Antibody binding characteristics of geometrical isomers of testosterone 3-(O-carboxymethyl)oxime.
Geometrical isomers of testosterone 3-(O-carboxymethyl)oxime and their histamine derivatives were purified on reverse-phase high pressure liquid chromatography, and their antibody binding characteristics were studied. Using a competitive testosterone enzyme immunoassay, the unfractionated mixture of the oximes showed 75% cross-reactivity with respect to testosterone, whereas the isolated 3Z- and 3E-isomers showed 124% and 26% cross-reactivity, respectively. The cross-reactivity was increased in the histamine derivatives, but the difference in cross-reactivity of the two isomers was reduced. Suppression of the ionization of the carboxyl group by lowering the pH of the incubation mixture in the antigen-antibody binding step raised the cross-reactivity of the mixture of free oximes to 128%, at pH 4.0. Thus, the geometry and ionization state of the carboxymethyl oxime group has a profound effect on the affinity of the isomers for the antibody.
Indian Institute of Chemical Biology, Calcutta.
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D000818:Animals; D000906:Antibodies / Q000276:immunology*; D003429:Cross Reactions; D007124:Immunoenzyme Techniques; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy; D010091:Oximes / Q000737:chemistry / Q000276:immunology*; D011374:Progesterone / Q000276:immunology; D011817:Rabbits; D013739:Testosterone / Q000031:analogs & derivatives* / Q000737:chemistry / Q000276:immunology
D000906:Antibodies; D010091:Oximes; C121237:testosterone 3-(O-carboxymethyl)oxime; D013739:Testosterone; D011374:Progesterone