Specificity of deoxycytidylate antibodies

The RNA binding subset of adenosine antibodies

Hapten specific antibodies were elicited against adenosine-BSA conjugate (Ado-BSA) in rats. By radiohapten assay, two major populations of hapten specific antibodies were identified. They were directed against either adenosine trialcohol (Aox-red) or morpholino-adenosine (Morph-Ade). The association constant (Ka) for the 3H-Aox-red binding population was determined to be 1.02 X 10(7) M-1. Majority of the Aox-red specific antibodies were cross-reactive with Morph-Ade, but they did not cross-react at all with adenosine(A) or deoxyadenosine (dA). 3H-A binding subsets were actually Morph-Ade specific and constitute less than 10% of the hapten specific antibodies. The Ka value for the 3H-A binding was determined to be 4.5 X 10(6) M-1. A very minor and highly cross-reactive subset of Morph-Ade specific antibodies participate in RNA binding. Though a larger proportion of Morph-Ade specific antibodies interact with 3H-A, only a fraction of them bind to RNA. The extreme cross-reactivity and hence, the highly adaptive nature of the binding sites of the antibodies interacting with RNA, might be a stringent requirement for recognising adenine residues of nucleic acids in solution.

Mechanism of coupling periodate-oxidized nucleosides to proteins

This paper describes a mechanism of coupling periodate-oxidized nucleosides to proteins. Each of the dialdehyde groups of a periodate-oxidized nucleoside is shown to couple to lysine residues on different protein molecules through Schiff bases, thereby cross-linking different protein molecules, forming a polymer. This is in contrast to the previous model in which nucleosides were suggested to couple to proteins through a morpholine structure. The cross-linked structure of the nucleoside-antigen, significantly different when compared to the native protein, may affect the specificity and the efficiency of antibody production.

Characterization of adenosine-bovine serum albumin immunogen and its antibodies

Antibodies to adenosine were elicited in rabbits using a conjugate of adenosine (periodate oxidized) and bovine serum albumin as immunogen. The conjugate was found to be of a higher molecular size than the original protein, apparently due to the cross-linking of albumin molecules by the dialdehydes generated during the periodate oxidation of adenosine. It produced high titres of antibodies, which were 400-fold more reactive to adenosine-trialcohol than to adenosine, when measured by a nitrocellulose filter assay. In addition, a specific elution procedure for the isolation of hapten-specific antibodies is described.

Antibodies to guanylic acid: fractionation and specificities

Guanylic-acid-specific antibodies were elicited in rabbits, using as immunogen pG linked through 5'-phosphate to thyroglobulin. Specificity and affinity of antibodies to nucleotides, nucleosides, DNA, and RNA were studied by their binding to radioactive ligands and competition experiments. Guanylic-acid-specific antibodies do not bind to deoxyguanylic acid and have an average association constant of 10(7) M-1 at 4 degrees C. Binding of the antibodies to 3H-RNA is G-specific. The antibodies do not bind to 32P-ssDNA or 32P-dsDNA. The pG-specific antibodies could be separated into different fractions by affinity chromatography. These fractions, though specific to pG, differ in their cross-reactivities to nucleosides and nucleotides.

Base specific binding of deoxyguanylate and deoxycytidylate antibodies to double stranded DNA

Antibodies raised in rabbits against deoxyguanylate and deoxycytidylate bind to 3H-lambda double stranded DNA and the binding is base specific. The concentrations of antibody populations that bind to double stranded DNA are much less than those binding to denatured DNA. Due to their low concentrations, these antibodies were not detected in earlier studies. These antibodies are expected to be useful to probe the conformational flexibilities of double stranded DNAs.