Angle resolved depolarised resonance Raman studies of beta-carotene in lipid/water mixtures.

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.

Fluorescence excitation profiles of beta-carotene in solution and in lipid/water mixtures.

Intrinsic fluorescence from all-trans beta-carotene molecules in solution and embedded in lipid/water mixtures has been observed under laser excitation and its excitation profiles measured. The profiles closely correspond to the absorption spectra. The observations can be explained in terms of a low-lying 1Ag excited state.

Particle aggregation in photosynthetic membranes of the blue-green alga Anacystis nidulans.

Freeze-fracture electron microscopy demonstrates that in photosynthetic membranes of the blue-green alga Anacystis nidulans quenched from a temperature below growth temperature, areas devoid of membrane particles occur. We suggest that this phenomenon is related to phase transitions in the photosynthetic membrane.

Intramembranous particles and chlorophyll complexes in chloroplasts.

The size and population density of large and small particles from freeze-fractured chloroplasts of three wild-type algae and of normal spinach were determined. Computer analyses of low-temperature absorption spectra of chloroplast preparations from these species were performed, and a possible correlation between the occurrence of seven chlorophyll complexes and the aforementioned properties of the intramembranous particles was studies. It was found that only single-sized particles occur in a species containing neither chlorophyll b nor chlorophyll a-685 complexes. The three remaining species carry particles of two sizes, termed large and small particles. However, from quantitative considerations it is concluded that the chlorophyll content of none of the various pigment complexes is related to the size and the population density of the studied particles. If such a relationship exists, it seems likely to be due to the carrier moiety of the chorophyll b-chlorophyll a-685 complex.