicals (Trp + H)˙ produced by collisional electron transfer to protonated tryptophan in the gas phase

Supplementary files

Article information

Article type
Paper
Submitted
17 May 2010
Accepted
02 Aug 2010
First published
08 Sep 2010

Phys. Chem. Chem. Phys., 2010,12, 13434-13447

Mass-spectrometric and computational study of tryptophan radicals (Trp + H)˙ produced by collisional electron transfer to protonated tryptophan in the gas phase

J. A. Gregersen and F. Tureček, Phys. Chem. Chem. Phys., 2010, 12, 13434 DOI: 10.1039/C0CP00597E

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements