Chelating agents, citrate/EDTA

The isolation of bacterial DNA described in this experiment, patterned after the work of Marmur (1961), accomplishes these objectives. Bacterial cells are disrupted by initial treatment with the enzyme, egg-white lysozyme, which hydrolyzes the peptidoglycan that makes up the structural skeleton of the bacterial cell wall. The resultant cell walls are unable to withstand osmotic shock. Thus, the bacteria lyse in the hypotonic environment. The detergent, sodium dodecyl sulfate, (SDS, sodium do-decyl sulfate) then completes lysis by disrupting residual bacterial membranes. SDS also reduces harmful enzymatic activities (nucleases) by its ability to denature proteins. The chelating agents, citrate and EDTA (ethylenediamine tetraacetic acid), also inhibit nucleases by removing divalent cations required for nuclease activity. 

Treatment with chelating agents such as EDTA which removes divalent ions, leads to dissociation of cell monolayers and release of the cells into suspension without protease action. Perfusion of rat liver with citrate solutions has also been used in attempts to produce primary liver cell cultures. 

Results of an in vitro experiment in this study indicated that the midsection had greater uptake than the duodenum or ileum and that oxalate significantly (p<0.05) increased, while phytate significantly (p<0.05) decreased the transport of chromium(III) across all three sections, paralleling the in vivo results. Ethylenediamine tetraacetic acid (EDTA) and citrate were also tested in the in vitro system, but were found to have no effect on chromium(III) intestinal transport therefore, these chelating agents were not tested in vivo (Chen et al. 1973). 

Avoidance of interference of other milk constituents with measurements is also of importance for example, dissociation of casein micelles by calcium-chelating agents, such as trisodium citrate or ethylenediamine tetra-acetic acid (EDTA), may used to avoid interference of the micelles in particle size measurement, while clusters of fat globules can be disrupted by adding a low level of sodium dodecyl sulphate (SDS). 

Acceptor alcohols (methanol, glycerol, 2-ME, Tris) stimulate the cleavage of o-NPG, but not of other substrates. Heavy metals, orga-no-mercuric compounds, chelating agents (EDTA, citrate), prevent... 

Clearly, there exist only few enhancers of zinc absorption. Gluconate, citrate and chelating agents (e.g., EDTA) have been shown to enhance absorption in animal experiments (Oberleas et al. 1966, Suso and Edwards 1968, 1972, Maher 1999). Histidine, cysteine, glycine and aspartate have also been shown to increase intestinal zinc absorption in animal experiments, and this may explain the better availability of zinc... 

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