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Raman spectra of n-hexadecynoic fatty acids, CH3(CH2)m-2C ~-C(CH2),_2COOH (with n = 4, 6, 7, 8 and 12, m + n = 16) and their potassium salts were recorded and assigned. The skeletal optical mode (SOM) regions were analysed on using the dispersion curve of the ~'4 (stretch) vibrations of saturated fatty acids. The Iocalised vibrations of the carboxyl-and methyl-terminated sections of the hydrocarbon chains were assigned to the phase ditierences 8 = kzr/m and k~r/n (k = 1, 2 .... ), respectively. Evidence for a ~'4 vibration with 6 = ~r/2m was found. The materials were found to be resistant to chemical decomposition under laser illumination.

The orientational ordering of beta-carotene incorporated in lamellar model membranes above their main phase transitions has been studied by angle resolved depolarised Resonance Raman scattering. The ordering strongly depends on the chemical composition of the lipid bilayers: in di-oleoyl lecithin (DOPC) the carotenoid molecules lie parallel to the bilayer plane, while in di-galactosyl diglyceride (DGDG) a bimodal distribution was found with molecules lying both parallel and perpendicular to the membrane phase. We have therefore studied the orientational statistics of beta-carotene molecules embedded in macroscopically ordered lipid bilayers by Resonance Raman techniques [8]. The temperature of the samples was well above the phase ~To whom correspondence should be addressed.

Derivative StokesRaman spectroscopy has been applied to biomembrane systems containing the fluorescent antibiotic amphotericin B. The membranes studied included weakly scattering solutions of dimyristoylphosphatidylcholine (DMPC) and multilamellar liposomes composed of DMPC and cholesterol. In this techqnique, the wavelength of an Ar ion-laser pumped, tunable CW Rhodamine 66 dye laser was sinusoidally modulated with an electro-optic buefringent tuner. The wavelength-modulated Raman signal becomes amplitude-modulated at the exit slit of a scanning monochromator. The signal, demodulated by a phase-sensitive detector, was proportional to the first derivative of the Raman spectrum under appropriate conditions. The results indicate that this modulation technique can offer improvements in Raman signal-to-noise ratios of up to a factor of two for the conformationally sensitive phospholipid acyl-chain vibrations of the biomembranes.