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Results for “Countercurrent Distribution”

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At least 235 records · Page 13Linked to original sources
PubMed1978

[Method of partitioning polyene macrolide antibiotics].

Levorin and mycoheptin, polyenic antibiotics were separated into 3 and 7 heptaenic components respectively by the method of disc electrophoresis in 7.5 per cent polyacryl amide gel prepared with tris-HCl buffer, pH 8.9. It was shown that nystatin had different composition as dependent on the organism producing it. The results of electrophoresis confirmed the data of the counter-current distribution.

Antifungal Agents↗
PubMed1996

The formation of constants of mercury(II)--glutathione complexes.

The formation constants of the 1:1 and 1:2 complexes of Hg(II) with glutathione and their protonated species have been determined by using a competitive potentiometric titration with the competing ligand diethylenetriaminepentaacetic acid (DTPA). The formation constants of the 1:1 complex and its protonated species have not been reported previously. The formation constant of the 1:2 complex of Hg(II) and glutathione is substantially smaller than the accepted values that has been reported in the literature. These results have important implications in the models that have been employed to explain the mobilization and distribution of Hg(II) in biological systems.

Binding, Competitive↗
PubMed1984

Effect of sample dilution on measurements of free (unbound) hormones.

We describe the influence of sample dilution on the measurement of free or non-protein-bound hormones in serum or plasma. The concentration of free hormone in the sample will alter after dilution or addition of binding reagents. The extent of this equilibrium perturbation depends on the binding properties of the endogenous carrier proteins, which vary from sample to sample and from sample to reference standard. As examples, we demonstrate the different changes in concentrations of free thyroxin and free cortisol after dilution, both experimentally and by theoretical modeling of the hormone-protein distribution. We also show how this systematic error can be minimized in the design of free hormone assays.

Carrier Proteins↗
PubMed1992

Surface heterogeneity of rat sperm during maturation.

Rat sperm isolated from the caput and caudal epididymis and the vas deferens were subjected to multiple partition in aqueous two-phase systems. The technique was used to reveal heterogeneity of a sperm population with respect to particular surface properties. Sperm from all three regions gave broad distributions indicative of heterogeneous cell populations. Greatest heterogeneity was observed for cauda sperm with caput and vas sperm producing similar distributions. Following multiple partition sperm from different regions of the distribution profiles were immunostained with three antibodies known to recognise maturation antigens. The results show that some antigens are acquired during epididymal transit whilst others are present throughout. The partition (surface heterogeneity) seen cannot therefore be explained solely by the distribution of the antigens recognized by 2D6, 6B2 and 3D5.

Animals↗
PubMed1994

Effect of some poly(ethylene glycol)-bound and dextran-bound affinity ligands on the partition of synaptic membranes in aqueous two-phase systems.

Ligands with an apparent affinity for various structural elements on the surface of synaptic membrane fragments have been bound to the polymers poly(ethylene glycol) and dextran. The ligand-polymer derivatives have been included in aqueous two-phase systems composed of water, poly(ethylene glycol) and dextran. The uneven distribution of the polymers resulted in the concentration of the polymer-bound ligand in one of the two phases. The effect of the ligand-polymer on the partition of membranes was studied by using synaptic membranes from calf brain, obtained by standard centrifugation methods. By using ligand-containing two-phase systems for nine-step counter-current distribution of membranes, it was shown that the distribution behaviour of various parts of the membrane preparation could be affected. The distribution was followed by determination of opiate binding, acetylcholinesterase, and total membrane (using protein and light-scattering measurements).

Acetylcholinesterase↗
PubMed1984

Liquid-liquid extraction of membranes from calf brain using conventional and centrifugal counter-current distribution techniques.

Neural membranes isolated from calf brain have been partitioned in aqueous two-phase systems containing dextran and polyethyleneglycol. When the partition was repeated several times, using counter-current distribution technique, the distribution of the membranes between the upper phase and the interface changed in a non-ideal manner and in favour of the interface. By using a centrifugal counter-current distribution device the time for the experiment could be reduced by a factor of 7-8 and the distribution was similar to what could be expected for ideally behaving membranes. The time-dependent change of the membranes is discussed in terms of aggregation and lateral membrane perturbations. Despite this effect a certain fractionation has been achieved as deduced from analysis of cholesterol content, opiate receptor activity and acetylcholinesterase activity along the counter-current distribution row of fractions. Compared to the starting material these activities were enriched some two-fold in certain fractions.

Animals↗
PubMed1988

Lateral heterogeneity of rat liver plasma membranes analysed by counter-current distribution.

The lateral heterogeneity of rat liver plasma membranes was examined by fragmentation and fractionation by counter-current distribution in an aqueous two-phase polymer system. The distribution pattern was analysed by plotting the relative specific activities of marker components against each other. By this analysis asialo-orosomucoid receptors were found in a domain separated from domains containing 5'-nucleotidase and leucine aminopeptidase by another domain devoid of these markers. 5'Nucleotidase and leucine aminopeptidase resided in adjacent but separate domains. The experimental data were compared with corresponding plots of markers in model membranes. The model membranes yielded plots of different shapes depending on marker distribution and fragment size. This method of analysis should be useful for examining the lateral heterogeneity also of other membranes.

5'-Nucleotidase↗
PubMed1988

Partition and counter-current distribution of membrane particles in aqueous dextran-poly(ethylene glycol) two-phase systems with special reference to synaptosomes.

Aqueous two-phase systems composed of water, dextran and poly(ethylene glycol) can be used for the separation of biological particles. The adjustment of the partition of such particles between the two phases and the interface between them has been studied by using a preparation of synaptosomes (from calf brain cortex) also containing free mitochondria. The partition has been affected by variation of polymer concentrations and addition of salts, e.g. phosphates and chloride. The time for separation of the phases showed a bimodal behaviour with an initially rapid formation of bulk phases followed by a slow phase separation. The relative amount of mixed phases at the time of the transition was proportional to the amount of particles included. Counter-current distribution with moderate time for the phase separation was carried out in such way that the interface material travelled with approximately half the speed of the moving upper phase. In this way the distribution of the particles between the upper phase and the interface as well as between the interface and the lower phase could be studied in the same experiment. The heterogeneity of the synaptosome preparation was clearly demonstrated by counter-current distribution at low polymer concentrations while no separation was obtained when the system contained larger amounts of polymers. Possible reasons for this behaviour are discussed.

Animals↗