[Solid-phase synthesis of peptides modelling the transmembrane segment of bacteriorhodopsin]

Peptides modelling transmembrane segments C, D, E and G of bacteriorhodopsin 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. Syntheses were performed on a modernized Beckman 990 synthesizer in the automatic mode. Double couplings by a preformed hydroxybenzotriazole ester were used for all residues. Qualitative and quantitative ninhydrine tests were used to monitor coupling efficiency. Removal of protecting groups and peptide cleavage were achieved by hydrogen fluoride, containing p-cresol and p-thiocresol as scavengers. Preparative reverse phase HPLC was used for purification. Peptide structure and homogeneity were confirmed by amino acid analysis, 1H-NMR and analytical HPLC.