A complex of single-strand binding protein and M13 DNA as hybridization probe

Single-stranded DNA was complexed to the single-strand binding protein (SSB) of Escherichia coli in a mass ratio of 30:1. The protein moiety of this complex can be labelled by a number of methods of which we have chosen radio-iodination and biotinylation as examples. The SSB-M13 DNA complexes, labelled to high specific activities, were used as probes in hybridization experiments in which 1.6 X 10(-18) moles of immobilized target DNA were detected. The stability of the hybrids was not severely decreased by the binding of SSB. Analysis of hybrids by electron microscopy showed that complexing of DNA with SSB could be used to allow its subsequent identification in the hybrids.