Protein binding of 3',5'-adenosine cyclic monophosphate acid

Abstract

It is described the adaptation of a protein binding method for cAMP determination using charcoal for separation of bound/free nucleotide. The effect of cyclic receptor protein (CRP) dilution, concentration of charcoal, incubation time and crossreactivities with different nucleotides were studied. It was found a high precision in measurements of replicates of identical samples with a lower detection limit of 0.12 pmol/tube and excellent yield in recovery studies (100 ± 6.9 SD). Also the specificity was rather high as proved by only moderate displacement of H’-cAMP-CRP binding by dybutiryl cAMP and cGMP at very high concentrations of these nucleotides. The results in normal urine (1.950 ± 1.106 SD nmol/ml) and plasma (11.2 ± 4.2 SD pmol/ml) samples are in agree­ ment with most of the reported in the literature.