Raman spectral analysis in the C-H stretching region of proteins and amino acids for investigation of hydrophobic interactions.
Raman spectra of amino acids showed complexity in the C-H stretching region (2800-3100 cm(-)(1)) attributed to diversity of CH, CH(2), and CH(3) groups in the side chains, ionization state, and microenvironment. The involvement of specific amino acids in the C-H stretching region of selected proteins, namely, lysozyme, alpha-lactalbumin, beta-lactoglobulin, and their binary mixtures, was investigated by deconvolution using maximum likelihood techniques. The main protein band near 2940 cm(-)(1) was attributed not only to aromatic and aliphatic amino acids but also to many other amino acids. A band near 3065 cm(-)(1) was assigned to aromatic residues, whereas bands near 2880 and 2900 cm(-)(1) corresponded primarily to aliphatic amino acids. Heating at 90 degrees C increased relative intensity near 2940 cm(-)(1) and decreased relative intensity at 2895-2902 cm(-)(1) for lysozyme and its mixtures with alpha-lactalbumin or beta-lactoglobulin. Additional bands at 2812 or 2838 and 3003 cm(-)(1) were observed after heating or in 8 M deuterated urea, reflecting changes upon denaturation.
Howell
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NK
School of Biological Sciences, University of Surrey, Guildford, Surrey, United Kingdom GU2 5XH.
Arteaga
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G
Nakai
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S
Li-Chan
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EC
D000596:Amino Acids / Q000737:chemistry*; D002244:Carbon; D006859:Hydrogen; D007768:Lactalbumin / Q000737:chemistry; D007782:Lactoglobulins / Q000737:chemistry; D016013:Likelihood Functions; D009113:Muramidase / Q000737:chemistry; D011506:Proteins / Q000737:chemistry*; D013059:Spectrum Analysis, Raman / Q000379:methods
D000596:Amino Acids; D007782:Lactoglobulins; D011506:Proteins; D002244:Carbon; D006859:Hydrogen; D007768:Lactalbumin; D009113:Muramidase