SOLID-PHASE SYNTHESIS OF PEPTIDES MODELING TRANSMEMBRANE SEGMENTS OF BACTERIORHODOPSIN

Peptides modelling transmembrane segments C, D, E and G of bacteriorho dopsin were obtained by solid phase method using the conventional Boc strategy. Protected peptides were assembled on PAM polystyrene support . Side chain protecting groups were: Tos for Arg, Bzl for Thr and Ser, cHx for Asp and Glu, Bzl(Cl2) for Tyr, For for Trp, Z(Cl) for Lys. Sy ntheses were performed on a modernized Beckman 990 synthesizer in the automatic mode. Double couplings by a preformed hydroxybenzotriazole e ster were used for all residues. Qualitative and quantitative ninhydri ne tests were used to monitor coupling efficiency. Removal of protecti ng groups and peptide cleavage were achieved by hydrogen fluoride, con taining p-cresol and p-thiocresol as scavengers. Preparative reverse p hase HPLC was used for purification. Peptide structure and homogeneity were confirmed by amino acid analysis, H-1-NMR and analytical HPLC.