Forster energy transfer experiments from Trp residues to calcofluor white

Forster energy transfer experiments from Trp residues to calcofluor white 

The decrease of the fluorescence intensity of the Trp residues in presence of calcofluor white is the result of an energy transfer Forster type from the Trp residues to the extrinsic probe. The efficiency of this energy transfer depends on three parameters, the distance R between the donor (Trp residues) and the acceptor (calcofluor white), the spectral overlap between the fluorescence spectrum of the donor and the absorption spectrum of the acceptor and the orientation factor k which gives an indication on how the dipoles of acceptor in the fundamental state and donor in the excited state are aligned. 

The Forster distance R (in cm) at which the efficiency of energy transfer is 50% was calculated with equation 12  

Ro is found equal to 17.3 A. This small distance suggests the presence of a weak energy transfer between Trp residues and calcofluor white. 

The value of E calculated at infinite concentrations of calcofluor white was obtained by plotting 1/E as a function of l/[calcofluor white] (Fig. 8.39). E was found equal to 0.45. 

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