| Abstract: | A technique has been developed for placing site-specific crosslinks into DNA by using a psoralen derivative containing a sulfhydryl group. Plasmid pBR322 was nicked at the unique BamHI restriction site, and mercurated pyrimidines were introduced by nick-translation. Then the psoralen was specifically directed to this site in the dark through a Hg-S linkage prior to irradiation to form a crosslink. The location of interstrand cross-links was examined by electron microscopy of Pst I-cut molecules and found to be at or near the BamHI site. |
