CHANGES IN ELASTIN IN HUMAN ATHEROSCLEROTIC AORTA - C-13 MAGIC-ANGLE SAMPLE-SPINNING NMR-STUDIES

The dipolar-decoupled, natural abundance Fourier transform and cross polarization [C-13] NMR spectra of human elastin isolated from atherosclerotic aorta and aortas free of atherosclerotic lesions, bovine insoluble elastin and bovine kappa-elastin were obtained at 75 MHz, with 5-7 kHz magic angle sample spinning. Spin-lattice rotating frame relaxation parameters were measured for protons (T1 rhoH) and for carbons (T1 rhoC) at room temperature. Proton relaxation times were shorter for bovine kappa-elastin (T1 rhoH = 1.7 ms) than for bovine elastin (T1 rhoH) = 3.5 ms). Calculation of T1 rhoH showed no differences between human normal and atherosclerotic elastins. T1 rhoC were shorter for bovine kappa-elastin than for bovine elastin. While alpha-carbons of human atherosclerotic elastin had shorter T1 rhoC than normal elastin alpha carbons, carbons from hydrophobic amino acid side chains had longer T1 rho C for atherosclerotic then for normal elastin. Biochemical studies of aortic wall and purified elastin showed significantly increased content of lipids (atherosclerotic 67.7 mmol/g elastin, control 54.7 mmol/g elastin) and calcium (atherosclerotic 38.3 mmol/g elastin, control 19.6 mmol/g elastin). Changes in relaxation parameter values may be caused by the structural and biochemical changes in human elastin. Increased mobility of polypeptide chains as based on the model kappa-elastin studies is caused by the action of elastase. Restriction of mobility is expected to be caused by the accumulation of lipids and calcium.