| Autor: |
Walker, John M., Vulfson, Evgeny N., Holland, Herbert L., Partridge, Johann, Harper, Neil, Moore, Barry D., Halling, Peter J. |
| Zdroj: |
Enzymes in Nonaqueous Solvents; 2001, p227-234, 8p |
| Abstrakt: |
The catalytic activity of an enzyme is profoundly affected by its ionization state, whether it is dissolved in aqueous solution or suspended in low-water organic media. In aqueous solution, counterions can freely move around in a solution. Because they are not closely associated with opposite charges, their identity does not effect the protonation state of the enzyme; thus, pH alone governs the protonation state. When a biocatalyst is suspended in a low-water organic solvent, the situation is more complex. In this case, counterions are in closer contact with the opposite charges on the enzyme because of the lower dielectric constant of the medium. Thus, protonation of ionizable groups on the enzyme will be controlled by the type and availability of these ions as well as hydrogen ions. Changes in ionization state of the protein can therefore be described by two equilibria that can, in theory, be controlled independently (1,2) [ABSTRACT FROM AUTHOR] |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
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