Raman spectroscopic study of tropomyosin denaturation

✍ Scribed by B. G. Frushour; J. L. Koenig

• Publisher: Wiley (John Wiley & Sons)
• Year: 1974
• Tongue: English
• Weight: 544 KB
• Volume: 13
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.1974.360130913

✦ Synopsis

Abstract

Raman spectra of the pH denaturation of tropomyosin are presented. In the native state tropomyosin has an alpha‐helical content of nearly 90%, but this value drops rapidly as the pH is raised above 9.5. The Raman spectrum of the native state is characterized by a strong amide I line appearing at 1655 cm^−1^, very weak scattering in the amide III region around 1250 cm^−1^, and a medium‐intensity line at 940 cm^−1^. When the protein is pH‐denatured, a strong amide III line appears at 1254 cm^−1^ and the 940 cm^−1^ line becomes weak. The intensities of the latter two lines are a sensitive measure of the alpha‐helical and disordered chain content. These results are consistent with the helix‐to‐coil studies of the polypeptides.

The Raman spectra of α‐casein and prothrombin, proteins thought to have little or no ordered secondary structure, are investigated. The amide III regions of both spectra display strong lines at 1254 cm^−1^ and only weak scattering is observed at 940 cm^−1^, features characteristic of the denatured tropomyosin spectrum. The amide I mode of α‐casein appears at 1668 cm^−1^, in agreement with the previously reported spectra of disordered polypeptides, poly‐L‐glutamic acid and poly‐L‐lysine at pH 7.0 and mechanically deformed poly‐L‐alanine.