Surface science aspects of supramolecular conformation in elastin-like polypeptides

Polypeptides can form helical fibres in aqueous media: potentially useful for the production of biocompatible fabric and yarns. A previous work has shown that fibre formation occurs readily with elastin-like polypeptides constructed from hydrophobic amino acids, such as valine, glycine and leucine. However, elastin-like polypeptides, when suspended in methyl alcohol, are observed to form globules and 'string of bead' structures. Thus, it seems probable that the interface energy is important. Interface energy is minimised by the formation of bonds extending from one phase to the other: a phenomenon that is central to adhesion science. We have looked for evidence of such bonding using XPS to study structures formed by poly(ValGlyGlyLeuGly). The structures formed were first characterised by atomic force microscopy. Differences were found between structures and spectra formed in either water or methanol. No evidence for the presence of unique bonds characterising the interface was found, but evidence was found for the influence of a water environment on the internal structure, suggesting that it is the increase in intermolecular bonding opportunities associated with the influence of water on the growth of fibres that is the thermodynamic driver for the observed transformation into fibre deposits. Copyright (C) 2011 John Wiley & Sons, Ltd.