The interactions between biological macromolecules and macromolecular assemblies are central to the proper functioning of biological systems. These interactions have been measured by techniques that measure the averaged interactions of large ensembles of particles. Recently, a number of experimental approaches have been developed that enable the study of single molecules, thus the distributions that make up the average behavior and the heterogeneity of a population can be determined as can the time-dependent behavior of the molecules. Interactions between individual molecules depend on many variables including separation distance, orientation, conformation, and local environment. Two single molecule techniques, atomic force microscopy (AFM) and single-molecule fluorescence spectroscopy, if used simultaneously, are sensitive to those parameters. Here we present an instrument that combines AFM with confocal and total internal reflection microscopy and report on progress towards the simultaneous measurement of force and orientational and conformational dynamics of single bio-molecules in aqueous conditions.
William F. Heinz
Optical Technology Division, NIST
100 Bureau Dr., Mail Stop 8442, Gaithersburg, MD 20899-8442 USA