Fig. 7.

(a) The structure of dsDNA formed by complementary internally fluorescein-labeled 30-mer ssDNA and Cy3 labeled 66-mer ssDNA. The lifetime of fluorescein is 3.47 ns in ssDNA, and 1.60 ns in dsDNA due to FRET. (b) Average lifetimes obtained by iterative fitting (x-axis) vs. by the R-method (y-axis) from mixtures of ssDNA and dsDNA. The dashed diagonal line indicates that R-method results are identical to results of iterative fitting. Error bars represent STDs of lifetimes from 40,000 repeating measurements, each acquired with a total acquisition time of 132 μs.