Article ID Journal Published Year Pages File Type
5371241 Biophysical Chemistry 2012 12 Pages PDF
Abstract

Due to the high importance of the structural properties of peptides, the conformational behavior of one of their elementary building blocks, asparagine, has been investigated in this work. Matrix-isolation FT-IR spectroscopy is a suitable technique to investigate the intrinsic properties of small molecules. Asparagine has been subjected to matrix-isolation FT-IR spectroscopy supported with DFT and MP2 calculations. DFT optimization of asparagine resulted in 10 stable conformations with ∆EDFT < 10 kJ.mol− 1. Compared to a previous study, one new conformation has been revealed. Further optimization at the MP2/6-31++G** level resulted in seven conformations with ∆EMP < 10 kJ.mol− 1. A conformation containing the three intramolecular H-bonds, i.e. C = Osc…HNbb, C = Obb…HNsc and OHbb…Nbb appeared to be the most stable one at both levels despite the large negative entropy contribution due to these 3 H-bonds. At the sublimation temperature of 353 K, the DFT method predicts four and the MP2 method six conformations to be present in the experimental matrix-isolation spectrum. These conformations have different intramolecular H-bonds, which has allowed to identify at least 4 low energy conformations in the FT-IR spectrum. Detailed comparison between theory and experiment resulted in a mean frequency deviation of 7.6 cm− 1.

Graphical abstractDownload full-size imageHighlights► Ab initio exploration of the conformational landscape of asparagine. ► Three intramolecular H-bonds in the most stable form. ► A strong H-bond interaction between the side chain and the backbone. ► Experimental identification by matrix-isolation FT-IR spectroscopy. ► A mean frequency deviation of 7.6 cm− 1.

Related Topics
Physical Sciences and Engineering Chemistry Physical and Theoretical Chemistry
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