Zinc complexes biology

Imidazole is of particular relevance to biological mimic ligands due to the presence of histidine as a coordinating group for zinc in biological systems and has been a particular target for zinc complex formation. 

Hoshino Y, Mukai A, Yazawa K, Uno J, Ishikawa J, Ando A, Fukai T, Mikami Y (2004) Transvalencin A, a Thiazolidine Zinc Complex Antibiotic Produced by a Clinical Isolate of Nocardia transvalensis I. Taxonomy, Fermentation, Isolation and Biological Activities. J Antibiot 57 797... 

Aldolases such as fructose-1,6-bisphosphate aldolase (FBP-aldolase), a crucial enzyme in glycolysis, catalyze the formation of carbon-carbon bonds, a critical process for the synthesis of complex biological molecules. FBP-aldolase catalyzes the reversible condensation of dihydroxyacetone phosphate (DHAP) and glyceralde-hyde-3-phosphate (G3P) to form fructose-1,6-bisphosphate. There are two classes of aldolases the first, such as the mammalian FBP-aldolase, uses an active-site lysine to form a Schiff base, whereas the second class features an active-site zinc ion to perform the same reaction. Acetoacetate decarboxylase, an example of the second class, catalyzes the decarboxylation of /3-keto acids. A lysine residue is required for good activity of the enzyme the -amine of lysine activates the substrate carbonyl group by forming a Schiff base. 

Tripod ligands of the pyrazolyl/thioimidazolyl-borate offering N2S, NS2, and S3-donor sets were employed in the study of biologically relevant alkylations of the R-thiolate zinc complexes (R = ethyl-, benzyl-, phenyl-, and p-nitrophenyl).78 A review recently described the use of poly(mercaptoimidazolyl)-borate in the chelation of cadmium and mercury.107... 

As one of new methods, the fluorimetric determination of zinc in biological materials, beverages, and alloys has been described, using salicylaldehyde thiocarbazone as a complexing agent (Cano-Pavon et al. 1986). In particular, the new zinc-specific fluorophores have been developed to measure and visualize intracellular zinc (Coyle etal. 1998). 

The manifold important zinc-containing biological systems have spawned a multitude of model complexes,thereby greatly enriching knowledge of the coordination chemistry of zinc (see Sections 8 and 9). Types of model complexes include those with amino acid ligands to model zinc-peptide interactions, NNN-donor ligands to model the active site of carbonic anhydrase or carboxypeptidases, NO-donor Schiff bases to model Zn2 sites, and and polynuclear... 

The direct determination of zinc in diet, tissue and in body fluids can be accomplished by a variety of methods. A common limitation is the chance of sample contamination prior to analysis. Some early studies using less sensitive methods may not have recognised this problem and reported erroneously high results. Older colorimetric methods required that the biological sample be efficiently digested or otherwise deproteinised, prior to formation of a coloured zinc complex. These techniques have largely been superseded by atomic absorption spectrometry which is more sensitive yet less prone to interferences. For fluids such as plasma or urine, simple dilution is all that is required prior to analysis. Tissue or diet samples only require to be dissolved in mineral acid. These simpier sample preparation procedures limit the chances of contamination. 

Porphyrin, dihydro-metal complexes geochemistry, 862 Porphyrin, hydrometal complexes biology, 546 Porphyrin, tetrahydro-mctal complexes geochemistry, 862 Porphyrin, tetraphenyl-indium complexes radiopharmacology, 971 zinc... 

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