Tyrosine complexes

This part of the photosynthetic chain can be mimicked by ruthenium-tyrosinate and manganese-tyrosinate complexes [80-82], In the excited state the ruthenium-polypyridine complex abstracts one electron from the tyrosinate moiety, yielding... 

The effect of acetonitrile on the kinetics of oxidation of ascorbic acid by Cu(II) and the ferrocenium ion in aqueous acetonitrile has been studied, as has the similar oxidation using the Cu(II)-tyrosine complex, for which a mechanism has been proposed. A reinvestigation of the oxidation of ascorbic acid by Fe(III) has shown catalysis by even small amounts of added chloride, 7 and the kinetics and mechanism of the oxidation of ascorbate by manganese pyrophosphate have been studied. The heat stability of aqueous solutions of ascorbic acid is increased witli reduced o gen concentrations, with Cu(II) and Fe(II) accelerating decomposition. ... 

Similarly, the oxidation of Fe " during iron core formation in recombinant human H subunit ferritin and its variants has been investigated by stopped-ftow kinetics and Mossbauer spectroscopy [494]. An intermediate species, attributed to the purple Fe -Tyr34 complex in the Fe2 site, was shown to form rapidly ( ox 1000 s ) and to decay within the first 5-10 s. This Fe -tyrosinate complex was shown to form following the rapid uptake and oxidation of Fe, and was proposed as one of the initial steps in the fast mineralization process [474]. The oxidation of Fe has been shown to lead to the formation of various species, including Fe " " monomers, dimers, and some larger clusters. Specifically, the observed fast oxida-... 

Waldo GS, Ling JS, Sanders-Loehr J, Theil EC. 1993. Formation of an Fe(III)-tyrosinate complex during biomineralization of H-subunit ferritin. Science 259 796-798. 

As suggested by Lerner (1953) the Cu++ enzyme would undergo cyclic valency change. First an enzyme-Cu+-tyrosine complex khould be formed, reacting with oxygen afterwards. We have suggested already (Massart and Vercauteren, 1959) that the reaction mechanism within the complex might be ... 

Crystal stmctures of complexes of copper(II) with aromatic amine ligands and -amino acids " " and dipeptides" have been published. The stmctures of mixed ligand-copper complexes of L-tryptophan in combination with 1,10-phenanthroline and 2,2 -bipyridine and L-tyrosine in combination with 2,2 -bipyridine are shown in Figure 3.2. Note the subtle difference between the orientation of the indole ring in the two 1,10-phenanthroline complexes. The distance between the two... 

A method that has been the standard of choice for many years is the Lowry procedure. This method uses Cn ions along with Folin-Ciocalteau reagent, a combination of phosphomolybdic and phosphotnngstic acid complexes that react with Cn. Cn is generated from Cn by readily oxidizable protein components, such as cysteine or the phenols and indoles of tyrosine and tryptophan. Although the precise chemistry of the Lowry method remains uncertain, the Cn reaction with the Folin reagent gives intensely colored products measurable spectrophotometrically. 

Tyrosine phosphorylated IRS interacts with and activates PI 3-kinase [3]. Binding takes place via the SRC homology 2 (SH2) domain of the PI 3-kinase regulatory subunit. The resulting complex consisting of INSR, IRS, and PI 3-kinase facilitates interaction of the activated PI 3-kinase catalytic subunit with the phospholipid substrates in the plasma membrane. Generation of PI 3-phosphates in the plasma membrane reemits phospholipid dependent kinases (PDKl and PDK2) which subsequently phosphorylate and activate the serine/threonine kinase Akt (synonym protein... 

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