The quenching of the fluorescence of biomacromolecules by solute quenchers has become a widely used and powerful technique (Lehrer, 1976; Lehrer and Leavis, 1989; Lakowicz, 1983; Eftink and Ghiron, 1981; Eftink, 1991). Such quenching reactions have been used primarily to obtain topographical information about proteins, nucleic acids, and membrane systems. The accessibility of intrinsic or extrinsic fluorescence probes (e.g., the amino acid, tryptophan), which are attached to a biomacromolecule, to small quenchers (e.g., iodide, acrylamide, oxygen) is directly determined by such reactions. Conformational changes in the biomacromolecule can then be monitored in terms of changes in the accessibility to the quencher of the fluorophore. In addition to such topographical information, in some cases information about the conformational dynamics of globular proteins has been obtained with solute quenching reactions.