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At least 451 records · Page 25Linked to original sources
PubMed1989

Competitive protein binding assay for piritrexim.

A competitive protein binding assay for piritrexim (PTX, 1) that makes use of a commercially available radioassay kit for methotrexate has been developed. After it is selectively extracted from plasma, PTX competes with [125l]methotrexate for binding to dihydrofolate reductase isolated from Lactobacillus casei. Free drug is separated from bound drug by adsorption to dextran-coated charcoal. Piritrexim is measurable over a range of 0.01 to 10.0 micrograms/mL in plasma with a coefficient of variation less than 15%. The limit of sensitivity of the assay is approximately 2 ng/mL. An excellent correlation between this assay and a previously published HPLC method was found. published HPLC method was found.

Antineoplastic Agents↗
PubMedDate not supplied

[Diagnostic informative value of the method of competitive transcortin binding for determining corticosteroid levels in hypercorticism].

The level of nonmetabolized forms of the corticosteroids hydrocortisone and corticosterone in the blood and urine were determined in 3 groups of patients: with the Icenko-Cushing disease and syndrome and neuroendocrine form of the hypothalamic syndrome. The determination of the level of these hormones, a study of their circadian rhythm by the method of concurrent protein binding have shown that these indices are rather informative and can be recommended as diagnostic and differential criteria for the evaluation of the hypothalamo-hypophyseal-adrenal system.

17-Hydroxycorticosteroids↗
PubMed1978

Effect of storage on the apparent concentration of folate in erythrocytes, as measured by competitive protein binding radioassay.

The folate concentration in erythrocytes changes during incubation. Using whole blood samples and washed erythrocytes, I find greatly increasing concentrations of folate in washed samples at 37 degrees C, decreasing concentrations in whole-blood samples. This difference in behavior depends on a thermostable, ultrafiltrable factor in plasma. Exclusion of glucose or addition of fluoride did not affect these results. Decreasing concentrations of folate were found when iodoacetate or acetylphenylhydrazine was present. At 4 degrees C the concentrations of folate were stable for 72 h. I discuss possible explanations for the observed changes and their practical significance.

Binding, Competitive↗
PubMed1992

Effect of covalent modification on the binding of cholera toxin B subunit to ileal brush border surfaces.

A competitive binding assay has been developed to determine how modifications to the B subunit of cholera toxin affect the binding affinity of the subunit for an ileal brush border membrane surface. The Ricinus communis120 agglutinin (RCA120) specifically binds to terminal beta-D-galactosyl residues such as those found in oligosaccharide side chains of glycoproteins and ganglioside GM1. Conditions were designed to produce binding competition between the B subunit of cholera toxin and the RCA120 agglutinin. Displacement of RCA120 from brush border surfaces was proportional to the concentration of B subunit added. This assay was used to study the effect of modification of B subunit on competitive binding affinity for the ileal brush border surface. The B subunit of cholera toxin was modified by coupling an average of five sulfhydryl groups to each B subunit molecule and by reaction of the SH-modified B subunit with liposomes containing a surface maleimide group attached to phosphatidylethanolamine. SH-modified B subunit was approximately 200-fold more effective than native B subunit in displacing lectin from brush border surfaces in the competitive binding assay. The enhanced binding activity was retained on covalent attachment of the modified B subunit to the liposome surface. We conclude that the B subunit of cholera toxin may be a useful targeting agent for directing liposomes to cell surfaces that contain a ganglioside GM1 ligand.

Animals↗