Ethylenediaminetetraacetate EDTA

A chelating ligand contains two or more donor atoms in a structure that allows the ligand to wrap around the metal. Examples featured in Chapter 18 are the bidentate ligand ethylenediamine (en, chemical formula H2 NCH2 CH2 NH2) and the hexadentate ethylenediaminetetraacetate (EDTA). 

The heavy metals copper, manganese, cobalt and zinc were omitted individually and in combination from MS and B5 media to determine the effect on antibody stability in solution [63]. When IgG, antibody was added to these modified media in experiments similar to the one represented in Figure 2.2, only the B5 medium without Mn showed a significant improvement in antibody retention relative to normal culture media. Nevertheless, protein losses were considerable as only about 30% of the added antibody could be detected in the Mn-free medium after about 5 h. The beneficial effect of removing Mn was lost when all four heavy metals, Cu, Mn, Co and Zn, were omitted simultaneously. The reason for these results is unclear. Addition of the metal chelating agent ethylenediaminetetraacetate (EDTA) had a negligible effect on antibody retention in both MS and B5 media [63]. 

For the same purpose, Kelly and Bryske used paper impregnated with 0.1N disodium ethylenediaminetetraacetate (EDTA) and two mobile solvents the organic phase from a mixture of n-butanol, ammonia, water (4 1 5) and the organic phase from a mixture of n-butanol, acetic acid, water (4 1 5). Disodium EDTA (0.1N) works as well as Mcllvaine s buffer when it is used to treat the paper in the method of Walton et al. (49). A circular paper chromatographic method also using paper dampened with Mcllvaine s buffer (pH 4.5) was reported by Urx et al. (50). They used a mixture of chloroform and n-butanol (4 1) as the mobile solvent. 

Ethylene cyanohydrin, 1 358, 404 10 639 Ethylenediamine, 2 129 8 485 as chelant, 5 709 molecular formula, 5 712t physical properties, 8 486t pK values, 8 487t prices of commercial, 8 496t sodium solubility in, 22 764 typical specifications, 8 496t Ethylenediaminetetraacetate (EDTA), 7 576... 

What is the titer (expressed in milligrams per milliliter) of a solution of disodium dihydrogen ethylenediaminetetraacetate (EDTA) with respect to calcium carbonate if 17.29 mL of it was needed to titrate 0.0384 g of calcium carbonate ... 

A very important ligand (or chelating agent) for titrimetric analysis is the ethylenediaminetetraacetate (EDTA) ligand. It is especially useful in reacting with calcium and magnesium ions in hard water such that water hardness can be determined. The next section is devoted to this subject. 

Specifically, disodium ethylenediaminetetraacetate (EDTA) reacts with polyvalent metal ions to result in the formation of a fairly stable water-soluble complex, or a chelate compound. 

One critical exception is the sapphyrin-ethylenediaminetetraacetic (EDTA) conjugate (23). Previous studies of small molecule-EDTA conjugates have shown that these species, in the presence of iron(II), Oj, and a suitable reducing agent, can effect the cleavage of the DNA backbone. In turn, so-called affinity cleavage can be used to elucidate the specificity of the small molecule-DNA interactions. It was thus considered worth making 23. ... 

Salt and chelate formation with edetate (ethylenediaminetetraacetate, EDTA). A In a solution of calcium disodium salt of EDTA, the sodium and hydrogen ions are chemically and biologically available. B In solutions of calcium disodium edetate, calcium is bound by coordinate-covalent bonds with nitrogens as well as by the usual ionic bonds. C In the lead-edetate chelate, lead is incorporated into five heterocyclic rings. 

The lanthanide ions are so large that they show coordination numbers of 10, 11 and even 12. Hoard and his students have shown that when ethylenediaminetetraacetate (edta) combines with the larger lanthanide ions, the sexidentate edta covers only a portion of the metal ion, the remainder being coordinated with water molecules.18... 

The T relaxation agent increased the sensitivity of the NMR instrument by decreasing several of the mono- and diester phosphate relaxation times by factors of 2-5. In this way the delay time between scans was decreased (43). This change permits an increase in the number of scans observed per unit time. Although the presence of ferric ions creates the potential for precipitation of phosphorus-iron complexes, the addition of a large molar excess of ethylenediaminetetraacetate (EDTA) relative to ferric ions prevented precipitation, even over a large pH region (44). 

As Mamiya and Gorin (11) note, Sumner occasionally had difficulty in preparing crystalline urease from some jack bean meals and this is a technical problem that has received attention in each recent improved method of preparation (11-13). Modification of Sumner s extraction procedure by including / -mercaptoethanol (11, 14) to diminish aggregation and ethylenediaminetetraacetate (EDTA) (13,15) to maintain a low concentration of metal ions has been helpful. The procedure used in this laboratory with consistent success over a period of 4 years, and involving several students, is essentially that of Mamiya and Gorin (11) but with EDTA included in the buffers. [There is an error in Mamiya and Gorin (11). The concentration of acetone used was 32%, not 36%.]... 

The effects of inhibitors and activators on RNases Ti, N1 Ui, U2, and T2 are summarized in Table IV (5, 7, 8), showing the characteristics of each RNase. Ribonuclease Ti is strongly inhibited by 10 3M Zn2+ RNases and T2 are inhibited about half but RNases N and U2 are not inhibited. Ribonuclease T, is also strongly inhibited by 10 3M Ag+, while all other RNases are inhibited about half. But 10 3 M Cu2+ strongly inhibits RNase T2 and only about half inhibits the other RNases. All five RNases are not inhibited by 10 2 M ethylenediaminetetraacetate (EDTA) and 10-3 M ICH2COOH. No metallic cofactor is required for their action. 

The thermal inactivation curve of the enzyme in 0.15 M acetate buffer-0.01 M ethylenediaminetetraacetate (EDTA), pH 5.0, showed that a 50% inactivation was obtained by heating for 20 min at 56° 11). 

Although in no case has the enzyme been purified to homogeneity, much evidence exists that the ribonudeoside 2, 3 -cyclic phosphate diesterase activity and the 3 -nucleotidase activity reside in the same protein. Thus, in all cases the ratio of the two activities remained constant throughout purification which has varied from 130-fold for the P. mirabilis enzyme (4) to 2000-fold for the enzyme from V. alginolyticus (6). Anraku (S) found that both activities from E. coli B had the same optimal pH, both showed the same behavior to activators such as Co2+, and to inhibitors [Zn2+, Cu2+, ethylenediaminetetraacetate (EDTA)], both were activated simultaneously by heating at 55° for 5 min and... 

With acyl carrier protein, ethylenediaminetetraacetate (EDTA) did not affect the activation reaction, although 02 was still required, suggesting that in this case a specific protein-protein interaction suffices to orient the SH groups in a position favorable for their oxidation. 

Fig. 8.5. Examples of complex formation by chelating ligands, showing (a) a four-membered ring with diethyldithiocarbamate (dtc), (b) formation of five-membered rings with ethylenediaminetetraacetate EDTA and (c) a six-membered ring with acetylacetonate (acac).

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