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Phosphate membrane vesicle

Most results on calcium transport have been obtained using cytoplasmic membrane vesicles, which may be prepared in inside-out or right-side-out configurations. Inside-out vesicles may be obtained by the disruption of E. coli cells in a French press. These then accumulate Ca2+ in an energy-dependent fashion, provided ATP or an oxidizable substrate is available. Addition of phosphate enhances the uptake of calcium as calcium phosphate is precipitated inside the tell, thus accounting for the lack of exchangeability of the calcium.186... [Pg.570]

After preincubation of the brush border membrane vesicle preparation for 2 h, [2 14 C]urate uptake is initiated by adding 200 pi of incubation medium to 20 pi of the membrane suspension. The incubation medium has the following composition (mmol/1) 150 mannitol, 2 MgS04, 50 potassium phosphate buffer, pH 6.0 or 7.5, 0.02 [2-14 C]urate, and various concentrations of the inhibitor. At 10 s after the addition of the incubation medium, 200 pi portions of the suspension are pipetted onto the center of prewetted cellulose acetate filters kept under suction. The vesicles retaining on the filter are washed immediately with 5 ml of an ice-cold solution containing 150 mmol/1 mannitol and 50 mmol/1 potassium phosphate buffer, pH 6.0 or 7.5, which is used at the same pH as the incubation medium. Preincubations and incubations are performed at 23 1 °C. Each experiment is performed in triplicate. Corrections are made for the radioactivity bound to the filters in the absence of membrane vesicles. The term of the OH gradient-dependent urate uptake is defined as the difference between the uptakes in the incubation medium at pH 6.0 and that at pH 7.5. The OII gradient-dependent urate uptake at 10 s is assumed to present an initial velocity. [Pg.98]

Figure 8-38. Inhibition of immune precipitation of I-labeled t>-lactate dehydrogenase by increasing amounts of unlabeled purified D-lactate dehydrogenase (O), a 0,1% Triton X-100 extract of wild type membrane vesicles ( ), a 0.1% Triton X-100 extract of mutant membrane vesicles ( ), and 0.1% Triton X-100 in 0.1 Af potassium phosphate buffer, pH 7.1 (A). The 0.1% Triton X-100 extracts of wild type and mutant vesicles contained the same amounts of protein. The inhibitory effect of the wild type extract was compared with that of a purified i>lactate dehydrogenase preparation containing the same number of units of enzyme activity. [From S. Short and H. R. Kaback, J. Biol. Chent. 250 4285 (1975).]... Figure 8-38. Inhibition of immune precipitation of I-labeled t>-lactate dehydrogenase by increasing amounts of unlabeled purified D-lactate dehydrogenase (O), a 0,1% Triton X-100 extract of wild type membrane vesicles ( ), a 0.1% Triton X-100 extract of mutant membrane vesicles ( ), and 0.1% Triton X-100 in 0.1 Af potassium phosphate buffer, pH 7.1 (A). The 0.1% Triton X-100 extracts of wild type and mutant vesicles contained the same amounts of protein. The inhibitory effect of the wild type extract was compared with that of a purified i>lactate dehydrogenase preparation containing the same number of units of enzyme activity. [From S. Short and H. R. Kaback, J. Biol. Chent. 250 4285 (1975).]...
Foscarnet competitively inhibits Na -Pj cotransport in animal and human kidney proximal tubule brush border membrane vesicles, reversibly inhibiting sodium-dependent phosphate transport [48, 49]. Renal cortical Na-K-ATPase and alkaline phosphatase activity are not inhibited by foscarnet, nor is proline, glucose, succinate, or Na" transport [48,49]. Foscarnet induces isolated phosphaturia without hypophosphatemia in thyroparathyroidectomized rats maintained on a low phosphorus diet, without affecting glomerular filtration rate, urinary adenosine 3 5 -cyclic monophosphate (cAMP) activity, or urinary calcium, sodium or potassium excretion [48,50]. Sodium-Pj cotransport in brush border membrane vesicles from human renal cortex was reported to be even more sensitive to inhibition by foscarnet than in rat renal brush border membrane vesicles [49]. [Pg.386]

It makes possible a selective concentration of lipophiles in the membranes. Vesicles made of n-acyl lipids or of polyprenyl phosphates extract selectively into the membrane any lipophilic substance lipophilic pigments (Nile Red), cholesterol, polyprenols, carotenoids, etc. This is particularly important for those lipophilic substances that play a role in stabilizing the membrane cholesterol, hopanoids, polyprenols, and carotenoids (Bisseret et al., 1983 Milon et al., 1986 Lazrak et uZ.,1988 Krajewski-Bertrand et al., 1990). [Pg.432]

An extraordinary way of stabilizing RUO2-coated CdS colloids for H2 generation was chosen by Fendler and co-workers The colloidal particles were generated in situ in surfactant vesicles of dioctadecyldimethylammonium chloride and dihexa-decyl phosphate. Thiophenol as a membrane permeable electron donor acted as a sacrificial additive. Later, a surface active re-usable electron donor (n-C,gH3,)2N — (CHj)—CH2—CHj—SH, Br was incorporated into the vesicles. Its R—SS—R oxidation product could be chemically reduced by NaBH to regenerate the active electron donor. The H2 yields in these systems were only 0.5 %. However, yields up to 10% were later reported for a system in which CdS was incorporated into a polymerizable styrene moiety, (n-C,jH3jC02(CH2)2) N (CH3) (CH2CgH4CH=CH2>, CP, and benzyl alcohol was used as the electron donor. [Pg.136]


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See also in sourсe #XX -- [ Pg.40 , Pg.197 , Pg.200 , Pg.201 , Pg.202 ]




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