No abstract

The hypocrellin B (HB) was used as a fluorescence quencher to study the basic physical charactcristics of HB in membrane systems, including the diffusion speed of quencher from aqueous phase into membrane phase, the partition coefficient (P) of quenchtr between membrane and water, and the fluorescence quenching constant of protein (K(sv); K(q),). The experimental results show that the quenching of fluorescence in membrane protein by HB can be determined by the principle of dynamic quenching. The experimental process of fluorescence quenching was observed in detail by using the ESR technique. The signal of HB- was found to arise from an electron transfer from excited trytophan to HB.

Changes of sodium ionic concentration of human erythrocytes applied to pulsed electrical field (PEF) were studied by using shift reagent and NMR spectroscopy. The results show that the concentration of intraceUular Na(+) increases with the increasing intensity of PEF when the erythrocytes are applied to PEF with higher intensities. The relationship between intracellular Na(+) concentrations and the intensities of PEF does not follow linear or exponential behavior. As the intensities increase, the intracellular Na(+) concentrations increase even faster by an exponential curve. However under effects of PEF at lower intensities, intracellular Na(+) concentration decreases. Ouabain can inhibit the decrease of intracellular Na(+) concentration, and the inhibition increases with the increasing concentration of ouabain, suggesting that Na(+), K(+)-ATPase on cell membrane can be activated by PEF at lower intensities. Direct measurement of activities of the enzyme by using Malachite green method has confirmed this observation. Cell permeabilities to ions, activation of enzymes by electrical fields and transmission of physical signals like PEF across cell membranes are discussed.