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 angiot ensin II (AII) secondary structure in H2O in the presence of dodecylphospho choline (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 whic h 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 beta-turn composition. We a lso 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 accessibili ty studies suggest that the Tyr residue is more exposed to the aqueous envi ronment in SDS micelles than in DPC micelles. (C) 2000 John Wiley & Sons, I nc.