Zinc

The metal zinc is known as a metallic chemical element that is found in reasonable abundance around the world. It is classified in the transition metals, along with nickel and mercury. This metal is used in various alloys and compounds which have a variety of uses from sunscreen to fine art. In addition to this, living organisms also rely on zinc as a valuable nutritional trace element. This metal is hard and brittle at most temperatures and is a fair conductor of electricity. With this in mind, zinc is the second most abundant trace element in the body and as a deficiency it can have serious effects on normal bodily physiology. These effects include: abnormal development, movement disorders, and anorexia. Zinc is found mostly in the strong muscles of the body; especially in high concentrations in red and white blood cells, eye retina, skin, liver, kidneys, bones, and pancreas.
Zinc is an essential trace element that is vital for growth and development. It is instrumental in the immune response, brain function, and the ability to reproduce. This metal is essential for the proper function of cellular metabolism. About one hundred enzyme rely on this metal to help them in catalyzing vital chemical reactions. Zinc helps in protecting cell membranes from oxidative damage and helps stabilize the structure of the cell proteins. The zinc proteins bind to DNA which help the genes tell the cells in what to do; which include: telling certain cells to die, which is essential for growth, gestation, and disease prevention. It also helps with the control of releasing the hormones and the transmission of nerve impulses.

References:
1. Metals in medicine and the environment. The role of zinc in ischemia. 05 August 2009. 31 March 2011. <http://www.faculty.virginia.edu/metals/cases/corson2.html>.
2. Nionomya, Kent. What does zinc do for the body. 02 February 2011. 31 March 2011. <http://www.ehow.com/about_4678519_zinc-do-body_.html>.
3. Health benefits of zinc. Organic Facts. 31 March 2011. <http://www.organicfacts.net/health-benefits/minerals/health-benefits-of-zinc.html>.

Fe-Only Hydrogenase

Hydrogenase is defined as: "catalyzing the reversible oxidation of molecular hydrogen (H2) and playing a vital role in anaerobic metabolism." The standard catalyzed reaction is H2----> 2H + 2e- Metal containing hydrogenases is divided into three families (Fe hydrogenase, Ni-Fe hydrogenase, and Ni-Fe-Se hydrogenase). If the hydrogenase contains no other metal than Fe they are called the Fe only hydrogenase which contains two families within. The first one is cytoplasmic, soluble, monomeric Fe Hases, and they are found in strict anaerobes such as: Clostriduim pasteruranium and Megasphaera elsdenii. They are extremely sensitive to inactivation by O2 and catalyse both hydrogen evolution and hydrogen uptake. The second group is periplasmic, heterodimeric Fe-Hases from Desulfovibrio which can be purified aerobically and catalyse mainly by H2 oxidation.
These enzymes contain high field ligands such as: cyano and CO (metal carbonyl) which are located in the first coordination sphere of the cluster. Since the cyano and carbonyl ligands are toxic to many biological systems their inclusion in this system play pivotal roles. The high field ligands help ensure that the iron center at the active site remain in a low spin state throughout the catalytic cycle. When the enzyme is isolated in the air a observed oxidized inactive state takes place. However, when the Fe Hydrogenase is fully reduced calculations can show that different oxidation states of the two subunit takes place during the catalytic H2 evolution. Pretty much it should be a Fe(II)-Fe(II) complex with a hydroxyl group (OH) group bonded. Due to the fact that they have high field ligands I would assume that these enzymes would also contain a strong field.

References:
1. Hydrogenase. Wikipedia. 28 February 2011. <http://en.wikipedia.org/wiki/Hydrogenase>.
2. Iron Hydrogenase. 1 February 1999. 28 February 2011. <http://metallo.scripps.edu/PROMISE/FEHASE.html>.
3. Role of Fe hydrogenase in biological hydrogen production. Current Science Vol. 90 No. 12. 25 June 2006. 3 March 2011. <http://www.scribd.com/doc/10453075/Role-of-FeHydrogenase-in-Biological-Hydrogen-Production>.

Biomineralization

Biomineralization is defined as: the process by which living organisms produce minerals which can harden or stiffen existing tissues. Biominerals perform a variety of roles in organisms, with the most important being support, defence and feeding. With knowing this the metal that I chose was zinc. Zinc is consider to be a common element in nucleic-acid polymerases and transcription factors, where it's role is consider to be structural instead of catalytic and can help enhance the stereoselctivity of the polymerization of nucletiodes under reaction conditions. With this in mind, a group of nucleic-acid binding proteins with a repeated sequence containing the amino acids cysteine and histidine, were shown to bind as many as eleven zinc atoms which were necessary for protein function. Zinc plays numerous aspects in the role of cellular metabolism,  the immune function, protein synthesis, wound healing, DNA synthesis, and cell disvion. This metal is essential for animals and plants since the metal ion can uptake into the roots of plants which helps in the flow of the soil solution. Zinc is used in humans to build molecules of DNA, and directs the reproduction. Furthermore, the metal is used in galvanizing (process of laying down other a thin layer of zinc on the surface of a second metal). The reason for this is because zinc does not corrode as easily as iron so therefore it can protect iron and other metals from corrosion. An important use of zinc is with alloys. An alloy is made by melting and mixing two or more metals. The mixture has different properties from those of the individual metal; so two of the most common alloys are brass and bronze. With brass being an alloy of zinc and copper and bronze being an alloy of copper and tin but containing a small trace of zinc. The alloys of zinc are used in a variety of things such as: automobile parts, roofing, gutters, batteries, and building materials.
Pictures are shown below:

zinc found on plants

crystals of zinc