Grotthus mechanism, hydrogen bonds

Figure 2.18 Schematic of the Grotthus mechanism of long-range proton transfer in water molecules. In this, hydrogen bonds and covalent bonds interchange, releasing a proton from one end of the chain as a new proton is introduced at the start of the chain...

The energy released by electron transfer can be used in the transport of protons through the membrane. One of the proton conduction mechanisms in proteins is through a chain of hydrogen bonds in the protein, i.e. a Grotthus mechanism (Section 2.9), similar to the mechanism of proton movement in ice. Protons are injected and removed by the various oxidation/reduction reactions which occur in the cell there is no excess of protons or electrons in the final balance, and the reaction cycle is self-sustaining. 

Counted among these superionic electrolytes are the solutions of strong acids in water and other hydrogen-bonded solvents (e.g., glycerol, hydrogen peroxide) in which the proton has anomalously high mobility due to the Grotthus mechanism... 

Polarisation of the substrate carbonyl group appears to be achieved in yet a third way by mammalian glucose 6-phosphate isomerase, which interconverts glucose and fructose 6-phosphates, The crystal structure of the rabbit enzyme in complex with the reactive intermediate analogue o-arabinohydroxamic acid Ki = 0.2 pM) (in its hydroximic form) reveals a cluster of four water molecules hydrogen bonded to each other, to the counterparts of 01 and 02 of the enediolate intermediate and to an active site arginine. Grotthus mechanisms of proton transfer between the two tautomers of the enediolate probably occur. 

Lagodzinskaya GV, Yunda NG, ManeUs GB (2002) H + -catalyzed symmetric proton exchange in neat liquids with a network of N-H-N and O-H-O hydrogen bonds and molecular mechanism of Grotthus proton migration. Chem Phys 282 51-61 Lamb WJ, Brown DR, Jonas JJ (1981) Temperature and density dependence of the proton lifetime min liquid water. Phys Chem 85 2883-1887... 

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