This award from the Inorganic, Bioinorganic and Organometallic Chemistry Program and the Biochemistry Program provides the third year of a three-year continuing grant to support the work of Dr. Jacqueline K. Barton of the California Institute of Technology. In collaboration with Dr. Lawrence A. Chasin of Columbia University, Dr. Barton will evaluate the usefulness of chiral metal complexes as probes of the secondary structure of DNA. Such metal complexes have proven useful in identifying segments of DNA with altered conformations, such as the so-called Z-DNA and cruciform DNA.