Multichromophoric Förster Resonance Energy Transfer

The theory of Förster resonance energy transfer is generalized for multichromophoric (MC) and nonequilibrium situations. For the first time, it is clarified that the far-field linear spectroscopic information is insufficient for the determination of the reaction rate and that distance dependence of the rate can vary with the disorder and temperature. Application to a light harvesting complex LH2 reveals the important consequences of a MC structure.

Figure 1

(a) Transition dipoles of $D$, $A_{\alpha }$, and $A_{\beta }$. All the vectors and coordinates are in the same plane. (b) Values of $\kappa =k_F^{\mathrm{MC}}{R}^6/({\mu }_D^2{\mu }_A^2)$ vs $R$, for Cases I and II, at $k_{B}T=0.1$ (LT) and $k_{B}T=1$ (HT). (c) Comparison of the expression of MAS-SF with Eq. (10), for Case II at $k_{B}T=0.1$.

Figure 2

(a) Distributions of FRET rates. The scale factor $S_f$, assuming unit refractive index, is ${10}^9/{\mu }_{\mathrm{BChl}}^4$ in the units where $\hslash =c=1$ and $1\mathrm{\AA }$ is the unit length. In applying Eq. (1), a unit orientational factor and the shortest ${\mathrm{BChl}}_{\mathrm{B}800}\mathrm{\text{−}}{\mathrm{BChl}}_{\mathrm{B}850}$ distance were used. The vertical scale of the distribution for Eq. (1) has been reduced by a factor of 7. (b) Logarithmic populations. $[P_D(t){]}_{av}=⟨\exp (-kt)⟩$ and $k_{av}=⟨k_F^{\mathrm{MC}}⟩$.