Conformational Analysis of Gly鈥揂la鈥揘HMe in D2O and DMSO Solutions: A Two-Dimensional Infrared Spectroscopy Study
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- 作者：Marco Candelaresi ; Elena Ragnoni ; Chiara Cappelli ; Alessandro Corozzi ; Manuela Lima ; Susanna Monti ; Benedetta Mennucci ; Francesca Nuti ; Anna Maria Papini ; Paolo Foggi
- 刊名：Journal of Physical Chemistry B
- 出版年：2013
- 出版时间：November 21, 2013
- 年：2013
- 卷：117
- 期：46
- 页码：14226-14237
- 全文大小：556K
- 年卷期：v.117,no.46(November 21, 2013)
- ISSN：1520-5207
文摘
A relevant number of experiments on short peptides has been performed in recent years. One of the major problems rises from the simultaneous presence of slightly different conformers at equilibrium in solution. In the present paper, the conformational characteristics of the Gly鈥?span class="smallcaps">l-Ala鈥揗ethyl amide dipeptide in D2O and DMSO solutions are investigated by nonlinear IR spectroscopy. The pump鈥損robe scheme with ultrashort mid-infrared pulses, in the Amide I region, is used to determine the mutual orientation of the two C鈺怬 bonds and the dynamics due to solute鈥搒olvent interactions. The coupling between Amide I modes is evaluated from both linear and 2D spectra. The interconversion between the different conformations occurs on time scales longer than the vibrational lifetime, and the spectral diffusion observed in 2D spectra is attributed to the solvent dynamics. Quantum mechanical calculations and molecular dynamics simulations are performed to identify the most stable geometries. By comparing the experimental and the theoretical data, we establish the prevalence of 尾-like polar conformers in both water and DMSO solvents.