A novel 24 residue peptide, Ile-Arg-Met-Lys-Ile-Gly-Val-Met-Phe-Gly-Asn-Pro-Glu-Thr-Thr-Thr-Gly-Gly-Asn-Ala-Leu-Lys-Phe-Tyr, derived from RecA protein can discriminate a single-stranded DNA (ssDNA) from a double-stranded DNA (dsDNA) and a new developed support with this peptide recognizes ssDNA but not dsDNA.