Alanine, complex with

Selectivity studies with DTU indicated marked discrimination in the clathrate formation 23,45). As in other types of clathrates, the steric factor is important in differentiation between compounds of similar functionality but different shape. For example, DTU forms crystalline complexes with some alcohols (methanol, ethanol, propanol, 1-butanol) but not with others (2-butanol). It complexes the ethyl esters of N-acetyl derivatives of glycine, alanine, methionine and aspartic acid, but not of proline, serine, phenylalanine and glutamic acid. 

Hall et at. 300) described an indirect method for the determination of urinary a-amino nitrogen. Copper is solubilized from insoluble copper phosphate by complexing with a-amino groups at slightly alkaline pH. The remaining copper phosphate is removed by filtration and the filtrate is diluted 1 10 or 1 20 with 0. IN hydrochloric acid to measure the dissolved copper by atomic absorption. Standards are prepared using alanine. 

One of the important consequences of studying catalysis by mutant enzymes in comparison with wild-type enzymes is the possibility of identifying residues involved in catalysis that are not apparent from crystal structure determinations. This has been usefully applied (Fersht et al., 1988) to the tyrosine activation step in tyrosine tRNA synthetase (47) and (49). The residues Lys-82, Arg-86, Lys-230 and Lys-233 were replaced by alanine. Each mutation was studied in turn, and comparison with the wild-type enzyme revealed that each mutant was substantially less effective in catalysing formation of tyrosyl adenylate. Kinetic studies showed that these residues interact with the transition state for formation of tyrosyl adenylate and pyrophosphate from tyrosine and ATP and have relatively minor effects on the binding of tyrosine and tyrosyl adenylate. However, the crystal structures of the tyrosine-enzyme complex (Brick and Blow, 1987) and tyrosyl adenylate complex (Rubin and Blow, 1981) show that the residues Lys-82 and Arg-86 are on one side of the substrate-binding site and Lys-230 and Lys-233 are on the opposite side. It would be concluded from the crystal structures that not all four residues could be simultaneously involved in the catalytic process. Movement of one pair of residues close to the substrate moves the other pair of residues away. It is therefore concluded from the kinetic effects observed for the mutants that, in the wild-type enzyme, formation of the transition state for the reaction involves a conformational change to a structure which differs from the enzyme structure in the complex with tyrosine or tyrosine adenylate. The induced fit to the transition-state structure must allow interaction with all four residues simultaneously. 

Nieto, M. and Perkins, H.R., Physicochemical properties of vancomycin and iodovancomycin and their complexes with diacetyl-L-lysyl-D-alanyl-D-alanine, Biochem. /., 123, 773, 1971. 

Sheldrick, G.M. et al.. Structure of vancomycin and its complex with acetyl-D-alanyl-D-alanine, Aafare, 271, 223, 1978. 

Trimerization of 1-alkynes to substituted cyclobutadienes occurs in reactions of RhCl(l-alaninate)Cp with HC CR (R = Ph, tol), which afford Rh -C4HR2 (C=CR) Cp (310) possibly via intermediate dialkynylrhodium(III) complexes. Reductive coupling to an /j -diyne complex, which coordinates the third molecule of alkyne, is followed by further coupling to the rhodacyclopentadiene and reductive elimination of the cyclobutadiene (Scheme 72). ... 

The measurement of stability constants of complexes of yttrium, lanthanide, and actinide ions with oxalate, citrate, edta, and 1,2-diaminocyclohexanetetra-acetate ligands has revealed that there is a slight increase in the stability of complexes of the /-electron elements, relative to the others. A series of citric acid (H cit) complexes of the lanthanides have been investigated by ion-exchange methods and the species [Ln(H2cit)]", [Ln(H2cit)2] , [Ln-(Hcit)], and [Ln(Hcit))2] were detected. Simple and mixed complexes of dl- and jeso-tartaric acid have been obtained with La " and Nd ions, and the stability constants of lactate, pyruvate, and x-alaninate complexes of Eu and Am " in water have been determined. 

From Table 8 it is obvious that the resolution always increases with an increase of the number of benzene rings and that riboflavine is a more powerful selector than the nucleotides, but not as good as TAPA. An interesting experiment shows that it is not always necessary to have the selector coated or bound to the solid phase but that it can sometimes be used as well, dissolved in the mobile phase. The n-dodecyl ester of N-(2,4-dinitrophenyl)-L-alanine is able to discriminate between the enantiomers of l-aza-[6]-helicene, when used as a chiral dopant in the mobile phase in HPLC on a reversed phase column 93) (see Table 9). The usefulness of this dopant must be due to the known ability of a dinitrophenyl moiety to form CT-complexes with polycyclic aromatic hydrocarbons the presence of a chiral site near this group causes resolution of helicenes, because the steric interactions in diastereomeric complexes will be quite different. 

Several V02+ complexes with (107) and (108) derived from dibenzoylmethane or pyrrole-2-carboxyaldehyde and several amines (taurine, anthranilic acids, /I-alanine) were formulated as [VO(SB)(H2O)2] 780 783 it was proposed that these SBs behave as tridentate ligands and assume a monomeric structure on the basis of fiia and ebulliometric measurements in dioxane. A pyridine adduct [VO(PE)(py)2] was also obtained where PE is the SB (108 R—O = CH2CH2SOj).782... 

Complexes with SBs from Hsal and ar-amino acids (glycine, l- and DL-alanine, L-methionine, L-valine, L-leucine, l- and DL-phenylalanine) were prepared and characterized.786 The complexes are bluish-grey and there is no appreciable interaction between V atoms. The compounds were [VO(SB)(H20)] (111), confirmed in an X-ray study of (111 R = Me, L-Ala derivative).787 v(V=0) was at —1000 cm-1 the compounds are not soluble in noncoordinating solvents, but when dissolved in py v(V=0) shifts to —970 cm-1 several orange py adducts (112) were isolated.686 Complexes (111) have electronic spectra that resemble those of... 

Cadmium complexes with glycine, 3,49 histidine,263 alanine,264,266 DL-norleudne,263 valine269 and numerous other amino acids267,268 have been reported. A study of the interaction of dipeptides with cadmium ions has also been described. 69... 

Rather earlier but still recent studies include those of zinc complexes with glycine,270,273 alanine,272,274 /5-alanine,272 norleudne,271 phenylalanine,272 proline, methionine, serine,274 histidine,271 asparagine,276 adrenaline,277 noradrenaline,277 terizidone,278 S-ethyl-L-cysteine,279 5,5 -methylenebis(L-cysteine),280 ornithine, lysine, 2,4-diaminobutyric add and 2,3-diaminopropionic acid.281... 

Cadmium complexes with glycine,271-273,282-284 alanine,272,284 norleudne,271 phenylalanine,272 proline,285 serine,286 histidine, 71 asparagine,276 leudne, tyrosine, norvaline, arginine, and... 

The terdentate ligand ft-(2-pyridyl)alanine forms zinc complexes with a considerable degree of enantioselectivity.524 Zinc complexes of 2-pyridyl azo compounds,525 oximes526 and sulfonamides527 have also been described. 

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