title: Synthesis and conformation of sequential polypeptides of L-alanine and beta-aminobutyric acid.
abstract: Sequential polypeptides with the repeating units L-alanyl-(S)-beta-aminobutyric acid, L-alanyl-(R)-beta-aminobutyric acid, and L-alanyl-(R,S)-beta-aminobutyric acid have been synthesized by polycondensation of the N-hydroxysuccinimide ester hydrochloride salts of the corresponding dipeptides. Circular dichroism and infrared spectroscopy studies of films of the polypeptides and circular dichroism study of their solutions in hexafluoro-2-propanol and hexafluoropropane-2,2-diol show the tendency of the polypeptides to adopt the beta conformation in the solid state. In pure hexafluoro-2-propanol or hexafluoroacetone, the three polymers adopt what we interpret as random coil conformations. In mixtures of hexafluoro-2-propanol-water or hexafluoropropane-2,2-diol-water, the polypeptide containing the S isomer shows a definite tendency to form beta structure. This tendency is not established for the R and the R,S isomers.
mesh_terms: D000409:Alanine; D000613:Aminobutyrates; D002942:Circular Dichroism; D010455:Peptides / Q000138:chemical synthesis; D011487:Protein Conformation; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet
chemical_list: D000613:Aminobutyrates; D010455:Peptides; D000409:Alanine