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Thermal Stability of Dehydrophenylalanine‐Containing Model Peptides as Probed by Infrared Spectroscopy: a Case Study of an α ‐Helical and a 3 10 ‐Helical Peptide
Author(s) -
Gupta Alka,
Mehrotra Ranjana,
Klimov Evgueni,
Siesler Heinz Wilhelm,
Joshi Ratanmani M.,
Chauhan Virander Singh
Publication year - 2006
Publication title -
chemistry and biodiversity
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.427
H-Index - 70
eISSN - 1612-1880
pISSN - 1612-1872
DOI - 10.1002/cbdv.200690031
Subject(s) - chemistry , intramolecular force , peptide , protein secondary structure , infrared spectroscopy , amide , residue (chemistry) , crystallography , thermal stability , spectroscopy , circular dichroism , infrared , stereochemistry , fourier transform infrared spectroscopy , organic chemistry , biochemistry , physics , quantum mechanics , optics
The temperature‐dependent secondary‐structural changes in the two known helical model peptides Boc‐Val‐ΔPhe‐Ala‐Leu‐Gly‐OMe ( 1 ; α ‐helical) and Boc‐Leu‐Phe‐Ala‐ΔPhe‐Leu‐OMe ( 2 ; 3 10 ‐helical), which both comprise a single dehydrophenylalanine (ΔPhe) residue, were investigated by means of FT‐IR spectroscopy (peptide film on KBr). Both the first‐order and the better‐resolved second‐order derivative IR spectra of 1 and 2 were analyzed. The ν (NH) (3240–3340 cm −1 ), the Amide‐I (1600–1700 cm −1 ), and the Amide‐II (1510–1580 cm −1 ) regions of 1 and 2 showed significant differences in thermal‐denaturation experiments (22°→144°), with the 3 10 ‐helical peptide ( 2 ) being considerably more stable. This observation was rationalized by different patterns and strengths of intramolecular H‐bonds, and was qualitatively related to the different geometries of the peptides. Also, a fair degree of residual secondary‐structural elements were found even in the ‘denatured’ states above 104° ( 1 ) or 134° ( 2 ).