Wang 9808298 Ultra-high resolution DNA structures This study is aimed at producing ultra-high resolution (< 0.8 ) DNA structures using advanced cryo-crystallography. It is designed to provide reliable geometric (bond length and bond angle) and motional information about DNA molecules in different conformational contexts. These highly reliable new structures will be the basis for constructing better DNA force-field parameters which will benefit the structural refinement of DNA, protein-DNA complexes, and ligand-DNA complexes. Until recently, the structure determination of biological macromolecules was usually carried out at medium, e.g., 2 , resolution. Such an analysis would involve restrained least square refinement which depends on a reliable set of target geometric values of the building blocks (amino acids and nucleotides). An improvement on the reliability of the geometric (bond length and bond angle) information of DNA molecules in different conformational contexts is desired. Crystals to be studied in this study thus include: 1. B-DNA: The DNA decamer of CCAGGCCTGG and its variants, 2. A-DNA: The DNA decamer of AGGGGCCCCT and its variants, and RNA.DNA chimera r (GC)d(GTATACGC), 3. Z-DNA: The Z-DNA structures of CGCGCG, m5CGTAm5CG and CGCGTG, and 4. Intercalator-DNA complexes: the formaldehyde-crosslinked daunorubicin/doxorubicin-CGCGCG adducts. They diffract x-rays to atomic resolution (better than 1 ) on a R-Axis II system under cryo conditions. Higher resolution data will be collected on a R-AxisIIc image plate system or a Siemens CCD system using MoKa radiation (wavelength 0.7107 ). Ultra-high resolution data (better than 0.7 ) will be collected on synchrotron sources, and structures refined by individual atomic anisotropic refinement using SHELX97. The electronic properties will be analyzed by the program suite of XD. All results will be made available to the public with the deposition of coordinates, structure factors and calculated force-fields to both Nucleic Acid Databa se and Brookhaven Protein Databank at the time of publication for immediate release. 2. Non-technical DNA plays a central role in life. Understanding the structures of DNA is important for understanding its functions. The interactions between DNA and various biologically-relevant molecules can be analyzed by x-ray crystallography. This research project is aimed at producing DNA structures at ultra-high resolution using advanced crystallographic methods, including the collection of x-ray diffraction data at-150 degrees C and the use of powerful synchrotron x-ray sources. This work will provide highly reliable geometric and motional information about DNA molecules. This new information will form the basis for structural refinement of DNA, protein-DNA complexes, and ligand-DNA complexes.
