Funds are requested for the purchase of a JEM-1200EXII transmission electron microscope. An estimated 60 hours/week of electron microscopy is needed for 13 existing NIH grants and 8 hours/week for non-NIH grants. Sufficient time will not be available on existing instruments. At the Pennsylvania State University there are six transmission electron microscopes; one is 6 years old (Philips EM-420), one is 12 years old (Philips EM-420) and four are 20-24 years old. None of the microscopes for biological samples can be reliably operated for high resolution studies or for quantitative elemental analysis. The instrument is requested for a multiuser group, comprised of 8 investigators: four will investigate structure-function relationships of isolated proteins (dynein ATPase, DNA polymerase, glutamine synthetase and adenylyl transferase) and four will investigate various aspects of cells and their organelles (osteoclasts, sperm, lung cells, and pituitary cells. Participating departments include Molecular and Cell Biology, Chemistry and Veterinary Science. In addition, three of the investigators cooperate as members of the Center for Cell Research. The electron microscope facility is centrally located for all investigators. The instrument will be operated on a user-free basis designed to cover operational and maintenance costs. The University has made definitive commitments for the establishment and maintenance of a functional electron microscope facility as a joint effort of the Colleges of Science and Agriculture. The principal investigator is experienced in managing a multi-user electron microscope facility. Appropriate technical support staff are available.