QUANTITATIVE AND NONDESTRUCTIVE ANALYSES OF FATTY-ACID ESTERS AND CHOLESTEROL IN BRAIN-TISSUES BY FOURIER-TRANSFORM INFRARED-SPECTROSCOPY

Brain tissues obtained from rats were examined with Fourier transform infrared spectroscopy using a beam condenser apparatus to determine quantitatively and non-destructively the amount of fatty acid esters and cholesterol in the small specimens. For the analysis of fatty acid esters we calculated the ratio between the peak intensities of the fatty ester C = O (1730 cm-1) or methylene CH (2850 cm-1) stretches and amide II band (1550 cm-1), and compared it with the amount of fatty acid esters per mg protein determined chemically by a routine method. For analysis of cholesterol we measured the second derivative spectra between 1300 and 1400 cm-1 and the intensity of a band at 1366 cm-1 in the second derivative spectrum was compared with that of the amide II band in the normal absorption spectrum. This infrared analysis of cholesterol was compared and showed good correlations with the chemically defined data. These results suggest that the infrared technique can provide non-destructively quantitative data for the content of fatty acid esters and cholesterol in biological tissues.