Global analysis of distance distribution data for donor-acceptor pairs with different Förster distances

Distance distributions of a flexible molecule were recovered from steady-state fluorescence energy transfer measurements with the method suggested by Cantor and Pechukas In this method, the Forster distance (R0) is varied by attaching different donor-acceptor (D-A) pairs to the linker of interest. The distance distributions are recovered from the energy transfer efficiency measurements on D-A pairs with different R0s, followed by non-linear least squares fitting to distance distribution models. Thirteen compounds were synthesized with R0s ranging from 6-32 angstroms. Each compound contained a tryptamine donor linked by an alkyl chain (~10 carbon atoms) to one of thirteen different acceptors. The distance distributions were recovered by fitting the transfer efficiencies of the D-A pairs to both Gaussian and skewed Gaussian models. Our results indicate that the shape of the distribution is best described by a skewed Gaussian model. This is the first reported measurement of a skewed Gaussian distance distribution. In addition, the results of the Cantor and Pechuka's method and analysis were found to be consistent with distance distributions recovered from time-resolved frequency-domain fluorometry.