Biological Systems Involving Proton Transfers

Other reviews on proton transfer deal with the following topics hydrogen bonding and H+ transfer " , general acid/base catalysis " and proton transfers in biological systems involving proteins . 

Proton transfer is one of the simplest of all elementary chemical processes, the kinetics of which play an important role in many biological processes. Many examples of tautomerism (the equilibrium between two different isomers) involve proton transfer. Of the many systems studied the photon-stimulated Excited State Intramolecular Proton Transfer (ESIPT) in 3-hydroxyfiavone (3-HF) (C15 Hio O3), which is an important plant compound, has many desirable features, making it an ideal model system. 

Tliere are several reasons for this great interest in the tautomerism of porphyrins (which could justify its own review) (1) their biological significance, (2) their applications in material science ( hole burning is related to their tautomerism), (3) the simplicity of the system (annular tautomerism involving intramolecular proton transfer both in solution and in the solid state), and (4) the possibility of elucidating the kinetic processes in great detail. 

OH ions has the very high value of 1.3 x 10 M s" h The actual chemical interaction between a hydrogen and a hydroxide ion, when they come together, involves little or no activation energy the rate which is measured is the rate with which the ions diffuse past the surrounding water molecules. Diffusion control is often found with proton-transfer and electron-transfer processes, which are very rapid. Such processes commonly occur in biological systems, where diffusion control is therefore very important. 

Most reactions that occur in living cells are some form of oxidation-reduction reactions. Oxidation-reduction reactions must occur together, since no substances can lose electrons without another substance gaining electrons. In biological systems, oxidation-reduction reactions involve not only transfer of electrons but also transfer of hydrogen that has both one proton (H+) and one electron. Oxidation of H2 gas will result in the release of H+ and one electron ... 

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