Structural transition during thermal denaturation of collagen in the solution and film states

Abstract

Temperature dependent vibrational circular dichroism (VCD) spectra of type I collagen, in solution and film states, have been measured. These spectra obtained for solution sample suggest that the thermal denaturation of collagen results in transition from poly-L-proline II (PPII) to unordered structure. The PPII structure of collagen is identified by the presence of negative VCD couplet in the amide I region, while the formation of unordered structure is indicated by the disappearance of VCD in the amide I region. The temperature dependent spectra obtained for the supported collagen film indicated a biphasic transition, which is believed to be the first vibrational spectroscopic report to support a biphasic transition during thermal denaturation of collagen film. The temperature dependent spectra of collagen films suggest that the thermal stability of collagen structure depends on its state and decreases in the order: supported film > free standing film > solution state. These observations are believed to be significant in the VCD spectroscopic analysis of secondary structures of proteins and peptides.

Mini review: Instrumentation for vibrational circular dichroism spectroscopy, still a role for dispersive instruments

“…As with all CD measurements, scatter from particulate formation is detrimental, but because of the longer wavelengths used in the IR, and shorter path length cells, this problem is much less severe than for ECD. We and others have succeeded in measuring spectra of aggregated samples, fibrils, and films, as well as of proteins in membrane vesicles . In all these less ideal samples, care must be taken to assure that the spectra are not distorted by macroscopic characteristics of the sample.…”

Isotope-assisted vibrational circular dichroism investigations of amyloid β peptide fragment, Aβ(16–22)

“…The signs and shapes of VCD bands for different secondary structures are different, in addition to vibrational band positions or frequencies. For example, right handed a-helical structure is associated with positive VCD couplet centered at $1655 cm À1 (positive band at $1645 cm À1 followed by negative band at $1667 cm À1 ) (Keiderling, 1986) while the left handed polyproline II like structure is associated with negative VCD couplet centered at $1650 cm À1 (negative band at $1640 cm À1 followed by positive band at $1665 cm À1 ) (Dukor and Keiderling, 1991;Shanmugam and Polavarapu, 2009). Proteins with b-sheet structures are found to yield negative VCD band in the 1610-1630 cm À1 region (Keiderling, 1986;Shanmugam and Polavarapu, 2004).…”

A Solid Phase Vibrational Circular Dichroism Study of Polypeptide–Surfactant Interaction

“…The technique of vibrational circular dichroism (VCD) provides sensitive and specific information in the analysis of chiral compounds. It is well established for the study of peptide solution structure and as such has been used to study both protein and peptides not only in aqueous and organic solutions environments but also in model membranes, micelles, and other interfaces …”