Selenomethionine synthesis

H NMR, 4, 1042 ionization potentials, 4, 1046 synthesis, 4, 1066 UV spectra, 4, 1044 Selenolo[2,3 -cjthiophenes H NMR, 4, 1042 synthesis, 4, 1067 UV spectra, 4, 1044 Selenolo[3,2-6]thiophenes dipole moments, 4, 1049 H NMR, 4, 1042 ionization potentials, 4, 1046 synthesis, 4, 1066 UV spectra, 4, 1044 Selenolo[3,4-6]thiophenes synthesis, 4, 1067 Selenolo[3,4-c]thiophenes addition reactions, 4, 1062 synthesis, 4, 1076 Selenomethionine applications, 4, 970 Selenophene, 3-acetamido-reactions, 4, 953 Selenophene, 2-acetyl-mercuration, 4, 946 nitration, 4, 947 Selenophene, 2-alkyl-reactions, 4, 45 synthesis, 4, 135, 967 Selenophene, 3-alkyl-synthesis, 4, 135, 967 Selenophene, 3-aryl-synthesis, 4, 963 Selenophene, 2-benzyl-reactivity, 4, 946 Selenophene, 2-benzyl-5-ethyl-reduction, 4, 950... 

Kigawa, T., Yamaguchi-Nunokawa, E., Kodama, K. et al. (2002) Selenomethionine incorporation into a protein by cell-free synthesis. Journal of Structural and Functional Genomics, 2 (1), 29-35. 

The constmction of synthetic selenocysteine-containing proteins or selenium-containing proteins attracts considerable interest at present, mainly for the reason that it can be used to solve the phase problem in X-ray crystallography. Selenomethionine incorporation has been used mostly uutil now for this purpose. There are also two reports ou uew synthetic selenocysteine-containing proteins. In one case, the active site serine of subtUisin has been converted into a selenocysteine residue by chemical means, with the result that the enzyme gains a predominant esterase instead of protease activity. In the second case, automated peptide synthesis was carried out to produce a peptide in which all seven-cysteine residues of the Neurospora crassa metallothioueiu (Cu) were replaced by selenocysteine. The replacement resulted iu au alteration of both the stoichiometry and the affinity of copper binding. ... 

Methionine and Vitamin E. Combinations of methionine and vitamin E have been found to be antagonistic to selenium toxicity. In one study, selenium concentrations in the liver and kidneys of rats fed selenium-containing diets with methionine and vitamin E were less than the concentrations found in the livers and kidneys of rats fed selenium with either methionine or vitamin E alone (Levander and Morris 1970). The results are compatible with the hypothesis that methionine detoxifies selenium by forming methylated derivatives of selenium that are eliminated in the urine and in expired air (see Section 3.4.4) or that methionine and selenomethionine are in the same pool of amino acids and that by increasing the amount of methionine relative to selenomethionine, the probability of selenomethionine being randomly inserted into proteins during synthesis decreases (Stadtman 1977,1980,1983,1987, 1990). As discussed in Section 3.11, methionine administered as an antidote for acute selenium toxicity in rats was ineffective (Lombeck et al. 1987). This result supports a mechanism of action involving protein synthesis rather than a methylation mechanism hypothesis. 

As an important example of a biochemically relevant species, Se-labeled selenomethionine can be prepared, for example, by isolation from selenized yeast, grown in a Se-labeled selenite solution. After digestion of the yeast with pro-tease/lipase solution, Se-labeled selenomethionine is isolated by size-exclusion chromatography (SEC) [72, 73]. Another important example is the synthesis of Fe-labeled transferrin [74]. The synthesis of other biologically relevant molecules, especially those of higher molecular weight, is usually too complicated, and the species-unspecific spiking mode is more convenient in these cases. 

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