APPLICATION OF FOURIER-TRANSFORM RAMAN-SPECTROSCOPY TO BIOMEMBRANES -1064-NM EXCITED RAMAN-SPECTRA OF HOG KIDNEY MITOCHONDRIAL OUTER MEMBRANES

Fourier transform Raman spectra with 1064 nm excitation were measured at ambient temperature on hog kidney mitochondrial outer membrane prep arations of ultracentrifuged pellet and almost fluorescence-free Raman spectra with satisfactory signal-to-noise ratios were obtained. Fouri er transform IR spectra were also measured. The observed Raman and inf rared wavenumbers were tentatively assigned to membrane proteins and p hospholipids, respectively. CH stretching, phospholipid CC stretching and PO2- stretching vibrations are discussed. To examine the applicabi lity of near-infrared excited Fourier transform Raman spectroscopy to the study of the inhibitory effects of inorganic ions on membrane-boun d monoamine oxidase activity, measurements were also made on membrane preparations suspended in phosphate buffer (pH 7.0) at ambient tempera ture in the absence (control) and presence of NaCl, and studies were m ade of phospholipid CC stretching and PO2- stretching vibrations, whic h are relatively unaffected by H2O self-absorption by near-infrared ra diation. It was found that the presence of NaCl decreased the intensit y of the 1080 cm(-1) gauche form acyl chain CC stretching Raman band r elative to those of the all-trans CC stretching Raman band at 1126 and 1068 cm(-1). This result was different from that obtained with aqueou s dispersions of phosphatidylcholine (PC), for which it has been repor ted previously that monovalent ions such as Na+ do not affect the I-tr ans/I-gauche ratio.