In an experiment to investigate the folding of tethered labelled peptides using fluorescence resonant energy transfer, the quantum yield for fluorescence of a rhodamine dye donor was found to decrease, on average, by a factor of 0.21 in the presence of a Texas red dye acceptor. Use the Förster theory of resonant energy transfer to determine the separation of the donor-acceptor pair, given that the Förster distance parameter for the rhodamine-Texas red pair is R₀ = 4.4 nm.

Question

Quizplus · Accepted Answer

The Förster theory of resonant energy transfer states that the efficiency of energy transfer (E) is inversely proportional to the sixth power of the distance (r) between the donor and acceptor, given by $E = 1/(1+(r/R_0)^6)$, where $R_0$ is the Förster distance. Given that the quantum yield decreases by a factor of 0.21, the efficiency of energy transfer is $E = 1 - 0.21 = 0.79$. Rearranging the formula to solve for $r$ and substituting $E = 0.79$ and $R_0 = 4.4$ nm, we find that $r$ is approximately 3.5 nm.

In an Experiment to Investigate the Folding of Tethered Labelled