Article

Fluidity of the microsomal membrane and cytochrome P450 reduction kinetics of pig liver microsomes as a consequence of organic solvent impact

Biophysical Department, University of Bremen, Germany.
Xenobiotica (Impact Factor: 2.1). 02/1993; 23(1):71-8. DOI: 10.3109/00498259309059363
Source: PubMed

ABSTRACT 1. The effect of the aromatic solvents toluene, xylene and ethylbenzene on microsomal membrane fluidity and anaerobic NADPH-reduction kinetics were studied. 2. The relation of membrane fluidity to the kinetics of cytochrome P450 reduction by NADPH-cytochrome P450 reductase was examined with regard to a membrane-mediated molecular organization of the multienzyme components of the monooxygenase system. 3. Membrane fluidity changes were detected with the steady-state pyrene excimer formation method and with fluorescence lifetime measurements after incubation of the microsomes with organic solvents. 4. Increase in membrane fluidity in presence of organic solvents leads to a small but significant decrease of the rate constant of the cytochrome P450 reduction kinetics and a change in the relative amplitudes of the components of the biphasic response. 5. The results support the idea of a molecular organization of cytochrome P450 in clusters. Fluidization of the microsomal membrane by organic solvents increase the cytochrome P450 cluster formation.

0 Followers
 · 
61 Views
  • Source
  • [Show abstract] [Hide abstract]
    ABSTRACT: The authors describe a decoding scheme and erase sequence for a 5-V-only sector-erasable flash memory. A source line decoder eliminates the erase disturb problem and lowers the power consumption. The maximum switching voltage is reduced to 10 V, which makes possible a tight word line pitch for a 64-Mb flash memory. Narrow threshold voltage distribution of erased memory cells is obtained by programming after erase
    VLSI Circuits, 1992. Digest of Technical Papers., 1992 Symposium on; 07/1992
  • [Show abstract] [Hide abstract]
    ABSTRACT: A brief literature review shows that ionizing radiation in biological membranes and in pure lipid membranes causes malondialdehyde formation, indicating lipid peroxidation processes. With respect to membrane fluidization by ionizing radiation, in pure lipid membranes rigidization effects are always reported, whereas contradictory results exist for biological membranes. Starting from the assumption that membrane proteins at least partly compensate for radiation effects leading to a rigidization of membrane lipid regions, pig liver microsomes, as a representative protein-rich intracellular membrane system, were irradiated with X-rays or UV-C with doses up to 120 Gy at a dose rate of 0.67 Gy min-1 and up to 0.73 J cm-2 at an exposure rate of 16.2 mJ cm-2 min-1, respectively. For both irradiation types a weak but significant positive correlation between malondialdehyde formation and membrane fluidity is revealed throughout the applied dose ranges. We conclude that the membraneous protein lipid interface increases its fluidity under radiation conditions. Also, thymocyte ghosts showed an increased fluidity after X-ray irradiation. Fluidity measurements were performed by the pyrene excimer method.
    Biophysik 02/1994; 33(4):303-13. DOI:10.1007/BF01210452 · 1.58 Impact Factor
Show more