Cobalt, in vitamin

Benzimidazole is an important heterocyclic nucleus in the field of medicinal chemistry. The most prominent benzimidazole compound in nature is N-ribosyldimethylbenzimidazole, which serves as an axial ligand for cobalt in vitamin B12. The versatile nature of benzimidazole makes it a highly explored molecule in medicinal chemistry. A number of pharmacological activities are associated with benzimidazole derivatives such as anthelmintic, antiulcer, antipsychotic, proton pump inhibitor, antianxiety, anti-emetic and sedative, vasodilator, anticancer, analgesic, antihistaminic, antifungal, antiviral and antimicrobial. 

There are more complex examples of metal ion catalysis. Cobalt in vitamin B12 reactions forms covalent bonds with carbons of substrates.41,42 Metals can also act as electron conduits in redox reactions. For example, in cytochrome c the iron in the heme is reversibly oxidized and reduced. 

Para-aminobenzoic acid is destroyed on irradiation in aqueous solution by deamination and decarboxylation. Sulfanilamide and sulfathiazole are inactivated presumably because of deamination. The cobalt in vitamin B12 is reduced on irradiation from - -3 to the +2 state. 

Magnesium is almost equally present inside and outside the cells of our bodies. Actually, every element in the body, excepting perhaps the cobalt in vitamin B12, has multiple tasks and relationships to work out, and magnesium is no exception. I... 

The thiocyanate method has been used for determining cobalt in vitamin B12 [94], steel [24,94], and nickel [25]. Cobalt present in considerable amounts in alloys with aluminium, nickel, chromium, manganese, copper, and iron was determined by the differential spectrophotometric analysis [95]. 

A method for the determination of vitamin BJ2 by means of the luminol-hydrogen peroxide system has been developed. The method depends on the release of bound cobalt in vitamin B12 by acidification of the vitamin. The cobalt so released is then permitted to quantitatively catalyze the oxidation of luminol by hydrogen peroxide. 

Pratt, J. M. Cobalt in vitamin B12 and its enzymes, in Handbook on MetaUoprotdns, I. Bertini, A. Sigel,... 

Neutron activation analysis has also been employed sporadically for the determination of trace elements in protein fractions, collagen, nucleic acids as well as in biochemicals containing activatable elements (e.g., cobalt in vitamin B12 or selenium in selenoaminoacids). 

The number of protons identifies an element. Some elements may have atoms that contain different numbers of neutrons. The different atoms of the same element are then called isotopes. Because of the different number of neutrons in one isotope of an element, it can be quite radioactive that is, the nucleus is progressively breaking apart and giving off radiation. The type and amount of radiation determines the degree of risk. The radiation from isotopes is used in controlled situations - for example, cobalt therapy, for treating cancer. Cobalt 60 therapy uses a cobalt isotope with 33 neutrons. Normal cobalt in vitamin B12 or soil fertihzer almost alw s contains only 32 neutrons. Your home smoke detector may contain a 37kBq source of americium 241. Some natural elements, e.g. chlorine, are a mixture of two long-lived isotopes of the element. 

Cobalt compounds have been in use for centuries, notably as pigments ( cobalt blue ) in glass and porcelain (a double silicate of cobalt and potassium) the metal itself has been produced on an industrial scale only during the twentieth century. Cobalt is relatively uncommon but widely distributed it occurs biologically in vitamin B12 (a complex of cobalt(III) in which the cobalt is bonded octahedrally to nitrogen atoms and the carbon atom of a CN group). In its ores, it is usually in combination with sulphur or arsenic, and other metals, notably copper and silver, are often present. Extraction is carried out by a process essentially similar to that used for iron, but is complicate because of the need to remove arsenic and other metals. 

The compounds of the t/block elements show a wide range of interesting properties. Some are vital to life. Iron is an essential component of mammalian blood. Compounds of cobalt, molybdenum, and zinc are found in vitamins and essential enzymes. Other compounds simply make life more interesting and colorful. The beautiful color of cobalt blue glass, the brilliant greens and blues of kiln-baked pottery, and many pigments used by artists make use of d-block compounds. 

C03-0139. Vitamin B12 is a large molecule called cobalamin. There is one atom of cobalt in each molecule of vitamin B12, and the mass percentage of cobalt is 4.34%. Calculate the molar mass of cobalamin. 

Cobalt is present in animals in vitamin B12 (cyanocobalamine) and thus is essential for humans (Thunus and Lejeune 1994). The determination of Co has little significance for the diagnosis of deficiency of cyanocobalamine. Instead, cyanocobalamine itself must be determined in serum. The determination of methyl malonic acid in urine seems more reliable (McCann et al. 1996). 

From this sort of data it can be concluded that the cobalt(III) ion in this complex is a soft, or class b, Lewis acid. It has been suggested previously that the cobalt(III) ion in vitamin B12 was also a class b acid (138). The kinetic order, which presumably corresponds closely to the order of thermodynamic stability, suggests that for at least some ligands jr-bonding may be important. In this connection it is noteworthy that methylcobaloxime forms a complex with CO (139). 

A component of the ribotide reductase complex of enzymes, protein Ba, has been shown to contain two non-heme iron atoms per mole (77). This enzyme plays a vital, albeit indirect, role in the synthesis of DNA. Curiously, the lactic acid bacteria do not employ iron for the reduction of the 2 hydroxyl group of ribonucleotides. In these organisms this role has been assumed by the cobalt-containing vitamin Bi2 coenzyme (18). The mechanism of the reaction has been studied and has been shown to procede with retention of configuration (19). 

Another illustrative example is that of the Co(II) ion in vitamin B12 (cyanocoba-lamin) given in Figure 5.6. The cobalt is coordinated by four nitrogen atoms from... 

One of the most unusual features of the vitamin B12 structure is that cobalt is bonded directly to carbon. In heme, iron is bonded to five nitrogen atoms, but the sixth position is vacant until oxygen attaches. In vitamin B12, the sixth position is that bonded to the group indicated by R in the structure... 

Cobalt is an essential element for animals but not for plants, found in vitamin B12 and is utilized by micro-organisms. Vitamin B12, in common with a range of other organic substances can be taken up passively by plants. Plants products can therefore, contain considerable quantities of vitamin B12 although it is not essential for normal plant development (Mozafar 1994 Lundegardh and Martensson 2003). 

Naturally occurring compounds incorporating haem include vitamin Bi2, haemoglobin, and chlorophyll The central metal is iron in haemoglobin, magnesium in chlorophyll and cobalt in Bi2. 

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