(1) The Imaging Sciences Laboratory has a major collaborative research effort with the Institutes involving the use of image processing techniques and advanced computational techniques in structural biology to analyze electron micrographs and NMR spectra with the goal of determining macromolecular structures. Recent efforts have concentrated on the 3D reconstruction, analysis and interpretation of the structures of icosahedral virus capsids. Ongoing research involves analyses of structures related to herpesvirus and papillomairus as well as other icosahedral virus capsids. ? ? Papillomaviruses (e.g. HPV-16) encode two capsid proteins, L1 and L2. The major capsid protein, L1, can assemble spontaneously into a 72-pentamer icosahedral structure that closely resembles native virions. Although the minor capsid protein L2 is not required for capsid formation, it is thought to participate in encapsidation of the viral genome, and plays a number of essential roles in the viral infectious entry pathway. The abundance of L2 and its arrangement within the virion remain unclear. Cryo-electron microscopy and difference 3D reconstruction analysis of purified capsids revealed an icosahedrally-ordered L2-specific density beneath the axial lumen of each L1 capsomer. In addition, we have studied three biochemical constructs to try to determine how much L2 is contained within HPV-16 capsids. We have used time-lapse cryo-electron microscopy and image analysis to study the maturation of HPV-16 capsids assembled in 293T cells. The major capsid protein, L1, initially forms a loosely connected procapsid which, under in vitro conditions, condenses over several hours into the more familiar 60 nm-diameter papillomavirus capsid. In this process, the procapsid shrinks by 5% in diameter; its pentameric capsomers change in structure, most markedly in their axial region; and the interaction surfaces between adjacent capsomers are consolidated. These structural changes are accompanied by the formation of disulfide crosslinks that enhance the stability of the mature capsid. The C175S mutant, which does not crosslink, shows similar maturation-related structural changes but capsids are significantly larger, under otherwise similar conditions. We conclude that the observed structural size changes facilitates maturation, but crosslink formation is required to lock the capsid into the mature state. These results have been submitted for publication.? ? We have also been developing computational tools for the study of the structure and dynamics of biological macromolecules using NMR data. We are actively supporting the intra- and extramural communities which use the Xplor-NIH biomolecular structure determination software package. Development of Xplor-NIH has continued in the following areas: (a) further progress in the use of the Python and TCL scripting interfaces and the addition of extensive documentation; (b) the first realistic picture of the dynamical nature of DNA in solution has been obtained by combining information from NMR and Solution X-ray scattering techniques; (c) it is now possible to refine molecular structures directly against solution X-ray scattering and small-angle neutron scattering data; (d) the PASD facility for automated Nuclear Overhauser Effect peak assignment has been substantially improved; (e) a new structure refinement target has been introduced such that calculated protein structures have the correct molecular density.? ? (2) The Imaging Sciences Laboratory has a commitment to providing computational and engineering expertise to a variety of clinical and biomedical activities at NIH. Specifically, PET, ultrasound, CT, MRI, microscopy, imaging in cancer research, and imaging related to neural dysfunction have been supported in a number of ways. Tosupport scientific in the NIH intramural program, CIT has developed and continues to enhance a sophisticated platform-independent, n-dimensional, extensible image processing and visualization application. The MIPAV (Medical Image Processing Analysis and Visualization) is an application that enables quantitative analysis and visualization of biomedical imaging modalities (from micro to macro) and is used by researchers at NIH and around the world. At NIH, MIPAV has been used to analyze anatomical structures in CT datasets, assist in pretreatment analysis (registration and segmentation) of image datasets associated with radio frequency ablation (RFA) procedures, analysis of MRI datasets for NIMH, and has been used by NCI for the analysis of 2D and 3D microscopic samples. We also continue to support the NEI with research of diseases of the eye and support analysis of image data from the Osteoarthritis Initiative, a nationwide research study sponsored by the National Institutes of Health, that will help us better understand how to prevent and treat knee osteoarthritis. In addition, we manage and develop major components of the National Database for Autism Research (NDAR) project which is a collaborative biomedical informatics system created by the National Institutes of Health to provide a national resource to support and accelerate research in autism. NDAR is a collection of information systems supporting the full range of autism research activities, including genomic, imaging, laboratory, clinical, and behavioral data sources. It will provide the core technology for a data warehouse, a data-entry system, and a centralized source for common measures and their documentation. It will support large-scale, multi-site projects as well as pilot studies and basic science investigations.
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