Preparation of oligodeoxynucleotide-alkaline phosphatase conjugates and their use as hybridization probes.

Short synthetic oligonucleotides have been covalently cross-linked to alkaline phosphatase using the homobifunctional reagent disuccinimidyl suberate. The oligomers, twenty-one to twenty-six bases in length, are complementary to unique sequences found in herpes simplex virus, hepatitis B virus, Campylobacter jejuni and enterotoxigenic Escherichia coli. Each oligomer contains a single modified base with a 12-atom "linker arm" terminating in a reactive primary amine. Cross-linking through this amine results in oligomer-enzyme conjugates composed of one oligomer per enzyme molecule that have full alkaline phosphatase activity and can hybridize to target DNA fixed to nitrocellulose within 15 minutes. The hybrids are detected directly with a dye precipitation assay at a sensitivity of 10(6) molecules (2 X 10(-18) mol) of target DNA in 4 hours development time. The enzyme has no apparent effect on selectivity or kinetics of oligonucleotide hybridization and the conjugates can be hybridized and melted off in a conventional manner.