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

¹ North Carolina State University
² Duke University

^* To whom correspondence should be addressed. E-mail: stefan_franzen{at}ncsu.edu.

Submitted on December 31, 2006
Revised on February 16, 2007
Accepted on 20 April 2007

	Abstract

The infrared spectroscopy of elastin-like polypeptides (ELPs) and the relation to the inverse thermal transition are discussed. In order to correlate the spectroscopic observations with structure a density function theory (DFT) model was created that captures the essential hydrogen bonding and packing of the -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 -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 -spiral. The sharp inverse temperature transition is observed within 1 °C and involves a change in secondary structure that involves formation of interstrand -sheets for approximately 25% of the amino acids. This conclusion is consistent with available data and simulations that have been reported to date.

Key Words: Aggregation, Beta-sheet, Beta-spiral, Coacervation