Revised conformational assignments and conformational evolution of tyrosine by laser desorption supersonic jet laser spectroscopy

Abstract

The number of conformers and their structures of tyrosine are reassigned on the basis of resonance enhanced multiphoton ionization (REMPI), ultraviolet-ultraviolet hole burning (UV-UV HB), infrared (IR) dip spectra, and quantum chemical calculations. From comparison between REMPI and UV-UV HB spectra, it was found that 12 conformers coexist in the supersonic jet. The structures of these conformers are determined by the IR spectra and theoretical calculations. The number of conformers is more than that reported in the previous reports (8 conformers), and is rationalized by the systematic formation of conformers from simpler molecules without substituents, just like evolution. The importance of dipole-dipole interaction between an amino-acid chain and hydroxyl group at the benzene ring was also discussed.

Isolated Neutral Peptides

“…NH and OH stretch signatures [16,20,26,28,56,74,77,79,88,89,95,96,101,106,113,137,138,140]. Other studies [22-25, 66, 69, 75, 97, 142] have also illustrated the flexibility of these terminations, giving rise to several OH-N or NH-O bonds.…”

“…Phe-containing dipeptides have been confidently assigned without relying on quantum calculations, and a ranking of the H-bonds according to their strength has been proposed (C5<NH-π<C10<C7 [34]). This pioneering work paved the way to systematic tests of quantum chemical methods in their ability to reproduce the IR spectra of these species as well as the conformer [26,28,31,46,63,95,113], although recent advances seem to be promising [147,148].…”

UV–UV hole burning and IR dip spectroscopy of homophenylalanine by laser desorption supersonic jet technique

“…4 together with its structural notation. Here, we used the similar notations to those used for tyrosine [3] and dopa [27] as follows.…”

“…Particularly the aromatic amino acids, phenylalanine (Phe) [2,9,22,23], tyrosine (Tyr) [1,3,24] and tryptophan (Trp) [7,8] have been investigated by many groups because of their near UV absorption and unique inter/intramolecular interactions due to the aromatic ring. According to the former reports, Phe, Tyr and Trp have 6, 12 and 6 conformers in the gas phase and their structures were assigned successfully by the combination of IR-UV double resonance spectroscopy and quantum chemical calculations [3,6,7]. On the other hand, any spectroscopic information of their derivatives has not been reported in spite of their importance.…”

The Rotational Spectrum of Tyrosine

“…Hence, these techniques have been applied to tyrosine (Tyr), tryptophan (Trp), and phenylalanine (Phe), which were the subject of a large number of investigations. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] REMPI and LIF experiments on Tyr [12][13][14][15] reported up to ten vibronic bands which suggested the presence of a large number of stable conformers. More recently, eight different structures of Tyr were confirmed by using UV-UV and IR-UV hole burning techniques.…”