15-cis-beta-carotene found in the reaction center of spinach photosystem II.

Solvent extraction at approximately 4 degrees C in complete darkness, and subsequent analysis by high-pressure liquid chromatography (at approximately 4 degrees C) using an apparatus equipped with a two-dimensional diode-array detector, spectroscopically identified 15-cis-beta-carotene in the reaction center (RC) of spinach photosystem II (PS II). The result revises a previous conclusion that beta-carotene bound to the PS II RC takes the all-trans configuration [Fujiwara, H., Hayashi, H., Tasumi, M., Kanaji, M., Koyama, Y. and Satoh, K. (1987) Chem. Lett. 2005-2008], and generalizes the concept established for purple photosynthetic bacteria that 15-cis-carotenoid is naturally selected by the photosynthetic reaction centers.

Temperature-induced spectral properties of chlorophyll a incorporated into egg-yolk lecithin liposomes and lipo-protein complexes.

The temperature-induced fluorescence changes of Chl a in the systems consisting of albumin-egg-yolk lecithin and only lecithin were studied. As plotted against temperature in liposomes the fluorescence intensity of Chl a has a maximum at approximately 35 degrees C. In CLP complexes the curve profile for the fluorescence intensity versus temperature is sharper and the maximum occurred at a lower temperature (25 degrees C). No fluorescence maxima for ANS in liposomes and for Chl a in isotropic solutions were found. The second derivative absorption spectra of the investigated lipid systems exhibited bands which were characteristic of monomeric Chl a. We suggested that in the temperature zone studied Chl a in vitro is embedded within lipid bilayer rather than attached to the proteins. The occurrence of the fluorescence intensity maximum of Chl a in liposomes and lipo-protein complexes is related to the effects: temperature quenching of the fluorescence, Chl a-lipid interaction.

15-Cis-ß-carotene found in the reaction center of spinach Photosystem I.

ß-Carotene was extracted from spinach Photosystem I reaction centers (one consisting of the Psa A, B, C, D and E subunits and the other consisting of the Psa A and B subunits alone), and the extract was subjected to high-pressure liquid chromatography using an apparatus equipped with a two-dimensional diode-array detector; all the procedures were performed at ≈ 4 °C in complete darkness. Both 15-cis and all-trans-ß-carotene were identified in the extract by means of electronic absorption spectroscopy. Thus, universal presence of 15-cis carotenoid in the reaction centers of purple photosynthetic bacteria and of spinach Photosystem I and Photosystem II has been shown.

Excitation energy transfer between ß-carotene and chlorophyll-a in various systems.

The excitation energy transfer from ß-carotene to chlorophyll-a in several seminatural systems such as liposomes, lipid layers and PSI complex has been studied at room and liquid nitrogen temperature. Only in a case of PSI complex an efficient energy transfer (about 30%) from ß-carotene to chlorophyll-a has been observed. The results of energy transfer were discussed on the ground of Dexter's mechanism by taking into account the recently discovered energy level ((1)Ag) of ß-carotene.