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An Infrared Spectroscopic Study of the Conformational Transition of Elastin-Like Polypeptides

Vesna Serrano ^*, Wenge Liu  and Stefan Franzen ^*

^* Department of Chemistry, North Carolina State University, Raleigh, North Carolina; and Department of Bioengineering, Duke University, Durham, North Carolina

Correspondence: Address reprint requests to Stefan Franzen, Dept. of Chemistry, North Carolina State University, Raleigh, NC 27695. Tel.: 919-515-8915; E-mail: stefan_franzen{at}ncsu.edu.

The infrared spectroscopy of elastin-like polypeptides and the relation to the inverse thermal transition are discussed. To correlate the spectroscopic observations with structure a density function theory model was created that captures the essential hydrogen bonding and packing of the ß-spiral structure proposed for elastin and elastin-like polypeptides. The infrared spectrum was calculated using periodic boundary conditions and a method for estimating the difference dipole moment permits both frequencies and intensities to be obtained for the modeling of spectra. The two observed amide I bands at 1615 cm^–1 and 1656 cm^–1 are shown to arise from the ß-spiral structure. The increase in intensity of these bands with increasing salt concentration and temperature is assigned to the closer association of strands of the ß-spiral. The sharp inverse temperature transition is observed within 1°C and involves a change in secondary structure that involves formation of interstrand ß-sheets for 25% of the amino acids. This conclusion is consistent with available data and simulations that have been reported to date.