Question

The fluorescence lifetime of a dye used as the donor molecule for FRET is 4.0ns. In the presence of the acceptor the lifetime of the donor decreases to 1.8ns. a) Calculate the efficiency of energy transfer for this donor-acceptor pair. b) If the Foster radius for this pair R0 is 40A, calculate the distance (in Angstroms) between the donor and the acceptor assuming that in this sample the value of k2=2/3.

Answer 1

The equation of FRET efficiency or efficiency of energy (E) = 1-(T₁ / T₂),

Where, T₁ = Donor lifetime in presence of acceptor

T₂ = Donor lifetime in absence of acceptor

E = 1 - (1.8 / 4)

= 0.55

Now to calculate the distance between donor and acceptor we will use the following equation

E = 1 / [1 + (r / R₀)⁶]

Where, E is energy efficiency

r is distance between donor and acceptor

R₀ radius of the given pair

0.55 = 1 / [1 + (r / 40)⁶]

r = 32.72 A°