Proton transfer reactions

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  • Acid: vị chua, làm thuốc nhuộm đổi màu Bases: vị đắng, cảm giác nhớt. Arrhenius: acids làm tăng [H+], bases làm tăng [OH-] trong dung dịch. Arrhenius: acid + base  salt + water. Problem: định nghĩa này chỉ áp dụng được trong dung dịch nước The H+ Ion in Water The H+(aq) ion is simply a proton with no electrons. (H has one proton, one electron, and no neutrons.) In water, the H+(aq) form clusters. The simplest cluster is H3O+(aq). Larger clusters are H5O2+ and H9O4+. Generally we use H+(aq) and H3O+(aq) interchangeably....

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  • The solubility of a partially soluble salt is decreased when a common ion is added. Consider the equilibrium established when acetic acid, HC2H3O2, is added to water. At equilibrium H+ and C2H3O2- are constantly moving into and out of solution, but the concentrations of ions is constant and equal. If a common ion is added, e.g. C2H3O2- from NaC2H3O2 (which is a strong electrolyte) then [C2H3O2-] increases and the system is no longer at equilibrium. So, [H+] must decrease.

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  • The roles of His181, His184 and Tyr186 in PETN reductase have been examined by mutagenesis, spectroscopic and stopped-flow kinetics, and by determination of crystallographic structures for the Y186F PETN reductase and reduced wild-type enzyme—progesterone complex. Residues His181 and His184 are important in the binding of coenzyme, steroids, nitro-aromatic ligands and the substrate 2-cyclohexen-1-one.

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