Antibodies specific to deoxyguanosine 5'-phosphate

Binding of deoxyadenylate and deoxycytidylate antibodies to double-stranded DNA

Antibodies raised against deoxyadenylate and deoxycytidylate were found to react with double stranded DNA as assessed by highly sensitive avidin-biotin microELISA. The binding was specific as it was completely inhibited by the homologous hapten. The antibodies did not react with tRNA and rRNA. These antibodies were also shown to react with supercoiled and relaxed forms of pBR322 DNA as demonstrated by gel retardation assay.

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.

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.

Fluorescent nucleotides: application in a fluorescence immune assay

A fluorescence immune assay designed to measure anti-nucleotide antibody activity is described based on the synthesis of a fluorescent nucleotide probe possessing a low fluorescence quantum yield when free in aqueous solution (neutral pH). The fluorophore, AmNS (1-naphthylamine-5-sulfonic acid), was covalently conjugated to various phosphate derivatives of nucleotides through carbodiimide activation to form the fluorescent probe. The quantum yield (phi) of the fluorescent nucleotide in solution (neutral pH) was approximately 0.025 based on an excitation maximum of 320 nm and an emission maximum of 460 nm. Anti-nucleotide antibodies elicited in rabbits and mice served as standard immunological reagents in development of the fluorescence assay. Upon binding of an AmNS-nucleotide conjugate with homologous anti-nucleotide antibodies, the fluorescence quantum yield of the conjugate was significantly enhanced (12-35 x). Fluorescence enhancement was not obtained upon incubation of the fluorescent probe with normal Ig, non-immune rabbit sera and murine ascites fluid, or bovine and rabbit serum albumin. Nucleotide inhibition reactions were quantitatively measured in the fluorescence assay. Nucleotide binding results obtained with the fluorescence assay were correlated with a modified radioimmune Farr assay.