This research is directed toward the goal of understanding the structural organization of genomic DNA and associated nuclear proteins through detailed 3-dimensional analysis of structures such as the nucleosome core particle, a small gene complete with promoter sequence, and the more complex, polynucleosomal 30 run fiber. Structural principles derived from these studies have direct application to gene control and expression. The primary objective will be to determine a medium to high resolution crystallographic structure of the nucleosome core particle. One or more crystal forms obtained by crystallization of nucleosomes reconstituted from purified histones and specific sequence DNA will be solved to a resolution of about 3 Angstroms using synchrotron radiation and heavy-atom derivative multiple wavelength anomalous diffraction phasing. One of the specific sequence DNAs under study consists of an entire tRNA gene with the polymerase III promoter site located near the center of the nucleosome (as it is in vivo). The structure and geometry of the promoter region and entire gene will be determined. This research program is designed to eventually provide the atomic resolution information which is of fundamental importance to a detailed understanding of gene expression, transcription, DNA replication, and the structures of DNA and chromatin. In conjunction with and complementary to the crystallographic work, studies will be initiated to obtain dynamical information concerning the functional relationships between structural elements within the 30 nm chromatin fiber. These studies will utilize neutron scattering and a viscous shear alignment system unique to Oak Ridge National Laboratory. A promising model for the organization of the 30 nm fiber will be tested using this system in conjunction with the power of contrast variation inherent to neutron scattering.