Glycine complex

Figure 3.4. TJV-vis absorption spectra of 3.10c in water and in water containing 3.0 mM of Cu (glycine) complex, 3.0 mM of Cu(N-methyl-Ftyrosine) and 3.0 mM of Cu(L-abrine).

Cu" amino-acid complexes Cu"-N-salicylidene-glycine complex CuCl3(guanine)H20]2 Cu(N-Pr"salen)2]... 

In contrast to the numerous tri-iron complexes in the preceding section, the bis(2-pyridylmethyl)-glycine complex [Fe3(02CMe)3(bpmg)3] has a space at the center of the Fe3 triangle. This can... 

Fig. 11. The slowly hydrolyzed substrate glycyl-L-tyrosine binds to carboxypeptidase A in a nonproductive complex where the amino-terminal glycine complexes the active-site ion (large sphere) to form a five-membered chelate, as in Fig. 10. Protein-bound zinc ligands Glu-72, His-69, and His-196 complete the coordinadon polyhedron of pentacoordinate zinc. Active-site residues are indicated by one-letter abbreviadons and sequence numbers E, glutamate H, hisddine R, arginine Y, tyrosine. [Reprinted with permission from Christianson, D. W., Lipscomb, W. N. (1986) Proc. Natl. Acad. Sci. U.S.A. 83,7568-7572.]...

Thus, it is only in an intermediate pH range that both functional groups can coexist in active form. This type of pH dependence has also been observed for other enzyme reactions and explained in similar terms (Laidler, 34). In this connection, the pH dependence of the catalytic activity of cupric glycinate complexes, discussed earlier (Fig. 2) should also be recalled. 

It has also been shown that the o -methylene group in chelated glycine will undergo substitution. The reaction of the copper (II)-glycine complex with ketones or aldehydes produces / -hydroxyamino acids (Equation 27) (1, 65). 

Amino acid complexes are also nucleophilic towards the Vilsmeier reagent. The cobalt(II) glycine complex (36) gives rise initially to an unusually stable iminium complex, which can be hydrolyzed with concentrated sulfuric acid to the complex of formylglycine (Scheme 13). The formyl group... 

Tracer studies139 using I80 have established that the two main pathways to the chelated glycine complex (which is not the sole product) are (a) internal nucleophilic attack by bound hydroxide ion on the N-coordinated ester and (b) attack of external hydroxide on the chelated ester. 

Whereas the VO24 ion forms only a 1 2 complex with L-lysine,414 there is evidence for both 1 1 and 1 2 complexes with glycine415 and with IVN -dihydroxyethyl-glycine.416 In the 1 1 glycine complexes, the amino-acid can function as a unidentate... 

Gutowski M, Dqbkowska I, Rak J, Xu S, Nilles JM, Radisic D, Bowen Jr. KH (2002). Barrier-free intermolecular proton transfer in die uracil-glycine complex induced by excess electron attachment. Eur Phys J D 20 431 139. 

Both dipolar and contact contributions are important in glycinate complexes. (166) U(iv) complexes with a-alanine, (167) various amino-acids, (168) ethyl trifluoroacetoacetate, (169) tetrakis-(tetra-ethylammonium)octathiocyanatouranate U(NCS)g(NEt4)4, (170) and -diketones (171, 172) have been examined. In studying the ligand exchange kinetics of the latter complexes (172) the mechanism is considered to involve a ninth coordination site in the U(iv) chelate. 

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