Imaging single molecules in motion

Abstract

Continuous imaging of single molecules of a highly fluorescent compound and a fluorescent-tagged DNA has been achieved by postdoctoral associate Xiao-Hong Xu and chemistry professor Edward S. Yeung of the department of chemistry at Iowa State University, Ames [Science, 275, 1106 (1997)]. Imaging single biological molecules generally requires that they be immobilized in a polymer matrix or on a solid surface, or that their motion be frozen cryogenically. But such techniques don't show biological molecules in their natural environment—aqueous solution. Last year, chemistry professor W. E. Moerner of the University of California, San Diego, and coworkers devised an approach in which fluorescence microscopy and a charge-coupled device (CCD) detector were used to obtain discrete images of single fluorescent and tagged molecules in aqueous solution in the pores of polyacrylamide gels [Science, 274, 966 (1996)]. A series of these individual images could be combined into a kind of movie of molecular motion. Now...