Unfolding of Ervatamin C in the Presence of Organic Solvents: Sequential Transitions of the Protein in the O-state

Abstract

The folding of ervatamin C was investigated in the presence of various fluorinated and non-fluorinated organic solvents. The differences in the unfolding of the protein in the presence of various organic solvents and the stabilities of O-states were interpreted. At pH 2.0, nonfluorinated alkyl alcohols induced a switch from the native α-helix to a β-sheet, contrary to the β-sheet to α-helix conversion observed for many proteins. The magnitude of ellipticity at 215 nm, used as a measure of β-content, was found to be dependent on the concentration of the alcohol. Under similar conditions of pH, fluorinated alcohol enhanced the intrinsic a-helicity of the protein molecule, whereas the addition of acetonitrile reduced the helical content. Ervatamin C exhibited high stability towards GuHCl induced unfolding in different O-states. Whereas the thermal unfolding of O-states was non-cooperative, contrary to the cooperativity seen in the absence of the organic solvents under similar conditions. Moreover, the differential scanning calorimetry endotherms of the protein acquired at pH 2.0 were deconvoluted into two distinct peaks, suggesting two cooperative transitions. With increase in pH, the shape of the thermogram changed markedly to exhibit a major and a minor transition. The appearance of two distinct peaks in the DSC together with the non-cooperative thermal transition of the protein in O-states indicates that the molecular structure of ervatamin C consists of two domains with different stabilities.

Differential Scanning Calorimetry in Life Science: Thermodynamics, Stability, Molecular Recognition and Application in Drug Design

“…The thermostability and thermal denaturation of other enzymatic systems, like PsbQ protein of higher plant photosystem II [51], ervatamin C [52], progenipoietin [53],…”