Eur. Phys. J. D (2014) 68: 68
https://doi.org/10.1140/epjd/e2014-40826-y

Regular Article

VUV photofragmentation of protonated leucine-enkephalin peptide dimer below ionization energy^*

¹ Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia
² INRA, UMR1324 Centre des Sciences du Goût et de l’Alimentation, 21000 Dijon, France
³ Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, 91192 Gif-sur-Yvette, France
⁴ UAR 1008 CEPIA, INRA, 44316 Nantes, France

^a e-mail: vraz@ipb.ac.rs

Received: 23 December 2013
Received in final form: 28 January 2014
Published online: 25 March 2014

Abstract

The experimental investigation of 5–8 eV photons induced dissociation of the leucine-enkephalin (Leu-Enk) peptide dimer, performed by coupling a linear ion trap with a synchrotron beamline, in combination with the tandem mass spectrometry, has been reported. The present work extends the existing results on Leu-Enk VUV-induced dissociation to lower sub-ionization photon energy range. The measured tandem mass spectra show that even at the photon energies below the ionization threshold, VUV irradiation of the protonated Leu-Enk dimer precursor can lead to a rich fragmentation pattern, including peptide sequence ions and neutral losses. The photodissociation yields of selected ionic fragments reveal the absorption bands at about 6.7–7.1 eV (185–175 nm). The experimental results have been supported by theoretical description of the [2Leu-Enk + H]⁺ precursors, optimized at B3LYP/6-31+G(d,p) level of DFT.