MOLECULAR DYNAMICS REFINEMENT WITHOUT DECONVOLUTION IN FIBER DIFFRACTION OF BIOLOGICAL POLYMERS. Gerald Stubbs and Hong Wang, Department of Molecular Biology, Vanderbilt University, Nashville, Tennessee 37235

There is useful information in a fiber diffraction pattern even beyond the resolution at which layer lines overlap. Most fiber diffraction studies involving large monomers have been limited to the non-overlapping region of the pattern, since objective determination of a molecular structure depends on complete phasing of separated diffraction intensities. Once a model has been constructed, however, there is no reason to discard higher resolution data. Makowski has shown that beyond the point where layer lines can be deconvoluted, the information content of a diffraction pattern continues to increase with resolution, although only linearly. The most powerful method of refinement of macromolecular structures currently available is molecular dynamics refinement, for example as used in our adaptation of the program X-PLOR to use fiber diffraction data. We have further modified X-PLOR to handle undeconvoluted data. In addition to atomic coordinates, global parameters such as specimen disorientation are refined. Testing so far has been against simulated and real helical virus data. Supported by NSF grant MCB 9506204.