Restricted mobility of the sole tryptophan in membrane‐bound melittin

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Abstract
In spite of numerous studies, there appears to be no consensus regarding the orientation and aggregation state of membrane‐bound melittin. We report here the restricted environment of the sole tryptophan residue in membrane‐bound melittin using environment‐induced effects on the rates of solvent relaxation. When incorporated into unilamellar vesicles of dioleoyl‐sn‐glycero‐3‐phosphocholine (DOPC), melittin exhibits a red edge excitation shift (REES) of 5 nm. In addition, fluorescence polarization of melittin m the membrane shows both excitation and emission wavelength dependence. Taken together, these observations indicate that the tryptophan residue of melittin is located in a motionally restricted region in the membrane.