Competitive protein binding assay for methotrexate.

Competitive protein-binding assay for 25-hydroxycholecalciferol.

1. A competitive protein-binding assay for plasma 25-hydroxycholecalciferol was developed, using Sephadex LH-20 columns for the isolation of the sterol and a partially purified protein from rat serum as the binding protein. 2. The mean plasma 25-hydroxycholecalciferol in eighteen male and female normal volunteers was 38 5 SD 14 pmol/ml (1 5.2 & 5.6 nglml). 3. Levels of 25-hydroxycholecalciferol...

Trimethoprim interferes with serum methotrexate assay by the competitive protein binding technique.

Administration of Bactrim (a combination of trimethoprim and sulfamethoxazole) to a patient who also was receiving methotrexate caused a significant increase in apparent plasma methotrexate concentrations as determined by competitive protein binding assay with use of dihydrofolate reductase (EC 1.5.1.3) from Lactobacillus casei as the binding protein. This spurious increase was caused by trimet...

Rapid, specific assay for plasma cortisol by competitive protein binding.

We describe a modified competitive protein-binding method for assay of plasma cortisol. Plasma samples are deproteinized by dilution with an ethanol/phosphate buffer, followed by heating at 100 degrees C for 2 min. Horse serum is used as the source of transcortin. Free radioactivity is separated from the protein-bound component by partition into liquid scintillation counting within 60 min. The ...

A Competitive-Binding Assay forGlycopeptideAntibioticsof the VancomycinClass

A solid-phase enzyme-receptor assay (sPcR.A) has been developed for glycopeptide antibiotics of the vancomycin class such as teicoplanin, vancomycin, ristocetin, avoparcin, actaplanin,A-47934, A-41 030, and A-3551 2-B. The assay exploitsthe mechanismof most action of these antibiotics, which is based on their interaction with acyl-D-alanyl-Dalanine, a constituentof the walls of mostgrowingbacte...

Enzyme-Linked Immunosorbent Assay Competitive Binding Inhibition