title: Temperature dependence of amino acid side chain IR absorptions in the amide I' region.
abstract: Amide I' IR spectra are widely used for studies of structural changes in peptides and proteins as a function of temperature. Temperature dependent absorptions of amino acid side-chains that overlap the amide I' may significantly complicate the structural analyses. While the side-chain IR spectra have been investigated previously, thus far their dependence on temperature has not been reported. Here we present the study of the changes in the IR spectra with temperature for side-chain groups of aspartate, glutamate, asparagine, glutamine, arginine, and tyrosine in the amide I' region (in D2O). Band fitting analysis was employed to extract the temperature dependence of the individual spectral parameters, such as peak frequency, integrated intensity, band width, and shape. As expected, the side-chain IR bands exhibit significant changes with temperature. The majority of the spectral parameters, particularly the frequency and intensity, show linear dependence on temperature, but the direction and magnitude vary depending on the particular side-chain group. The exception is arginine, which exhibits a distinctly nonlinear frequency shift with temperature for its asymmetric CN3H5(+) bending signal, although a linear fit can account for this change to within ~1/3 cm(-1). The applicability of the determined spectral parameters for estimations of temperature-dependent side-chain absorptions in peptides and proteins are discussed.
authors.affiliation: Department of Chemistry, University of Wyoming, 1000 E University Ave, Laramie, WY, 82071.
authors.forename: Benjamin A
authors.initials: BA
authors.lastname: Anderson
authors.forename: Alex
authors.initials: A
authors.lastname: Literati
authors.forename: Borden
authors.initials: B
authors.lastname: Ball
authors.forename: Jan
authors.initials: J
authors.lastname: Kubelka
mesh_terms: D065966:Absorption, Physicochemical; D000577:Amides / Q000737:chemistry*; D000596:Amino Acids / Q000737:chemistry*; D002264:Carboxylic Acids / Q000737:chemistry; D017666:Deuterium Oxide / Q000737:chemistry; D004952:Esters / Q000737:chemistry; D008958:Models, Molecular; D013055:Spectrophotometry, Infrared; D013696:Temperature
chemical_list: D000577:Amides; D000596:Amino Acids; D002264:Carboxylic Acids; D004952:Esters; D017666:Deuterium Oxide
keywords: bandshape; frequency; infrared spectroscopy; intensity; peptide; protein