We describe an immunoanalytical procedure for the detection and quantitation of 3-alkyladenines in biological samples with the use of anti-(3-alkyladenine) monoclonal antibodies (Mab). A new hapten-protein conjugate, 3-ethyl-8-(3-carboxypropyl)-adenine, was used for immunization of BALB/c mice after conjugation to carrier proteins via the carboxyl group. Eighty-nine hybridomas were established which secrete anti-(3-alkyladenine) Mab with antibody affinity constants ranging from 1 x 10(7) to 5 x 10(9) l/mol for 3-ethyladenine (3-EtAde). One of these Mab (EM-6-47) had detection limits of 30 fmol for 3-EtAde, 17 fmol for 3-n-butyladenine (3-BuAde) and 475 fmol for 3-methyladenine (3-MeAde) respectively, at 25% inhibition of tracer-antibody binding. The binding pattern of Mab EM-6-47 revealed high specificity for adenine substituted at N-3 with different alkyl residues and no, or very low, cross-reactivity with other alkylated or unmodified nucleic acid components or structurally related compounds. 3-MeAde and 3-EtAde can be well separated from nucleic acids, and from rat and human urine samples, using HPLC with two successive stationary phases. Using Mab EM-6-47 in conjunction with a competitive RIA, both 3-MeAde and 3-EtAde were detected in the range of 100-300 ng (3-MeAde) and 2-10 ng (3-EtAde) in urine samples (10 +/- 2 ml) of untreated rats collected over a 24 h period. Only 3-MeAde (range 1.3-24.20 micrograms) was found in human urine samples. The concentration of 3-EtAde in rat urine increased significantly during the 24 h following a single i.v. application of N-ethyl-N-nitrosourea. After i.p. application of known amounts of 3-MeAde and 3-EtAde, greater than 90% of 3-MeAde and greater than 70% of 3-EtAde were excreted in rat urine within the subsequent 24 h. The concentration of 3-alkyladenines in body fluids (urine) may thus provide a useful indicator of environmental exposure to nucleic acid-reactive agents, and the immunoanalytical procedure described here permits the sensitive determination of adenines carrying different substituents at N-3.
A new method for the covalent modification of polymers in a two-step process is described. Squaric acid diethylester reacts with primary or secondary aliphatic amines selectively to ester amides. It is shown for the first time that this class of compounds react with polymeric systems containing amine functionalities (e.g. ε-amino groups of proteins) in aqueous solution, forming stable squaric acid diamide linkages. Three different monoamides were synthesized and the reaction rates of diamide formation versus hydrolysis were determined. Detailed kinetic studies revealed that unwanted hydrolytic side-reactions are more than ten times slower than the formation of squaric acid diamides
This paper describes the enzyme-catalyzed in vitro synthesis of double-stranded DNA (ds-DNA) containing [3H]-labeled O(6)-ethylguanine (O(6)-EtGua), an alkylation product strongly implicated in mutagenesis and carcinogenesis by ethylating N-nitroso carcinogens. Single-stranded DNA (ss-DNA) containing O(6)ethyl-[8-3H]-2'-deoxyguanosine was synthesized using terminal deoxynucleotidyl transferase. The parameters determining yield of reaction, base ratios, and DNA chain length, were investigated. The O(6)-EtGua-containing ss-DNA could be replicated by DNA polymerase I, as indicated by the incorporation of [8,5'-3H]-2'-deoxyguanosine-5'-monophosphate and by the resistance of the replication product to nuclease S1 digestion. ds-DNA's with chain lengths between approximately 200 and 1000 base-pairs and O(6)-EtGua/guanine molar ratios of approximately 10(-2)--10(-3) were synthesized. Their use in the analysis of enzymatic mechanisms involved in the elimination of O(6)-alkylguanine from the DNA of mammalian cells is discussed. The procedure of synthesis described for (O(6)-EtGua)-containing ds-DNA may also be applicable for the production of ds-DNA containing structurally modified bases other than O(6)-EtGua.
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