Biomimetic models

Levanon H and Mobius K 1997 Advanced EPR spectroscopy on electron transfer processes in photosynthesis and biomimetic model systems Ann. Rev. Biophys. Biomol. Struct. 26 495-540... 

One-step hydroxylation of aromatic nucleus with nitrous oxide (N2O) is among recently discovered organic reactions. A high eflSciency of FeZSM-5 zeolites in this reaction relates to a pronounced biomimetic-type activity of iron complexes stabilized in ZSM-5 matrix. N2O decomposition on these complexes produces particular atomic oj gen form (a-oxygen), whose chemistry is similar to that performed by the active oxygen of enzyme monooxygenases. Room temperature oxidation reactions of a-oxygen as well as the data on the kinetic isotope effect and Moessbauer spectroscopy show FeZSM-5 zeolite to be a successfiil biomimetic model. 

Mahadevan V, Gebbink RJMK, Stack TDP. 2000. Biomimetic modeling of copper oxidase reactivity. Curr Opin Chem Biol 4 228-234. 

Conventional MS in the energy domain has contributed a lot to the understanding of the electronic ground state of iron centers in proteins and biomimetic models ([55], and references therein). However, the vibrational properties of these centers, which are thought to be related to their biological function, are much less studied. This is partly due to the fact that the vibrational states of the iron centers are masked by the vibrational states of the protein backbone and thus techniques such as Resonance Raman- or IR-spectroscopy do not provide a clear picture of the vibrational properties of these centers. A special feature of NIS is that it directly reveals the fraction of kinetic energy due to the Fe motion in a particular vibrational mode. 

Beer PD, Bayly SR (2005) Anion Sensing by Metal-Based Receptors. 255 125-162 Bertini L, Bruschi M, de Gioia L, Fantucci P, Greco C, Zampella G (2007) Quantum Chemical Investigations of Reaction Paths of Metalloenzymes and Biomimetic Models - The Hydrogenase Example. 268 1-46 Bier FF, see Heise C (2005) 261 1-25... 

The mechanistic and structural chemistry of B12 may be separated into (i) investigations of cobalamin cofactors both apart from and in complex with their enzymes, and (ii) biomimetic model complexes, both structural and functional. 

There are many biomimetic model Co complexes of the cobalamins.1149 The primary criterion for an effective B12 model has been that the complex may be reduced to the monovalent state and undergo facile oxidative addition to generate a stable alkylcobalt(III) complex. The two main classes of B12 model complexes that have been investigated are Co oximes and Schiff base complexes. The former class shares the planar CoN4 array of their biological analogs whereas the majority of effective Schiff base Bi2 model complexes comprise equatorial czj-N202 donor sets. 

Asymmetric reduction of ketones or aldehydes to chiral alcohols has received considerable attention. Methods to accomplish this include catalytic asymmetric hydrogenation, hydrosilylation, enzymatic reduction, reductions with biomimetic model systems, and chirally modified metal hydride and alkyl metal reagents. This chapter will be concerned with chiral aluminum-containing reducing re-... 

Ma Y, Balbuena PB (2007) Density functional theory approach for improving the catalytic activity of a biomimetic model based on the Fe-only hydrogenase active site. J Electroanal Chem (in press)... 

Porphyrin quinones serve as biomimetic models for fundamental studies on photo-induced ET. Most studies have been performed with the well-known porphyrin p-quinones and the isomeric porphyrin o-quinones have been mostly neglected due to their higher chemical reactivity but in fact they should be better electron acceptors. Speck et al. synthesized several porphyrin o-quinones and have shown that a facile and simple variation of AGEt can be achieved by using in situ formed semiquinones for metal chelation230. 

Biomimetic modelling of many zinc metalloenzymes has been the subject of much research which is well served with useful reviews (refs. 9, 10, 11, 16-22,1241a [pp. 35 et seq.]). 

The synthetic conditions are unsatisfactory with respect to the intended role of the reaction as a potentially biomimetic model, but demonstrate that it is possible to achieve interconversion between the structures of hydroporphyrin, secocorrin and corrin. 

Dithiocarbamates, in Ru and Os half-sandwiches, 6, 493 Dithiocarbenes, Pt complexes, 8, 439 Dithiocarboxy ligands, in molybdenum carbonyls, 5, 447 Dithiolate-bridged compounds in dinuclear iron compounds with Fe-Fe bonds, 6, 238 as iron-only hydrogenase biomimetic models, 6, 239 Dithiolate diamides, with Zr(IV), 4, 784 Dithiolene—uranium complexes, synthesis and characterization, 4, 212 Ditopic receptors, characteristics, 12, 489 Ditungsten complexes, associated reactions, 5, 748 Divinyllead diacetates... 

Iron-only hydrogenase, dithiolate-bridged compounds as biomimetic models, 6, 239 Iron oxide films, synthesis, 12, 51 Iron-palladium nanoparticles, preparation, 12, 74 Iron-platinum bimetallic clusters, with isocyanide clustes,... 

A large number of biomimetic Mn models have been prepared, and their spectroscopic and structural properties, which played an important role in linking OEC spectroscopic features to structural topologies, have been reviewed recently [9], Consequently, this review will be limited to synthetic biomimetic models that are directly catalytically relevant, i.e., that form, contain, or split 0—0 bonds. 

Among heteronuclear complexes, the binuclear compound 88 with the moiety Fe — C = N—Cu is interesting as a biomimetic model of cytochrome C-oxidaze [121] ... 

Among the coordination compounds obtained on the basis of polypyrazolyl-borates, it is worth emphasizing the copper chelates 235 which are still the only biomimetic model of blue copper proteins, reproducing all their physical (UV-and EPR-spectral) properties [441,446-448], Compound 236 [449] is also an example of complexes of this kind of system ... 

The main significance of the examined polycyclic ligands is in the creation of the basis of coordination chemistry for the -elements of Groups IA and IIA of the Periodic Table. Not long ago the above complexes of these elements were only represented by a few single examples at present, hundreds of them have been described. Another important aspect to be mentioned is the use of crown-ether complexes as biomimetic models of ionophores [579 581]. 

Additionally to nickel ICC, chelates of the types 467, 468, 472, and 473, containing either cobalt, iron, copper, palladium, zinc, cadmium, or mercury, have also been obtained [269,270,804]. Special interest amongst them is provoked by copper ICC containing an azomethinic N,S-ligand environment. These compounds are one of the several biomimetic models of nonporphyrine metal proteins [448,804,834]. The majority of these ICC have trimetallocyclic structures of the types shown by struc-... 

The problem of biomimetic model design simulating the action mechanism of corresponding enzymes is based on the idea of structural-functional conformity. In 1971, alcohol dehydrogenase was primarily synthesized [123], In this biomimetic system the product is formed due to direct electron transfer from the reduced co-factor (NADH) analog to aldehyde. Note that the display of alcohol dehydrogenase catalytic activity requires the presence of zinc (II) ion. 

It would seem that the use of synthetic organic polymers as a matrix in biomimetic models would lead to the creation of effective catalysts. Although an affinity between natural and synthetic macromolecular systems with catalytic groups added to them is sometimes observed, nevertheless, they were found less effective. 

Iron porphyrin dimers, iron(III) /a-oxodimcr iron(III) porphyrin, for example, are used as biomimetic models of oxidation catalysts [98], It is shown that [Fe(TFPP)]20 and other modifications regioselectively oxidize adamantane and cyclohexane in the presence of iodosylbenzene (PhIO). Comparison of these results with corresponding monomeric analogs indicates the efficiency of the FeP dimer at the level of the monomeric one. 

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