[Gene diagnosis with an affinity sensor, BIACORE--principle and applications].

We are developing new techniques for detecting point mutations by DNA-DNA hybridization and DNA-protein interaction analysis with an affinity sensor, BIACORE. To detect point mutations by the hybridization method using synthetic oligonucleotides, we already found that the length of the probe and the location of mismatches were important. The PCR products of the N-ras gene derived from Hep G2 cells, which have heterozygous point mutations at codon 61 in the gene, were analyzed and the point mutations were detected with 13-mer probes. We suggest that the detection method using DNA-DNA hybridization is useful for detecting known point mutations. However, detect unknown mutations, E. coli mismatch recognition protein, MutS, was employed. All mismatches in immobilized 20 base pairs of double-strand DNA could be detected by MutS binding. We have started to apply of the MutS to the detection of point mutations in PCR products.