title: The thermodynamic analysis of protein stabilization by sucrose and glycerol against pressure-induced unfolding.
abstract: We have studied the reaction native left arrow over right arrow denatured for the 33-kDa protein isolated from photosystem II. Sucrose and glycerol have profound effects on pressure-induced unfolding. The additives shift the equilibrium to the left; they also cause a significant decrease in the standard volume change (DeltaV). The change in DeltaV was related to the sucrose and glycerol concentrations. The decrease in DeltaV varied with the additive: sucrose caused the largest effect, glycerol the smallest. The theoretical shift of the half-unfolding pressure (P1/2) calculated from the net increase in free energy by addition of sucrose and glycerol was lower than that obtained from experimental mea- surements. This indicates that the free energy change caused by preferential hydration of the protein is not the unique factor involved in the protein stabilization. The reduction in DeltaV showed a large contribution to the theoretical P1/2 shift, suggesting that the DeltaV change, caused by the sucrose or glycerol was associated with the protein stabilization. The origin of the DeltaV change is discussed. The rate of pressure-induced unfolding in the presence of sucrose or glycerol was slower than the refolding rate although both were significantly slower than that observed without any stabilizers.
authors.affiliation: Laboratory of Proteomics, Institute of Biochemistry and Cell Biology, Shanghai Institute for Biological Science, Chinese Academy of Sciences, Shanghai, China. kcruan@sunm.shcnc.ac.cn
authors.forename: Kangcheng
authors.initials: K
authors.lastname: Ruan
authors.forename: Chunhe
authors.initials: C
authors.lastname: Xu
authors.forename: Tingting
authors.initials: T
authors.lastname: Li
authors.forename: Jiong
authors.initials: J
authors.lastname: Li
authors.forename: Reinhard
authors.initials: R
authors.lastname: Lange
authors.forename: Claude
authors.initials: C
authors.lastname: Balny
mesh_terms: D005990:Glycerol / Q000494:pharmacology; D019791:Guanidine; D007700:Kinetics; D008970:Molecular Weight; D009994:Osmolar Concentration; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000187:drug effects / Q000302:isolation & purification; D045332:Photosystem II Protein Complex; D011489:Protein Denaturation; D012965:Sodium Chloride / Q000494:pharmacology; D013056:Spectrophotometry, Ultraviolet; D018724:Spinacia oleracea / Q000378:metabolism; D013395:Sucrose / Q000494:pharmacology; D013816:Thermodynamics
chemical_list: D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D012965:Sodium Chloride; D013395:Sucrose; D019791:Guanidine; D005990:Glycerol