Charge transfer complexes, biological systems

Sometime in the past decade, probably around 1982-1984, the collective imagination of electroanalytical chemists absorbed the connections among such diverse areas as solid-state chemistry, fabrication of solid-state devices, semiconductors, polymer morphology, surface and interfacial chemistry, membrane chemistry and technology, biochemistry, and catalytic mechanisms. Before the advent of electrodes modified with multilayers of polymers, these areas of endeavor were each distinct within the electroanalytical mind. Once charge transport could be observed in such a simultaneously simple and complex system as a redox polymer film, the relevance of charge transfer in biological systems, and at the surfaces of solids and membranes, became apparent. A 1984... 

This review will be concerned with recent progress made towards an understanding of conduction phenomena in typical homomolecular crystals, e.g. anthracene and the phthalocyanines, with certain charge-transfer complexes, selected biological systems, certain novel one-dimensional systems and other materials which serve to illustrate a particular theoretical approach or the value of an experimental technique. Little attention will be given to experimental procedures other than when these are not in common use and have not been adequately described in the earlier reviews. 

R. Boyer, Concepts in Biochemistry, Brooks/ Cole, Monterey, CA, 1999. See also F. Gutmann, C. Johnson, H. Keyzer, J. Molnar, Charge-Transfer Complexes in Biological Systems, Dekker, New York, 1977. 

Related Topics I Charge-Transfer Complexes in Biological Systems... 

III. EXAMPLES OF CHARGE-TRANSFER COMPLEXES IN BIOLOGICAL SYSTEMS... 

Despite intense study of the chemical reactivity of the inorganic NO donor SNP with a number of electrophiles and nucleophiles (in particular thiols), the mechanism of NO release from this drug also remains incompletely understood. In biological systems, both enzymatic and non-enzymatic pathways appear to be involved [28]. Nitric oxide release is thought to be preceded by a one-electron reduction step followed by release of cyanide, and an inner-sphere charge transfer reaction between the ni-trosonium ion (NO+) and the ferrous iron (Fe2+). Upon addition of SNP to tissues, formation of iron nitrosyl complexes, which are in equilibrium with S-nitrosothiols, has been observed. A membrane-bound enzyme may be involved in the generation of NO from SNP in vascular tissue [35], but the exact nature of this reducing activity is unknown. 

The several theoretical and/or simulation methods developed for modelling the solvation phenomena can be applied to the treatment of solvent effects on chemical reactivity. A variety of systems - ranging from small molecules to very large ones, such as biomolecules [236-238], biological membranes [239] and polymers [240] -and problems - mechanism of organic reactions [25, 79, 223, 241-247], chemical reactions in supercritical fluids [216, 248-250], ultrafast spectroscopy [251-255], electrochemical processes [256, 257], proton transfer [74, 75, 231], electron transfer [76, 77, 104, 258-261], charge transfer reactions and complexes [262-264], molecular and ionic spectra and excited states [24, 265-268], solvent-induced polarizability [221, 269], reaction dynamics [28, 78, 270-276], isomerization [110, 277-279], tautomeric equilibrium [280-282], conformational changes [283], dissociation reactions [199, 200, 227], stability [284] - have been treated by these techniques. Some of these... 

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