Iodoacetic acid

Methylene iodide [75-11-6], CH2I2, also known as diio dome thane, mol wt 267.87, 94.76% I, mp 6.0°C, and bp 181°C, is a very heavy colorless Hquid. It has a density of 3.325 g/mL at 20°C and a refractive index of 1.7538 at 4°C. It darkens in contact with air, moisture, and light. Its solubiHty in water is 1.42 g/100 g H2O at 20°C it is soluble in alcohol, chloroform, ben2ene, and ether. Methylene iodide is prepared by reaction of sodium arsenite and iodoform with sodium hydroxide reaction of iodine, sodium ethoxide, and hydroiodic acid on iodoform the oxidation of iodoacetic acid with potassium persulfate and by reaction of potassium iodide and methylene chloride (124,125). Diiodoform is used for determining the density and refractive index of minerals. It is also used as a starting material in the manufacture of x-ray contrast media and other synthetic pharmaceuticals (qv). 

For deterrnination of tryptophan, 4 M methanesulfonic acid hydrolysis is employed (18). For cystine, the protein is reduced with 2-mercaptoethanol, the resultant cysteine residue is carboxymethylated with iodoacetic acid, and then the protein sample is hydroly2ed. Also, a one-pot method with mercaptoethanesulfonic acid has been developed for tryptophan and cystine (19). 

How might iodoacetic acid affect the glyceraldehyde-3-phosphate dehydrogenase reaction in glycolysis Justify your answer. 

Problem 26.10 1 Show the structure of the product you would expect to obtain by SN2 reaction of a cysteine residue with iodoacetic acid. 

Aqueous solutions of aequorin also emit light upon the addition of various thiol-modification reagents, such as p-quinone, Br2, I2, N-bromosuccinimide, N-ethylmaleimide, iodoacetic acid, and p-hydroxymercuribenzoate (Shimomura et al., 1974b). The luminescence is weak and long-lasting ( 1 hour). The quantum yield varies with the conditions, but seldom exceeds 0.02 at 23-25°C. The luminescence is presumably due to destabilization of the functional moiety caused by the modification of thiol and other groups on the aequorin molecule. 

The action of a peptidase can be neutralized by an inhibitor. Some inhibitors are very broad in their action and are capable of inhibiting many different peptidases, including peptidases of different catalytic types. Some inhibitors are assumed to be specific for a particular catalytic type, but can inhibit peptidases of different types. Leupeptin, for example, is widely used as an inhibitor of serine peptidases from family SI, but it is also known to inhibit cysteine peptidases from family Cl. Cysteine pqrtidase inhibitors such as iodoacetic acid interact with the thiol of the catalytic cysteine. However, this reduction can occur on any thiol group and can affect other, predominantly intracellular, peptidases with a thiol dependency. One example is thimet oligopepti-dase. Metal chelators such as EDTA can inhibit meta-llopeptidases, but can also affect peptidases that have a requirement for metal ions that is indq>endent of their catalytic activity, such as the calcium-dependent cysteine endopqrtidase calpain 1. 

Ribosomal protein L12 was oxidized with 0.3 M H202 at 30°C for 1 h. After dialysis, the protein was incubated in the presence of 0.8 M 2-mercaptoethanol for 48 min at 37 °C and dialyzed. The amount of methionine residues was quantitated by exhaustive alkylation of the protein with [14C]iodoacetic acid. 

Cemeli E, ED Wagner, D Anderson, SD Richardson, MI Plewa (2006) Modulation of the cytoxicity and geno-toxicity of the drinking water disinfection byproduct iodoacetic acid by suppressors of oxidative stress. Environ Sci Technol 40 1878-1883. 

Asymmetric additions of Reformatsky-type reagents to nitrones 258a and 258b have also been reported (Scheme 139). The reagents were prepared in situ from ZnEt2 and the corresponding iodoacetic acid ester. Diisopropyl (R,R)-tartrate 262 was employed as a chiral inductor. Enantioselectivities varied significantly the best results were obtained at 0 °C when a nitrone was added to the reaction mixture over a 2 h period. 

Add iodoacetate to a concentration of 50mM in the reaction solution. Alternatively, add a quantity of iodoacetate representing a 10-fold molar excess relative to the number of —SH groups present. An estimation of the sulfhydryl content in the protein to be modified can be accomplished by performing an Ellman s assay (Chapter 1, Section 4.1). Readjust the pH if necessary. To aid in adding a small quantity of iodoacetic acid to the reaction, a concentrated stock solution may be made in the reaction buffer, the pH re-adjusted, and an aliquot added to the protein solution to give the desired concentration. 

Figure 22.30 An iodoacetamide derivative of PE containing an extended spacer arm can be constructed through a carbodiimide coupling of iodoacetic acid to PE, followed by reaction with 2-mercaptoethylamine, and finally another reaction with iodoacetate.

Figure 25.18 An amine-derivative of dextran may be coupled with iodoacetic acid using a carbodiimide reaction to produce a sulfhydryl-reactive iodoacetamide polymer.

Rees, J.F. and F. Baguet. 1989. Metabolic control of luminescence in the luminous organs of the teleost Porichthys effects of the metabolic inhibitors iodoacetic acid and potassium cyanide. Jour. Exper. Biol. 143 347-357. 

Iodism, 14 368 Iodized salt, 22 815-816 Iodoacetate, antiaging agent, 2 813 Iodoacetic acid, 1 143 Iodoacetyl/bromoacetyl methods, for... 

Identification of the energy source for muscle contraction and determination of the order in which the phosphate esters were metabolized was helped by the use of inhibitors. These inhibitors blocked different stages in glycolysis and caused preceding substrates to accumulate in quantities which could greatly exceed those normally present. The compounds were then isolated, identified, and used as specific substrates to identify the enzymes involved in their metabolism. Iodoacetic acid (IAc) was one of the most important inhibitors used to analyze glycolysis. 

FIGURE 4 Effect of sample preparation on the fragmentation of an rMAb observed in (A) SDS-PAGE and (B) CE-SDS with LIF detection. SDS-PAGE lanes (Lane I) molecular weight standards bovine serum albumin at (Lane 2) 8 ng and (Lane 3) 2 ng (Lane 4) rMAb control after alkylation with (Lane 5) iodoacetic acid and (Lane 6) iodoacetamide. (See color plate 4.)... 

Fig. 3.4 Relationship between the stability constant, Pioi, for formation of SmL and the acid constant, of HL (1) propionic acid (2) acetic acid (3) iodoacetic acid (4) chloroacetic acid (5) benzoic acid (6) 4-fluorobenzoic acid (7) 3-fluorobenzoic acid and (8) 3-nitrobenzoic acid. 

Recently, Duirk et al. [34] showed evidence that iodinated X-ray contrast media (ICM), such as iopamidol, constitute an iodine source to form iodo-THM DBFs, e.g., dichloroiodomethane, and iodo-acid DBFs, e.g., iodoacetic acid, in chlorinated and chloraminated drinking waters. However, the complete reaction pathway is not fully understood yet, and it is under further investigation. Chloraminated and chlorinated source waters with iopamidol were genotoxic and cytotoxic in mammalian cells. This is in agreement with the previously reported high genotoxicity and cytotoxicity of the iodo-acids and iodo-THMs [20, 21]. 

MS, chemical ionization-MS, and sometimes GC/infrared spectroscopy (IR) have been used with GC/MS to obtain structural information. Examples of the use of GC/ MS for identifying new DBFs include the recent identification of iodo-acids. The iodo-acids were discovered in drinking water treated with chloramination through the use of full-scan GC/MS on the methylated extracts. Empirical formula information for both the molecular ions and the fragment ions was obtained by high-resolution electron ionization (EI)-MS, and the spectra were interpreted to yield tentative identifications of five new iodo-acids (iodoacetic acid, bromoiodoacetic acid, ( )-3-bromo-3-iodopropenoic acid, (Z)-3-bromo-3-iodopropenoic acid, and )-2-iodo-3-methylbutenedioic acid). Structural assignments were then confirmed by the match of mass spectra and GC retention times to authentic chemical standards, several of which had to be synthesized. 

Shi and Adams recently created a rapid IC/ICF-MS method for simultaneously measuring iodoacetic acids, bromoacetic acids, iodate, and bromate in drinking water, groundwater, surface water, and swimming pool water [165]. Method detection limits were sub-pg/L for iodinated DBFs, and low-pg/L for brominated DBFs. 

Shi HL, Adams C (2009) Rapid IC-ICP/MS method for simultaneous analysis of iodoacetic acids, bromoacetic acids, bromate, and other related halogenated compounds in water. Talanta 79 523-527... 

In another experiment (J ) we treated ozone-resistant and ozone-susceptible varieties of tobacco with toxic doses of oc-iodoacetic acid, and a-iodoacetamide, both sulfhydryl-binding reagents. The symptoms produced by both compounds were similar to those produced by ozone. The severity of the injury also paralleled ozone resistance (Table II). The degree of injury caused by these two compounds also paralleled the ozone susceptibility of leaves of different ages on the same plant. The uppermost, youngest, leaves appear to be most resistant to both the sulfhydryl-binding reagents and to ozone. 

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