Activation of phospholipase C and phospholipase D by stimulation of adenosine A1, bradykinin or P2U receptors does not correlate well with protein kinase C activation

Gradient-enhanced, two-dimensional, homonuclear correlation techniques (GCOSY) of carbohydrates provide numerous correlations based on 4J and 5J long-range interactions. Intraresidue correlations, involving all 1H resonances of a given pyranose ring with its anomeric proton, are consistently observed in alpha-pyranosyl residues at approximately 5 to 10 times lower intensities than vicinal 3J correlation cross peaks. beta-Anomers, pyranosyl residues with axial H1 protons, show very few such effects. Both alpha and beta anomers do, however, exhibit interresidue 4J correlations across the glycosidic linkage as shown for several linear and branched oligosaccharides ranging from three to five residues and are especially useful for spectral assignments in the envelope of pyranosyl ring protons located in the typically very crowded 3 to 4 ppm region. These effects depend on the strength and duration of the applied gradients.     

Molecular topology of the photosynthetic light-harvesting pigment complex, peridinin-chlorophyll a-protein, from marine dinoflagellates

The photosynthetic light-harvesting complex, peridinin-chlorophyll a-protein, was isolated from several marine dinoflagellates including Glenodinium sp. by Sephadex and ion-exchange chromatography. The carotenoid (peridinin)-chlorophyll a ratio in the complex is estimated to be 4:1. The fluorescence excitation spectrum of the complex indicates that energy absorbed by the carotenoid is transferred to the chlorophyll a molecule with 100% efficiency. Fluorescence lifetime measurements indicate that the energy transfer is much faster than fluorescence emission from chlorophyll a. The four peridinin molecules within the complex appear to form two allowed exciton bands which split the main absorption band of the carotenoid into two circular dichronic bands (with negative ellipticity band at 538 nm and positive band at 463 nm in the case of peridinin-chlorophyl a-protein complex from Glenodinium sp.). The fluorescence polarization of chlorophyll a in the complex at 200 K is about 0.1 in both circular dichroic excitation bands of the carotenoid chromophore. From these circular dichroic and fluorescence polarization data, a possible molecular arrangement of the four peridinin and chlorophyll molecules has been deduced for the complex. The structure of the complex deduced is also consistent with the magnitude of the exciton spliting (ca. greater than 3000 cm-1) at the intermolecular distance in the dimer pair of peridinin (ca. 12 A). This structural feature accounts for the efficient light-harvesting process of dinoflagellates as the exciton interaction lengthens the lifetime of peridinin (radiative) and the complex topology increases the energy transfer probability. The complex is, therefore, a useful molecular model for elucidating the mechanism and efficiency of solar energy conversion in vivo as well as in vitro.