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Ionization of the Conformers of cis Nanotubular Cyclic Peptides in the Gas Phase: Effect of Size and Conformation on Ionization
Author(s) -
Karachi Sara,
Farrokhpour Hossein,
Abyar Fatemeh
Publication year - 2018
Publication title -
journal of the chinese chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.329
H-Index - 45
eISSN - 2192-6549
pISSN - 0009-4536
DOI - 10.1002/jccs.201700179
Subject(s) - chemistry , conformational isomerism , ionization , ionization energy , lone pair , electron ionization , x ray photoelectron spectroscopy , crystallography , molecule , computational chemistry , ion , organic chemistry , nuclear magnetic resonance , physics
Cyclic peptides, because of their unique spatial conformations, simplicity, and limited conformational freedom, are widely used as model molecules for larger peptides in chemistry and biochemistry. In this work, the ionization energies and photoelectron spectra of different conformers of the cyclic peptides ( n = 2–15) were calculated using the symmetry‐adapted cluster‐configuration interaction (SAC‐CI) method and D95 + (d,p) basis set in the gas phase. The calculated photoelectron spectra were used to study the electronic structures of the cyclic peptides. It was observed that the first ionization energy of the cyclic peptides decreases with the ring size, reaches a minimum, and then increases. In addition, the first ionization band of the cyclic peptides was assigned to the ionization of the lone electron pairs of the nitrogen atoms, although there are π electrons of the CO bond and the lone electron pairs of oxygen atoms in the structure of the peptides.