Effect of Emission Maximum on Quenching

For wat -soluble quenchers, which do not readily penetrate die hydrophobic regions d proteins, diere is a strong ccxTcladon between die emission maximum and quenching constant Blue-shifted tryptqihan residues are essm-tially inaccessible to quenching by acrylamide, and 

The extent of coUtaonal quenching can also be dependent on protein conformation andfor the extent of subunit assodalion. This fect has bean iHuslrated for melittin, 

Fractional AccessHiility to Quenching in Multi-Tryptophan Proteins 

As described in Section 8.8, the fraction of accessible fluorescence ( ) can be obtained from a modified Slem- Umerplol, in which fo/AFis plotted versus reciprocal quencher concentration. The ) inteToept represents extrapolation to infinite quencher concentration. Complete quenching is expected for an accessible fluorophore. so Fo/AF is unity. If a portion of the fluorescence is not accestible, AF is smaller than Fo. and the intercept (/ ) is greater than unity. 

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