Anisotropy of Membrane-Bound Probes

Fluorescence anisotropy measurements have been used extensively to study biological membranes. These studies have their origin in the early studies of microviscosity of micelles and n mbranes. Tlie basic idea was to measure the aniscKr( y of a flucrophore in a refnence solvent of known viscosiQ and then in the membrane. The micro-viscosity of the membrane was then estimated by comparison with the viscosity calibration curve. 

At present, there is less use of the term microviscosity because it has been shown that fluorophoies in membranes diq lity con rlex anisotn decitys, which prevente a strittghtfcirwgd comparison of the solvent and memlirane data (Chqiler 11). Ifowever, steady-stale and tim e-solved anisotropies are still widely used became of the dramatic changes whidi occur at the membrane phase- 

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