Vitamins spectra

Fia, 3. Infrared absorption spectra of the K vitamins. Spectrum 1 vitamin (oil) spectrum 2 tamin Kt(io) (molten) spectrum 3 vitamin Kt(io> (crystalline) spectrum 4 vitamin Ksctt) (crystalline). 

Determination of structural features. The ultraviolet spectrum has been of value in the determination of the structure of several vitamins. Thus the presence of an a-naphthoquinone system in vitamin K was first detected by this means. Also the 4-methylthiazole and the 2 5-dimethyl-6-aminopyridine system was first identified in vitamin Bj (thiamine), a- and /3-Ionones can be distinguished since the former contains two conjugated chromophores and the latter three conjugated chromophores. 

The ultraviolet spectrum of vitamin Be, or pyridoxine, measured in aqueous ethanol varies with the composition of the solvent indicating that this compound is in equilibrium with the zwitterion form 38. The equilibrium constant in pure water was obtained by extrapolation. Prior to this, equilibria which involved tautomers of type 39 had been suggested for vitamin Be, but see Section VI,A. In the case of pyridoxal, an additional equilibrium, 40 41, occurs (cf. Section VIII) other pyridoxal analogs have also been studied (Table II). 

High-pressure pumps operating at up to 6000 psi are required to force solvent through a tightly packed HPLC column, and electronic detectors are used to monitor the appearance of material eluting from the column. Alternatively, the column can be interfaced to a mass spectrometer to determine the mass spectrum of every substance as it elutes. Figure 12.18 shows the results of HPLC analysis of a mixture of 10 fat-soluble vitamins on 5 jam silica spheres with acetonitrile as solvent. 

Also, the outcome covers a large spectrum. Autoantibodies can specifically block an important protein (such as the gastric intrinsic factor required for the uptake of orally taken vitamin B12), or the receptor for —> acetylcholine (as in myasthenia gravis), but also can... 

This procedure illustrates a broadly applicable method which is essentially that of Roth, Dubs, Gotschi, and Eschenmoser,2 for the synthesis of enolizable /1-dicarbonyl compounds. Although there are various methods for the preparation of /3-dicarbonyl systems,3 the scheme of sulfide contraction widens the spectrum of available methods. The procedure can also be utilized in the synthesis of aza and diaza analogs of /3-dicarbonyl systems. Eschenmoser2 has utilized the method to produce vinylogous amides and amidines in connection with the total synthesis of corrins and vitamin B12.4... 

Natural pigment production for food coloration includes the entire spectrum of biotechnologies. For example, biological production of carotenoid pigments has medical implications because carotenoids are nutritive (pro-vitamin A), antioxidant, and photoprotective. Carotenoids are produced alternately in agricultural systems (plants), industrial bioreactors (bacterial and fungi), and marine systems (cyanobacteria and algae). 

Fluorescent probes are divided in two categories, i.e., intrinsic and extrinsic probes. Tryptophan is the most widely used intrinsic probe. The absorption spectrum, centered at 280 nm, displays two overlapping absorbance transitions. In contrast, the fluorescence emission spectrum is broad and is characterized by a large Stokes shift, which varies with the polarity of the environment. The fluorescence emission peak is at about 350 nm in water but the peak shifts to about 315 nm in nonpolar media, such as within the hydrophobic core of folded proteins. Vitamin A, located in milk fat globules, may be used as an intrinsic probe to follow, for example, the changes of triglyceride physical state as a function of temperature [20]. Extrinsic probes are used to characterize molecular events when intrinsic fluorophores are absent or are so numerous that the interpretation of the data becomes ambiguous. Extrinsic probes may also be used to obtain additional or complementary information from a specific macromolecular domain or from an oil water interface. 

Nitrogen ENDOR spectra of frozen solutions of the copper-containing analogue of vitamin BJ2 have been used to verify the corresponding EPR data obtained from powder simulations2331. The hf values from the very poorly resolved ENDOR spectra agree with the EPR results within experimental error. Since the errors estimated from the ENDOR spectra are only insignificantly smaller than those from the EPR powder spectrum, the ENDOR measurements will not alter the interpretation of the data. 

Surface-enhanced Raman scattering using a silver-coated alumina support selectively enhanced the spectrum of p-aminobenzoic acid. This allowed the determination of this compound at low ppm levels in vitamin B complex354,355. 

Prolonged treatment with broad-spectrum antibiotics (eUminate intestinal bacteria that supply vitamin K)... 

Vitamin B2, or riboflavin, is the metabolic precursor to two flavin coenzymes essential for the integrity of a spectrum of redox reactions. 

Primary vitamin K deficiency is uncommon, not only because of the presence of vitamin K in many plant and animal tissues but also due to its production by microorganisms in the intestine. Broad spectrum antibiotics, however, can lead to low levels of vitamin K due to loss of microorganisms in the intestine. Newborn infants can become deficient since it does not cross the placenta, hence... 

Fig. 5. Examples of GC-MS data for vitamin E in a vegetable oil and cattle feedlot soil (a) vegetable oil, sum of key ions mjz 129 (TMS for sterols), 474, 488 and 502 of tocopherols as TMS), (b) feedlot soil, sum of key ions ra/z 416 and 430 for tocopherols, a-tocopheryl acetate, and the metabolite (as free phenols), and (c) mass spectrum of a-tocopherol hydroquinone (V).

Persons with vitamin deficiency exhibit a spectrum of nonspecific neurologic manifestations, in-ciuding depression, confusion, and disorientation, which may lead to convulsions in severe cases. 

Hypoprothrombinemia may occur in malabsorption syndromes and also the use of broad-spectrum antibiotics may produce a hypoprothrombinemia that responds readily to small doses of vitamin K. In premature infants and in infants with hemorrhagic disease of the newborn the use of vitamin K may be indicated. However, the main indication for the use of vitamin K is to antagonize the anticoagulant activity of coumarins. Oral absorption of phytonadione and the menaquinones is by the lymph while menadione and its water-soluble derivatives are absorbed directly. The absorption of phytonadione is energy-dependent and saturable. Intravenous administration of phytonadione has produced flushing, dyspnea, chest pains, and cardiovascular collapse. 

The rd rd cl mouse has provided a powerful model to characterize the ocular non-rod, non-cone photoreceptors of mammals using action spectrum techniques. The first completed action spectrum was for the pupillary light reflex PLR (Lucas et al 2001). The results demonstrated that the PLR in rd rdcl mice is driven by a single opsin/vitamin A-based photopigment with a 479 nm. The... 

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