Metals and DNA: molecular left-handed complements.

Chiral metal complexes provide unique molecular probes for DNA. Chiral reagents that "recognize" different local structures along the DNA strand have been designed by a process in which the asymmetry in shape and size of the complex is matched to that of the DNA helical groove. As a result, the chiral metal complexes provide very sensitive probes for local helical structure, both left- and right-handed. Direct coordination of chiral complexes to the DNA bases adds an element of sequence selectivity to the probe design. With a suitable reactive metal center, reagents that target chemically specific sites along the strand may be developed. One such chiral reagent, which cleaves left-handed DNA sites with photoactivation, has been useful in mapping this distinct conformation and examining its biological role. The conformation-specific molecular cleaver, much like a DNA-binding enzyme, recognizes and reacts at discrete sites along the DNA strand. These site-specific chiral metal complexes provide exciting new tools for probing the local variations in DNA structure and its role in the regulation of gene expression.