EDC Mixtures

The discussion of EDCs to this point has addressed responses to single chemicals. Mixtures of hormone disruptors have not been well studied, but 

The pesticide DDT is an estrogen mimic that affects the body by elevating hormone levels. This, however, is not its only effect. DDE, the metabolite of DDT, is a fat soluble species that persists for long periods of time in the human body that has the opposite effect of DDT. DDE depletes hormones by accelerating their breakdown and elimination. This leaves the body with a short supply of not just estrogen, but testosterone and other steroid hormones as wellJ18  

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Fig. 30. Variation of [>/] with helical fraction for high-molecular-weight PBLG in DCA-EDC mixtures (83,102). The data points at fN = 1 are for DMF. The Nw are from top to bottom...

Fig. 37. Molecular weight dependence of dipole moment (n2 112 for PBLA and PCBL in some helicogenic solvents. The line PBLA yields 4.6 D for ph and the line PCBL yields 5.4 D for nh. Data for PBLA ( ) Erenrich and Scheraga (115), (3) Saruta et al. (116) data for PCBL (O) in m-cresol, ( ) in m-cresol-EDC mixtures (117)...

Fig. 43. Frequency dependence of chemically induced dielectric constant (e )ch and dielectric loss (s%h for PBLG in a DCA-EDC mixture (73.5 vol.-% DCA) at various equilibrium helical fractions Jas indicated (123)...

Fig. 17. Dependence of the helical twisting power on the solvent composition in dioxane-EDC mixtures. Numerals indicate the temperature in °C...

Table 5.8 Selected material properties for eddy dissipation concept (EDC) mixture.

The discussion of EDCs to this point has addressed responses to single chanicals. Mixtures of hormone disrupters have not been well-studied, but the example of the mixture effects of DDT and dichlorodiphenyldichloroethylene (DDE) is an illnstra-tion of how an EDC mixture can produce unexpected effects. 

Direct Chlorination of Ethylene. Direct chlorination of ethylene is generally conducted in Hquid EDC in a bubble column reactor. Ethylene and chlorine dissolve in the Hquid phase and combine in a homogeneous catalytic reaction to form EDC. Under typical process conditions, the reaction rate is controlled by mass transfer, with absorption of ethylene as the limiting factor (77). Ferric chloride is a highly selective and efficient catalyst for this reaction, and is widely used commercially (78). Ferric chloride and sodium chloride [7647-14-5] mixtures have also been utilized for the catalyst (79), as have tetrachloroferrate compounds, eg, ammonium tetrachloroferrate [24411-12-9] NH FeCl (80). The reaction most likely proceeds through an electrophilic addition mechanism, in which the catalyst first polarizes chlorine, as shown in equation 5. The polarized chlorine molecule then acts as an electrophilic reagent to attack the double bond of ethylene, thereby faciHtating chlorine addition (eq. 6) ... 

Alternatives to oxychlorination have also been proposed as part of a balanced VCM plant. In the past, many vinyl chloride manufacturers used a balanced ethylene—acetylene process for a brief period prior to the commercialization of oxychlorination technology. Addition of HCl to acetylene was used instead of ethylene oxychlorination to consume the HCl made in EDC pyrolysis. Since the 1950s, the relative costs of ethylene and acetylene have made this route economically unattractive. Another alternative is HCl oxidation to chlorine, which can subsequently be used in dkect chlorination (131). The SheU-Deacon (132), Kel-Chlor (133), and MT-Chlor (134) processes, as well as a process recently developed at the University of Southern California (135) are among the available commercial HCl oxidation technologies. Each has had very limited industrial appHcation, perhaps because the equiHbrium reaction is incomplete and the mixture of HCl, O2, CI2, and water presents very challenging separation, purification, and handling requkements. HCl oxidation does not compare favorably with oxychlorination because it also requkes twice the dkect chlorination capacity for a balanced vinyl chloride plant. Consequently, it is doubtful that it will ever displace oxychlorination in the production of vinyl chloride by the balanced ethylene process. 

Introduction of the C-6 acyl side chain proceeded with only modest selectivity in the presence of l-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and 4-DMAP, giving a 3 2 mixture of C-6 and C-7 acylated products (Scheme 26).60 However,... 

The sheer complexity of environmental mixtnres of EDCs, possible interactive effects, and capacity of some EDCs to bioaccumulate (e.g., in fish, steroidal estrogens and alkylphenolic chemicals have been shown to be concentrated up to 40,000-fold in the bile [Larsson et al. 1999 Gibson et al. 2005]) raises questions about the adequacy of the risk assessment process and safety margins established for EDCs. There is little question that considerable further work is needed to generate a realistic pictnre of the mixture effects and exposure threats of EDCs to wildlife populations than has been derived from studies on individual EDCs. Further discussion of the toxicity of mixtures will be found in Chapter 2, Section 2.6. 

Add 150 mg (0.78 mmol) of EDC to the buffer solution. Stir the mixture at room temperature to allow aU the reagents to dissolve... 

Add EDC (Thermo Fisher) to the above solution to obtain at least a 10-fold molar excess of EDC to the protein. Alternatively, a 0.5-0.1 M EDC concentration in the reaction mixture usually works well. To make it easier to add the correct quantity of EDC, a higher concentration stock solution may be prepared if it is dissolved and used immediately. To prepare the peptide-protein conjugate, add the solution from step 3 to 10 mg of EDC in a test tube. Mix to dissolve. If this ratio of EDC to peptide or protein results in precipitation, scale back the amount of carbodiimide addition until a soluble conjugate is obtained. For some proteins, as little as 0.1 times this amount of EDC may have to be used to maintain solubility. 

Add 1.4 pi of 2-mercaptoethanol to each ml of the reaction mixture to quench excess EDC. Sonicate the QD solution several times to maintain particle dispersion. 

Figure 19.9 Conjugation of the biological peptide [Met5]-enkephalin to BSA using EDC. The graph shows the gel filtration profile (on Sephadex G-25) after completion of the conjugation reaction. A blank run with no added EDC was done to illustrate the peak absorbance that would be obtained if no conjugation took place. With addition of 10 mg of EDC to a reaction mixture consisting of 2 mg of BSA plus 2 mg of peptide, nearly complete conjugate formation was obtained.

Add 10mg EDC per ml of lipid/protein mixture. Solubilize the carbodiimide using a vortex mixer. 

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