| Title: | Homotropic cooperative binding of organic solvent vapors by solid trypsin |
| Author(s): | Gorbatchuk VV; Ziganshin MA; Mironov NA; Solomonov BN; |
| Address: | "Department of Chemistry, Kazan State University, Kremlevskaya 18, 420008, Kazan, Russia. valery.gorbatchuk@ksu.ru" |
| DOI: | 10.1016/s0167-4838(00)00298-3 |
| ISSN/ISBN: | 0006-3002 (Print) 0006-3002 (Linking) |
| Abstract: | "Homotropic cooperative binding was observed at vapor sorption of organic solvents (acetonitrile, propionitrile, ethanol, 1-propanol, 2-propanol, nitroethane) by dried solid trypsin from porcine pancreas (0.05 g H2O/g protein). The vapor sorption isotherms were obtained by the static method of gas chromatographic headspace analysis at 298 K for 'vapor solvent+solid trypsin' systems in the absence of the liquid phase. All isotherms have a sigmoidal shape with significant sorbate uptake only above the threshold of sorbate thermodynamic activity. On the sorption isotherms of non-hydroxylic sorbates the saturation of trypsin by organic solvent was observed above the sorbate threshold activity. The formation of inclusion compounds with phase transition between solvent-free and solvent-saturated trypsin is supposed. Approximation of obtained isotherms by the Hill equation gives the inclusion stoichiometry S, inclusion free energy, and the Hill constant N of clathrates. The inclusion stoichiometry S depends significantly on the size and shape of sorbate molecules and changes from S=31 mol of sorbate per mol of trypsin for ethanol to S=6 for nitroethane. The inclusion free energies determined for the standard states of pure liquid sorbate and infinitely dilute solution in toluene are in the range from -0.5 to -1.2 kJ/mol and from -3.1 to -8.1 kJ/mol, respectively, per 1 mol of sorbate. The Hill constants are relatively high: from N=5.6 for 1-propanol to N approximately equal to 10(3) for nitroethane. The implication of the obtained results for the interpretation of solvent effects on the enzyme activity and stability in low-water medium is discussed" |
| Keywords: | "1-Propanol/metabolism Acetonitriles/metabolism Animals Chemical Phenomena Chemistry, Physical Chromatography, Gas Ethane/analogs & derivatives/metabolism Ethanol/metabolism Nitriles/metabolism Nitroparaffins/metabolism Pancreas/enzymology Protein Binding;" |
| Notes: | "MedlineGorbatchuk, V V Ziganshin, M A Mironov, N A Solomonov, B N eng Comparative Study Research Support, Non-U.S. Gov't Netherlands 2001/05/09 Biochim Biophys Acta. 2001 Feb 9; 1545(1-2):326-38. doi: 10.1016/s0167-4838(00)00298-3" |
