Atomic Force Microscopy (AFM) is a relatively new technology that permits observation of surface topology down to the atomic level. In its most commonly used modality, a silicon nitrite probe honed to molecular dimensions is oscillated vertically while traversing an area of the sample in an XY scanning mode. Deflects of the tip are recorded by a laser diode-positional detector system and are used to derive a three- dimensional image of the surface of the specimen. The instrument can operate in are or in a fluid chamber and permit the imaging of living cells, individual proteins and DNA molecules, and biological membranes in their native state, and thus can provide time-lapse views of cellular and molecular interactions under physiologic conditions. Modulations in tip deflection can also be used to measure the attractive force between individual receptor-ligand pairs by coating the tip and specimen surface with each of the two molecules. AFM has wide variety of applications to biological systems. In this Shared Instrument Grant, we have assembled a group of 8 NIH- funded investigators at the University of Texas Health Science Center at Houston and the Texas A&M University Institute of Biosciences and Technology whose research would be enhanced significantly by the availability of an AFM. Administrative and technical support of the instrument will be provided by the Principal Investigator, a Technical Director who will coordinate the day-to-day maintenance, access, and training, a Supervisory Board who will monitor and optimize instrument utilization, and an Advisory Board of users who will meet on a monthly basis. Data and journal club presentations will be incorporated into these monthly meetings to expose users to the latest applications and to encourage collaborations. Space, maintenance, and upgrading of the instrument will be provided by the Department of Pathology and Laboratory Medicine (where the AFM will be housed) and by the University of Texas Medical School. It is anticipated that many additional users will be recruited once availability of the instrument and its capabilities become more widely known through the Texas Medical Center.