Differential scanning calorimetry of the irreversible denaturation of Rapana thomasiana (marine snail, Gastropod) hemocyanin

✍ Scribed by Krassimira Idakieva; Katja Parvanova; Svetla Todinova

• Book ID: 104003390
• Publisher: Elsevier Science
• Year: 2005
• Tongue: English
• Weight: 257 KB
• Volume: 1748
• Category: Article
• ISSN: 1570-9639
• DOI: 10.1016/j.bbapap.2004.12.004

✦ Synopsis

The thermal denaturation of the hemocyanin from gastropod Rapana thomasiana (RtH) at neutral pH was studied by means of differential scanning calorimetry (DSC). The denaturation was completely irreversible as judged by the absence of any endotherm on rescanning of previously scanned samples. Two transitions, with apparent transition temperatures (T m ) at 83 and 90 8C, were detected by DSC using buffer 20 mM MOPS, containing 0.1 M NaCl, 5 mM CaCl 2 and 5 mM MgCl 2 , pH 7.2. Both T m were dependent on the scanning rate, suggesting that the thermal denaturation of RtH is a kinetically controlled process. The activation energy (E A ) of 597F20 kJ mol À1 was determined for the main transition (at 83 8C). E A for the second transition was 615F25 kJ mol À1 . The T m and DH cal values for the thermal denaturation of RtH were found to be independent of the protein concentration, signifying that the dissociation of the protein into monomers does not take place before the rate-determining state of the process of thermal unfolding.