Metal complexes biological systems

Since the interpretation of NMR parameters in complex biological systems is considerably facilitated by the use of model compounds it is evident that a proper understanding of the metal-ligand interactions in the synthetic counterparts of vitamin B12, which are the subject of this review, can yield additional details and help clarify the role of corrinoids in Nature. 

Eric M. Shepard was born in 1977. He received a BS degree in chemistry from Rocky Mountain College. He studied copper- and TPQjContaining amine oxidases under Dr. David M. Dooley at Montana State University, where he was supported by an NSF IGERT fellowship on complex biological systems. He received his Ph.D. degree in biochemistry from MSU and is currently a postdoctoral research associate under Dr. Joan B. Broderick. His research interests are metal cluster assembly in the [FeFe] hydrogenase system and [Fe-S] cluster spectroscopy and reactivity. 

I would suggest that the formation of metal chelate complexes, with a four or six-coordinate metal partly bound to an optically active protein and partly bound to a substrate molecule can explain this stereospecificity. The optically active coordination compounds of metals, such as cobalt, have extraordinarily high molecular rotation, and so the difference in chelation powers of the d and I forms of a substrate may be very great. As Dr. Chaberek has pointed out (Lecture 33), this chelation may involve both metals of constant valency, e.g.. Mg, Zn, and those of variable valency. Metallic ions of both types are proven essential trace metals in biological systems. 

Figure 15-1. Examples of metal complexes and metals in biological systems.

Interest in the coordination chemistry of metal-sulfur complexes arises fixim their potential relevance to active sites in metalloenzymes and also from their ability to adopt various nuclearities and significant structural complexity [57-59]. In addition, interaction of toxic main group metals with biological systems frequently involves bonding to enzymes... 

The electron transfer rates in biological systems differ from those between small transition metal complexes in solution because the electron transfer is generally long-range, often greater than 10 A [1]. For long-range transfer (the nonadiabatic limit), the rate constant is... 

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