FIGURE 1.

Scheme illustrating the procedures for studies of presynaptic (A) and synaptic (B) SfiI-DNA complexes. (A) The DNA duplex tagged with Cy3 (D in green burst) was used for detecting the formation of the presynaptic complex. (B) Two DNA duplexes tagged with Cy3 and Cy5 (A in red burst) dyes are bound to protein tetramer to form the Forster pair. The fluorescence of the acceptor molecule (Cy5) is observed only in the synaptic complex upon energy transfer from the excited donor molecule. The laser beam was focused directly on the surface (not shown). Diameter of the laser beam is ∼0.5 μm.