UV resonance Raman study of angiotensin II conformation in nonaqueous environments: Lipid micelles and acetonitrile

We used 206.5‐nm excited resonance Raman measurements to examine the angiotensin II (AII) secondary structure in H 2 O in the presence of dodecylphosphocholine (DPC) micelles, sodium dodecylsulfate (SDS) monomers and micelles, and in a 70% acetonitrile (ACN‐d)–30% water solution. Our AII‐SDS titration absorption studies indicate the formation of a 1:2 AII:SDS complex in which two negatively charged SDS molecules attach to the AII positively charged N terminus and to Arg 2 . Our 206.5‐nm excited Raman results indicate that the 1:2 AII:SDS complexation increases the AII β‐turn composition. We also used 228.9‐nm Raman excitation to probe the local solvent accessibility of Tyr 4 (AII) in DPC and SDS micelles. Our Tyr (AII) solvent accessibility studies suggest that the Tyr residue is more exposed to the aqueous environment in SDS micelles than in DPC micelles. © 2000 John Wiley & Sons, Inc. Biopolymers (Biospectroscopy) 57: 55–63, 2000