STRUCTURAL STUDY OF HUMAN VERY-LOW-DENSITY LIPOPROTEINS BY INFRARED-SPECTROSCOPY

The secondary structure of human very low density lipoproteins (VLDL) has been quantitatively examined by using Fourier transform infrared ( FTIR) spectroscopy. Derivative spectroscopy was combined with band cur ve-fitting procedures to quantitate the spectral information from the amide I' band. Nine component bands were found under the broad amide I ' band which reflect the presence of various substructures. The second ary structure is estimated to be 23% alpha-helix, 30% beta-sheets, 5% turns, 29% unordered and 13% beta-strand or extended, not forming beta -sheets, in contact with the lipid moiety. Comparison of the VLDL spec trum with that of its lipid fraction, together with H-D exchange measu rements, reveal strong protein-lipid interaction in agreement with pro teolysis studies.