Glycine stability constants

Our direct experimental determinations of this constant were conducted at 25°C and 1.0 0.02 M Ionic strength by methods nearly Identical to those used In our oxalate and glycine stability constant determinations. The solutions used In our 8 ... 

That tetracycline and its derivatives such as chlorotetracycline and ox5Ttetracycline were chelating agents was found by determination of their stability constants (Albert and Rees, 1956), which showed that their avidity for divalent metals was similar to that of glycine. Stability constants of tetracycline are given in Table 11.2. 

Stability constants (ethylendiamine, glycinate, oxalate), surface complex formation constants and solubility products (sulfides) of transition ions. The surface complex formation constant is for the binding of metal ions to hydrous ferric oxide =Fe-OH + Me2+ =FeOMe++ H+ K. ... 

The equilibrium formation constants for the 1 1 complexes of Hf with glycine and serine in solutions of pH 2 have been determined as 31 and 18, respectively, and the HfO -amygdalic acid complex, [HfO PhCH(0)- 02)2] , has been obtained in aqueous solutions of pH 7—10.5. The stability constants of the 1 1 complexes of ZrO with iVh/ -ethylenediamine-bis(succinic acid) and Nh/ -ethylenediaminebis(glutaric acid) have been determined. ... 

The effect of the solvent properties on the polarographic behavior of Cd(II) complexes with glycine. At-acetyl, and N-benzoylglycine was studied in DM SO, acetonitrile (AN), and DMF solutions [90]. The stability constants were found to depend linearly on the acceptor numbers of the solvents. 

The cadmium complexes were also investigated potentiometrically. Using this method, the complexes of cadmium with asparagine [128], taurine [129], A -(6-ami-no-3-methyl-5-nitroso-4-oxo-3,4-dihydro-pyrimidin-2-yl)glycine [130], succinate and malate [131], acetate at different temperatures [132], pyridine oxime ligands [133], 2-hydroxypropene-l,3-diamine-Af,Af,Af, A -tetraacetic acid [134] were studied. The stoichiometry and stability constants of these complexes were determined. 

N 036 Helix-Coil Stability Constants for the Naturally Occurring Amino Acids in Water. III. Glycine Parameters from Random Poly(hydroxybutylglutamine-co-glycine)"... 

Stability constant determinations are few 1170 they are summarized in Table 100. Complexa-tion by acidic amino acids is obviously of relevance to the tanning of leather the stability constants for L-glutamic and aspartic acid1171 complexes are much greater than those for glycine or L-alanine.1172,1173,1174 This is probably because the acidic amino acids form tridentate complexes. In contrast, cysteine1173 appears to form glycine-like complexes in moderately acidic solution however, in the solid state L-cysteine is known to be tridentate vide infra). 

The most persistent and stable amino acids appear to be glycine, aspartic acid, and glutamic acid, which were reported in Paleozoic anthracite from Great Britain by Heijhenskjold and Mollerberg (8). Among the most stable amino acid chelates are those formed with copper however, the stability constants for the a-amino acids of copper do not differ to the point where they indicate that the above mentioned three acids would be preferentially preserved. 

Mixed ligand complexes of Zn2+ with en and monoethanolamine (mea) in H20-MeOH systems have been investigated.192 At <20% MeOH, the presence of the complexes [Zn(en) —(mea)3 ]2+ (n = 0-3) and the complexes [Zn(en)2]2+ and [Zn(mea)2]2+ is indicated. At >20% MeOH, only the tris complexes (n = 0 or 3) are found. Stability constants for mixed complexes of Zn2+ with en and glycine in mixed aqueous solutions of methanol, dioxane, acetonitrile and DMF have been determined.193 In general, the stability constants increase with increasing composition of the co-solvent in the order H20 < MeOH < MeCN < DMF < dioxane. 

Not mentioned in Table 2 (and often not in the original papers ) is the optical form (chirality) of the amino acids used. All the amino acids, except for glycine (R = H), contain an asymmetric carbon atom (the C atom). In the majority of cases the optical form used, whether l, d or racemic dl, makes little difference to the stability constants, but there are some notable exceptions (vide infra). Examination of the data in Table 2 reveals (i) that the order of stability constants for the divalent transition metal ions follows the Irving-Williams series (ii) that for the divalent transition metal ions, with excess amino acid present at neutral pH, the predominant spedes is the neutral chelated M(aa)2 complex (iii) that the species formed reflect the stereochemical preferences of the metal ions, e.g. for Cu 1 a 2 1 complex readily forms but not a 3 1 ligand metal complex (see Volume 5, Chapter 53). Confirmation of the species proposed from analysis of potentiometric data and information on the mode of bonding in solution has involved the use of an impressive array of spectroscopic techniques, e.g. UV/visible, IR, ESR, NMR, CD and MCD (magnetic circular dichroism). 

In order to clarify the nature of the conditional constants, we consider the reaction between Fe(III) and glycine. This complexation reaction can be characterized by the stability constant... 

The numerous Cd-PC2 species that exist in aqueous solution require specialized software for complete stability constant analysis. The basic principles behind the calculation, however, are well pointed out by considering a very simple reaction between the already doubly deprotonated amino acid, A-, and Cd2+ aqueous ion, equations (7.10)-(7.11). [Note this holds strictly only for glycine. In the cysteine system, the N-terminus is protonated (Cys should really be represented as HA).]... 

There is a linear correlation between the stability constants for the 1 1 zirconium complexes with the amino-acids glycine, alanine, P-alanine, lysine, asparagine, m-aminobenzoic acid, y-aminobutyric acid, and the pK values of the acids. Spectroscopic evidence for binding to zirconium through both the amino- and carboxy-groups has been obtained. A method for the preparation of the l-alanine complexes M(0H)2(ala)2X2,3H20 (M = Zr or Hf X = halide or NOJ) has been patented. ... 

The complexation of the Group IIB metals by amino-acid and related derivatives continues to be a subject of interest stability constants reported include those for histidine and its derivatives, histamine, glycylhistamine, aspartic and glutamic acids, aspargine, glutamine, glycine, cysteine, and alanine. " ... 

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