Vitamin molecules

The complexity of the vitamin molecule makes it extremely unlikely that total synthesis will ever be employed for preparation of commercial... 

The remaining molecules, vitamin C, pantothenic acid, and pyridoxamine, have comparatively large numbers of O—H and N—H groups. These groups allow each of these vitamin molecules to form many hydrogen bonds, so they are all water-soluble (all the B vitamins are soluble in water). 

Like ethinyloestradiol many other phenols exhibit fluorescence and as is the case for ethinyloestradiol, this fluorescence is pH dependent and does not occur under alkaline conditions when the phenolic group becomes ionised. Table 7.1 shows some examples of fluorescent drug and vitamin molecules. 

Biotin is a small vitamin molecule (Mr 244) that binds with highaffinity (kD 10 I5M I) to avidin. Avidin is a larger glycoprotein molecule (Mr 70,000), mostly distributed in egg whites. This protein has the advantage of conjugating with different markers, including peroxidase, fluorescent dyes, colloidal gold, and ferritin. Because of this property it is... 

Answer The properties of the vitamin—like any other compound—are determined by its chemical structure. Because vitamin molecules from the two sources are structurally identical, their properties are identical, and no organism can distinguish between them. If different vitamin preparations contain different impurities, the biological effects of the mixtures may vary with the source. The ascorbic acid in such preparations, however, is identical. 

Previously we studied the adsorption of vitamins Bh B6 and PP on unmodified and silylated silica. These data show that the affinity of adsorbates to the surface of modified silica is probably increased due to dispersive interactions between grafted groups and hydrocarbon fragments of vitamin molecules, as well as hydrophobic interactions. As a consequence, vitamin desorption into physiological solution or water slows down which, in turn, prolongs the action of the nanocomposite. 

Radioactive cobalt-60 is used to study defects in vitamin B12 absorption because cobalt is the metallic atom at the center of the vitamin molecule. The nuclear synthesis of this cobalt isotope involves a three-step process. The overall reaction is iron-58 reacting with two neutrons to produce cobalt-60 along with the emission of another particle. What particle is emitted in this nuclear synthesis What is the binding energy in J per nucleon for the cobalt-60 nucleus (atomic masses Co = 59.9338 amu ... 

Feedback repression is the inhibition of formation of one or more enzymes in a pathway by a derivative of the end product. In many (but not all) amino acid biosynthetic pathways, the amino add end product must first combine with its transfer RNA (tRNA) before it can cause repression. Feedback repression is a widespread regulatory device especially for the synthesis of molecules intended for incorporation into macromolecules, e.g. amino adds, purines, and pyrimidines. Synthesis of vitamins also appears to be controlled by feedback repression, as well as by catabolite regulation (Birnbaum et al, 1967 Sasaki, 1965 Newell and Tucker, 1966 Wilson and Pardee, 1962 Papiska and Lichstein, 1968). Regulation of vitamin synthesis is important since only a small number (probably about 1000) of vitamin molecules are required per cell whereas many molecules of an average amino acid (probably 50 million) are required. An extremely wasteful case of vitamin overproduction would develop if enzymes for vitamin synthesis were produced at the same rate and were as active as the amino acid biosynthetic enzymes. 

What do the chemical structures of vitamin molecules look like ... 

Above are the structures of some common vitamin molecules. They typically have a molecular weight in the neighborhood of 100-1500 g/mol. 

The identification of fragment B of the vitamin molecule gave less trouble. It was recognized as a thiazole derivative by Clarke and Gurin . On oxidation with nitric acid it yielded 4-methylthiazole-5-carboxylic acid (VI), a compound that had already been synthesized in 1890. It appeared to contain an aliphatic hydroxyl group which could be replaced by chlorine without much change in the U.V. absorption spectrum, so it could be reconstructed as having structure VII. 

Enzymes destroying thiamine have been encountered in some species in a number of fresh-water fish, in very few salt-water fish, in some shellfish and Crustacea, in bracken ferns and in three species of intestinal bacteria. They have all received the name of "thiaminase , but it is very probable that we have to do with several, different, enzymes >23 They all bring about a fission of the thiamine molecule, liberating the thiazole part, but only in one case, that of thiaminase of Bacillus aneurinolyticus Kimura el Aoyana, reasonable proof has been obtained of a hydrolytic fission, yielding both moieties of the vitamin molecule z-methyl-q-amino-S-hydroxymethylpyr-imidine and 4-methyl-5(/ -hydroxy)-ethylthiazole. 

It is possible to introduce some changes in the vitamin molecule and still retain vitamin activity. For instance, when the methyl group in position 2 on the pyrimidine ring is replaced by ethyl, the product stiU exhibits activity, albeit much reduced. The corresponding propyl derivative is inactive the butyl derivative has antithiamine properties, and so have 2-alkylthio derivatives. 

Randaccio, L., Geremia, S., Demitri, N., Wuerges, J. 2010. Vitamin B12 Unique metalor-ganic compounds and the most complex vitamins. Molecules, 15, 3228—59. 

A detailed discussion of fluorescence quenching, fluorescence, and other non-destructive TLC detection methods such as the use of reagents giving reversible color reactions and various biological methods was published by Barrett (1974). Although visualization with UV light is nondestructive with most substances and, therefore, well suited for preparative purposes, rearrangement of structure can sometimes occur—for example, with some steroid and vitamin molecules. 

This element is an essential constituent of vitamin B-12 and must be ingested in the form of the vitamin molecule inasmuch as humans synthesize little of the vitamin. No other function of cobalt has been established. 

Administration of the [ C]urogen isomer mixture afforded a vitamin molecule, the FT n.m.r. spectrum of whidi again showed the same set of four enhanced methylene signals. These results established that the biosynthetic route to Bij is... 

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