Conformational studies on synthetic polypeptides: poly (d-phenylglycine) and poly(d-cyclohexylglycine) |
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Authors: | M Palumbo A Cosani M Terbojevich E Peggion |
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Affiliation: | Biopolymer Research Centre of CNR, Institute of Organic Chemistry, Via Marzolo, 1-35100 Padova, Italy |
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Abstract: | Poly(d-phenylglycine) and poly(d-cyclohexylglycine) containing phenyl and cyclohexyl rings bound to the α-carbon of the polypeptide chain, have been synthesized. Circular dichroism measurements show that both polymers undergo a conformational transition from the random-coil form to an ordered form, upon addition of water, ethanol or trifluoroethanol to sulphuric acid solutions. Solid state measurements indicate that the ordered structures of poly(d-phenylglycine) and poly(d-cyclohexylglycine) are of the β-type. While for the former the antiparallel arrangement is predominant, for the latter there seems to be a greater tendency towards the parallel form. The ordered form of poly(d-cyclohexylglycine) is slightly more stable than the corresponding form of poly(d-phenylglycine) in all the above solvent systems. This can be interpreted in terms of stronger non covalent bond formation in the former polypeptide. Our results have been compared with literature on poly(l-phenylalanine) and poly(l-cyclohexylalanine). |
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