Abstract:In order to further characterize the active site of fetal lamb 3β, 20α-Hydroxysteroid Oxidoreductase, we have synthesized the radioactive 16α-bromoacetoxyprogesterone and 5α-dihydrotestosterone 17-bromoacetate as affinity labeling reagents. Both of them are the irreversible, active-site-directed and competitive inhibitors of the enzyme. When the concentration of the enzyme is 1 μmol/L, inhibitor is 100 μmol/L, the inactivation reaction followed pseudo-first-order kinetics with a t_0.5=75 min (16α-BAP) and t_0.5=480min (5α-DTB). When substrate progesterone or 5α-dihydrotestosterone was present in the incubation mixture, the speed of inactivation of the enzyme was slowed down. The labeled enzyme was hydrolyzed by hydrochloric acid, through amino acid analysis, the labeled histidine was identified. The histidine at active site may play important role in the oxidoreductive reaction.

Abstract:Motivated by our earlier demonstration that calmodulin (CaM) antagonist-trifluoperazine (TFP) effectively inhibits cell proli feration and DNA synthesis in human stomach carcinoma MGC-803 cells with simultaneous induction of normalized cell morphology, this work was designed to investigate the mechanisms of TFP effect on MGC-803 cells By using biochemical assays, CaM and phosphodiesterase(PDE) activities in TFP treated MGC-803 cells were quantitatively analyzed with comparison to untreated control cells. TFP treated mouse ascitic hepatoma cells were analyzed as parallel. Results indicate that TFP selectively inhibits Ca²⁺/CaM-dependent PDE activity rather than the PDE-binding activity of CaM in drug-treated cells of both types. However, both MGC-803 and mouse hepatoma cells exposed: to aminophylline (2mmol/L) for 3 days or shorter time showed decrease in PDE-binding activity of CaM. The possible mechanisms concerning TFP effects and their role in regulating cell proliferation of MGC-803 cells were discussed.

Abstract:This treatise introduces the results of the auther's research in using the method of SAXS (the small angle X-ray scattering) on the structure of the liquid-crystal system made from micro-hydro cephalin with water, methanol and ethanol respectively. Experiments reveal to us the following phenomena: in the cephalin-water system when the content of water increases, the repeat distance of bilayers in the liquid-crystal system of cephalin and water widens and in the cephalin-methanol and cephalin-ethanol system, when the content of alcohol increases the repeat distance narrows; according to the multiplies of hydro-carbon chain in alcohol, the repeat distance varies from wider to narrower, then vanishes gradually and at last the liquid-crystal phase changes into liquid phase. Therefore it is quite clear that water and alcohol exert different influence on the repeat distance of liquid-crystal phase of cephalin.