The denaturation behaviour of calmodulin in sodium n-dodecyl sulphate, dodecyl trimethyl ammonium bromide, guanidine hydrochloride and urea

• Published in: Thermochimica acta Vol. 239; pp. 61 - 71
• Main Authors: Moosavi-Movahedi, A.A., Naderi, G.A., Farzami, B.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.07.1994; Elsevier Science
• Subjects: Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Molecular biophysics; Structure in molecular biology; Tridimensional structure; Binding protein; Thermodynamics; Calcium; Conformational dynamics; Denaturation; Refolding; Molecular interaction; Spatial structure; Calmodulin
• ISSN: 0040-6031; 1872-762X
• DOI: 10.1016/0040-6031(94)87056-X

The denaturation behaviour of calmodulin (CaM) in sodium n-dodecyl sulphate (SDS), dodecyl trimethyl ammonium bromide (DTAB), guanidine hydrochloride (GuHCl) and urea was studied by fluorescence spectrophotometry at 25 and 37°C in Tris-HCl buffer, pH 7.4. The sigmoidal denaturation curve was plotted in order to estimate the thermodynamic parameters, assuming a two-state mechanism in terms of the Pace model. SDS and DTAB, anionic and cationic surfactants, affect CaM on a millimolar level as a result of direct interaction between CaM and surfactant as an amphipatic molecule. GuHCl and urea affect CaM on a molar level as a result of indirect interaction with the surroundings of CaM (a change in the water structure). The thermodynamic data indicate a slight interaction in the case of SDS which induced incomplete unfolding of CaM. With DTAB, GuHCl and urea, unfolding of CaM took place to a much greater extent.