Linear and supercoiled DNA were cleaved by HPLC purified seryl-histidine di
peptide(SH). It was found that the DNA fragments produced by the reaction o
f SH and DNA could be ligated together by T-4 DNA ligase. This result impli
ed that the SH was the first example of the ion-free artificial DNA cleavag
e agent that could split DNA by hydrolysis mechanism.