Two studies are described in which synthetic peptides have been designed and examined to address biochemical problems inherent in hydrophobic environments (1) The cyclic hexapeptide cycl~(&Tyr(Bzl)-Gly-Ile-Leu-Gln-Pro) was synthesized as a model of an interior P-turn from the protein lysozyme. Conformational analysis by proton nmr methods, including two-dimensional nuclear Overhauser effect spectroscopy, revealed that the model peptide adopts one conformation in chloroform/dimethyl sulfoxide (982) and tetramethylene sulfone solutions. The conformation consists of two linked P-turns, one with the same sequence (Gly-Ile-Leu-Gln) and geometry (Type I) as the protein turn.
(2) Major portions of the A-receptor protein (LamB) signal sequences from E. coli wildtype and mutant strains have been synthesized. The conformational properties and membrane interactions of these synthetic signal peptides correlate with the in uiuo export function of the wild type and mutant strains. Functional signal sequences are significantly richer in a-helix in aqueous trifluoroethanol, lysolecithin, or sodium dodecyl sulfate solution than is a nonfunctional mutant signal sequence.
* Dedicated to Elkan R. Blout on the occasion of his sixty-fifth birthday.