Please use this identifier to cite or link to this item:
|Title:||Matrix-Isolated Monomeric Tryptophan: Electrostatic Interactions as Nontrivial Factors Stabilizing Conformers||Authors:||Kaczor, A.
Reva, I. D.
Proniewicz, L. M.
|Issue Date:||24-Mar-2007||Publisher:||American Chemical Society||Serial title, monograph or event:||J. Phys. Chem. A||Volume:||111||Abstract:||An extensive analysis of the conformational space of tryptophan (Trp) was performed at the B3LYP/6-311++G(d,p) level and verified by comparison with the infrared spectra of the compound isolated in low-temperature argon and xenon matrixes. Different types of conformers have been unequivocally identified in the matrixes. Type I exhibits the trans arrangement of the carboxylic group and is stabilized by an O−H···N intramolecular H-bond. Types II and III have the carboxylic group in the cis conformation and feature N−H···OC and N−H···O−C hydrogen bonds, respectively. Three individual conformers of type I were identified in the matrixes. Other conformational degrees of freedom are related with the Cα−Cβ−CγC and C1−Cα−Cβ−Cγ angles (χ1 and χ2, respectively). In proteins, these two dihedral angles define the conformations of the amino acid residues. In monomeric Trp, χ1 adopts the “+” (ca. +90°) and “−” (ca. −90°) orientations, while average values of −67.4, 170.5, and 67.6° (“a”, “b”, and “c”, respectively) were found for χ2. Theoretical analysis revealed two important factors in stabilizing the structures of the Trp conformers: the H-bond type and electrostatic interactions. Classified by the H-bond type, the most stable are forms I, followed by II and III. Out of possible combinations of the χ1 and χ2 dihedral angles, “a+”, “b+”, and “c−” were theoretically found more stable than their “a−”, “b−”, and “c+” counterparts. Thus, the stabilizing effect of interactions involving the pyrrole ring (which are possible in Ia+, Ib+, and Ic− conformers) is considerably higher compared to those in which the phenyl ring is engaged (existing in the Ia−, Ib−, and Ic+ forms).||URI:||http://hdl.handle.net/10316/17922||DOI:||10.1021/jp070097c||Rights:||openAccess|
|Appears in Collections:||FCTUC Química - Artigos em Revistas Internacionais|
Show full item record
Files in This Item:
|J.Physical Chemistry A, 111 (2007) 2957.pdf||279.1 kB||Adobe PDF||View/Open|
checked on May 29, 2020
WEB OF SCIENCETM
checked on Sep 2, 2021
Page view(s) 50397
checked on Sep 24, 2021
checked on Sep 24, 2021
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.