Three-dimensional imaging of single molecules solvated in pores of poly(acrylamide) gels

Individual fluorescent molecules and individual singly labeled proteins were observed in the water-filled pores of poly(acrylamide) gels by far-field microscopy. Brownian motion was markedly reduced by the gel framework, thus enabling extended study of single fluorophores in aqueous environments. A highly axially dependent laser field was used both to excite the fluorophores and to image the molecules in three dimensions. Single molecules were followed as they moved within and through the porous gel structure. In contrast to dry polymeric hosts, these water-based gels may form a useful medium for single-molecule studies of biological systems in vitro.