Bioorganometallic chemistry

All the systems described in this chapter are organometallic in character. Coenzyme has several forms with M—C or M—H bonds. In nitrogen fixation, CO binds competitively at the active site. The nickel enzymes are believed to operate via intermediates with M—H (H2ase) or M—C bonds (CODH and MeCoM reductase). 

One of the important features of the chemistry of life is that biochemical reactions have to be kept under strict control. They must only happen as they are required, where they are required. One way of doing this is to employ 

Certain R groups are greasy and will tend to be found in the interior of the structure. Others are hydrophilic and are likely to be found at the surface. 

Metalloenzymes More than half of all enzymes have metal ions in their structure these are called metalloenzymes. In most cases, the metals are 

FIGURE 16.1 An enzyme lowers the activation energy for a reaction, often by binding the transition state (TS) for the reaction more tightly than the substrate (S) or product (P). The binding energy for the TS is represented as a in the figure. 

Iron-sulfur clusters, such as those found in the enzyme aconitase discussed in Section 7.9.2.1, cannot be treated using the 16-e or 18-e rules. Other frameworks exist to treat large metal clusters, and these have some utility in treating [Fe,cSj,] clusters. One method treats the number of metal atoms and the metal-metal bonds in a cluster according to the following formula  

For biological systems such as ferredoxins, problems arise when counting electrons by the valence electron method. This system assumes six Fe-Fe bonds within the tetrahedral iron-sulfur clusters, but Fe-Fe bond distances within biological iron-sulfur clusters, as found by X-ray crystallography, often 

Nature sometimes uses organometallic chemistry, but much less often than she uses coordination chemistry. 

The Organometallic Chemisiry cf the TransitUm Metals, Fourth Edition, by Robert H. Crabtree Coi right 2005 John Wiley Sons, Inc. 

One of the most important features of the chemistry of life is that biochemical reactions have to be kept under strict control. They must only happen as they are required, where they are required. One way of doing this is to employ reactions that can only proceed when catalyzed. The organism now only has to turn the appropriate catalysts on and off to control its biochemistry. The catalysts of biology are called enzymes, and they can be soluble, or bound to a membrane, or even part of an enzyme complex, in which case they act as a cog in a larger piece of biochemical machinery. 

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One large class of non-heme iron-containing biomolecules involves proteins and enzymes containing iron-sulfur clusters. Iron-sulfur clusters are described in Sections 1.7 (Bioorganometallic Chemistry) and 1.8 (Electron Transfer) as well as in Section 3.6 (Mossbauer Spectroscopy). See especially Table 3.2 and the descriptive examples discussed in Section 3.6.4. Iron-sulfur proteins include rubredoxins, ferrodoxins, and the enzymes aconitase and nitrogenase. The nitrogenase enzyme was the subject of Chapter 6 in the hrst edition of this text—see especially Section 6.3 for a discussion of iron-sulfur clusters. In this... 

Linear polarization, and NLO properties, 12, 102 Linear polymers, siloxanes, synthesis, 3, 660 Linkage isomerism, for photochromic behavior, 1, 245 Linked cages, metallacarboranes, 3, 245 Linkers, traceless, chromium carbonyls as, 5, 251 Lipids, in bioorganometallic chemistry, 1, 904 Liquefied noble gases, in low-temperature infrared studies, 1, 264... 

Molecular recognition, in Rh Cp complexes, 7, 155 Molecular weight, in alkene living polymerizations, 11, 715 Moller-Plesset calculations, as perturbation method, 1, 646 Molten salts, and ionic liquids, 1, 848 Molybdacarboranes, synthesis, 3, 216 Molybdenocene dichloride, bioorganometallic chemistry,... 

Fish RH, Jaouen G (2003) Bioorganometallic chemistry structural diversity of organometallic complexes with bioligands and molecular recognition studies of several supramolecu-lar hosts with biomolecules, alkali-metal ions, and organometallic pharmaceuticals. Organometallics 22 2166-2177... 

Lo HC, Leiva C, Buriez O, Kerr JB, Olmstead MM, Fish RH (2001) Bioorganometallic chemistry. 13. Regioselective reduction of NAD+ models, 1-benzylnicotinamide triflate and P-nicotinamide ribose-5 -methyl phosphate, with in situ generated [CpRh(Bpy)H]+ structure-activity relationships, kinetics, and mechanistic aspects in the formation of the 1,4-NADH derivatives. Inorg Chem 40 6705-6716... 

Keywords Bioorganometallic chemistry Cancer chemotherapy Mode of action Organometallic compounds Protein binding Targeted drugs... 

Hartinger CG, Dyson PJ (2009) Bioorganometallic chemistry - from teaching paradigms to medicinal applications. Chem Soc Rev 38 391-401... 

Van Staveren DR, Metzler-Nolte N (2004) Bioorganometallic chemistry of ferrocene. Chem Rev 104 5931-5986... 

Metzler-Nolte N, Salmain M (2008) The bioorganometallic chemistry of ferrocene. In Stepnicka P (ed) Ferrocenes ligands, materials and biomolecules. Wiley, Chicester, pp 499-639... 

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