Conformational structure of the central nervous system proteolipid apoprotein. A Raman and infrared spectroscopic study

Abstract Raman and infrared spectroscopy have been applied to investigate the structure of proteolipid apoprotein, PLA, in the solid state. These techniques reveal the presence of α-helical, β-sheet and unordered structures through the amide A, I, II, III and V bands. A fitting program for resolution of infrared amide I band provided an estimate of the protein secondary structure including 39% α-helix, 36% β-sheet and 25% coil and turns. PLA displays higher content of β and unordered structures than non-delipidated proteolipid PLP which, however, is more rich in α-helical segments. The Raman spectra also reveal the hydrogen-bonding environments of tyrosine residues in this protein. These residues are known from these Raman spectra to be exposed on the protein surface.