Solubilization complexation

Cyclodextrins can also be used to decrease the solubility of compounds. Insoluble derivatives of cyclodextrins decrease the rate of release of drugs, resulting in maintaining a level of drug over a prolonged period, because two steps are involved in the release of the drug dissolution of the complex and release of the drug from the solubilized complex. 

Finally, anion activation can also be achieved by the complexation of the cation using suitable macro(poly)cyclic Hgand molecules [643]. Organic Hgands that contain enforced cavities of dimensions at least equal to those of the smaller cations (and anions) have been called cavitands [644]. Cation complexation by such macro(poly)cyclic ligands leads to dissociation of the ion pairs as well as to salt solubilization. Complex... 

Beekman, L. M. P., Visschers, R. W., Monshouwer, R., Heer-Dawson, M., Mattioli, T. A., McGlynn, P., Hunter, C. N., Robert, B., Van Stokkum, 1. H. M., Van Grondelle, R., and Jones, M. R., 1995, Time-resolved and steady-state spectroscopic analysis of membrane-bound reaction centers from Rhodobacter sphaeroides Comparisons with detergent-solubilized complexes. Biochemistry, 34 14712914721. 

Because the concentration of the metal complex moiety in the polymer domain of a solid-state film is higher than that of a homogeneously solubilized complex in solution, even a simple spectrophotometer is effective for observing the gaseous molecule-binding reactions and ligand-bonding characteristics of complexes. 

Figure 6. A metal-directed reaction leading to a solubilized complex with pendant hydroxyethyl groups.

To overcome this problem, we have recently used an alternative method, isoelectrofocussing, allowing a separation on the basis of the charge characteristics (pi) of the solubilized complexes. A typical separation is shown in figure 1. 

Large (3 - 7 pm diam.) two-dimensional crystals of pea LHC-II form by dialysis of the detergent-solubilized complex at 35 - 40 °C against monovalent cations (3), or upon heating to this temperature in the presence of KCI and glycerol. Addition of lipid is not necessary since the solubilized complex contains approximately 1.3 molecules of thylakoid lipid per molecule of chlorophyll (D.J. Chapman, personal communication). 

When detergent-solubilized complexes from chromatophores were subjected to gel-permeation chromatography, Bchl-containing (A740) complexes came off as a rathw broad peak (ftraction A). The A810 peak (fraction B), which itself was buried in the former on A740 basis, came out later (Fig.l). The absorption spectra of Actions A and B are shown in Fig.2. The q)ectrum of the fraction B has some characteristics of those of the reaction center preparation reported by Fowler et al.(7), and we concluded that it is a reaction center-rich fraction. 

If A is in excess of B then the formed complex (which is hydrophobic) may be solubilized by the micelles of the alkylsulphate. As B" remaining in solution hydrolyses, then some of this (solubilized) complex will be mobilized. This serves to maintain the B monomer concentration in solution. 

Treatment of the native, solubilized complex with small amounts of trypsin led to the disappearance of the 27 kO band on SDS gels, while the 25 kO band remained visible. 

Simplest examples are prepared by the cyclic oligomerization of ethylene oxide. They act as complexing agents which solubilize alkali metal ions in non-polar solvents, complex alkaline earth cations, transition metal cations and ammonium cations, e.g. 12—crown —4 is specific for the lithium cation. Used in phase-transfer chemistry. ... 

Surfactants have also been of interest for their ability to support reactions in normally inhospitable environments. Reactions such as hydrolysis, aminolysis, solvolysis, and, in inorganic chemistry, of aquation of complex ions, may be retarded, accelerated, or differently sensitive to catalysts relative to the behavior in ordinary solutions (see Refs. 205 and 206 for reviews). The acid-base chemistry in micellar solutions has been investigated by Drummond and co-workers [207]. A useful model has been the pseudophase model [206-209] in which reactants are either in solution or solubilized in micelles and partition between the two as though two distinct phases were involved. In inverse micelles in nonpolar media, water is concentrated in the micellar core and reactions in the micelle may be greatly accelerated [206, 210]. The confining environment of a solubilized reactant may lead to stereochemical consequences as in photodimerization reactions in micelles [211] or vesicles [212] or in the generation of radical pairs [213]. 

In the first method a secondary acetylenic bromide is warmed in THF with an equivalent amount of copper(I) cyanide. We found that a small amount of anhydrous lithium bromide is necessary to effect solubilization of the copper cyanide. Primary acetylenic bromides, RCECCH Br, under these conditions afford mainly the acetylenic nitriles, RCsCCHjCsN (see Chapter VIII). The aqueous procedure for the allenic nitriles is more attractive, in our opinion, because only a catalytic amount of copper cyanide is required the reaction of the acetylenic bromide with the KClV.CuCN complex is faster than the reaction with KCN. Excellent yields of allenic nitriles can be obtained if the potassium cyanide is added at a moderate rate during the reaction. Excess of KCN has to be avoided, as it causes resinifi-cation of the allenic nitrile. In the case of propargyl bromide 1,1-substitution may also occur, but the propargyl cyanide immediately isomerizes under the influence of the potassium cyanide. 

The typical SEA process uses a manganese catalyst with a potassium promoter (for solubilization) in a batch reactor. A manganese catalyst increases the relative rate of attack on carbonyl intermediates. Low conversions are followed by recovery and recycle of complex intermediate streams. Acid recovery and purification involve extraction with caustic and heat treatment to further decrease small amounts of impurities (particularly carbonyls). The fatty acids are recovered by freeing with sulfuric acid and, hence, sodium sulfate is a by-product. 

For deliming, ammonium salts and acids are used. The proportion of ammonium salts to acids and the type of acids employed is a matter of the tanner s choice. The acid neutralizes the lime, Ca(OH)2, thereby adjusting the pH. The ammonium salts have two functions to buffer the solution to a pH required for bating, and to form calcium ammonium complexes. The acidity and the complex formation solubilize the calcium and serve to bring the hide to the desired pH. 

The covalent character of mercury compounds and the corresponding abiUty to complex with various organic compounds explains the unusually wide solubihty characteristics. Mercury compounds are soluble in alcohols, ethyl ether, benzene, and other organic solvents. Moreover, small amounts of chemicals such as amines, ammonia (qv), and ammonium acetate can have a profound solubilizing effect (see COORDINATION COMPOUNDS). The solubihty of mercury and a wide variety of mercury salts and complexes in water and aqueous electrolyte solutions has been well outlined (5). 

Only three simple silver salts, ie, the fluoride, nitrate, and perchlorate, are soluble to the extent of at least one mole per Hter. Silver acetate, chlorate, nitrite, and sulfate are considered to be moderately soluble. AH other silver salts are, at most, spatingly soluble the sulfide is one of the most iasoluble salts known. SHver(I) also forms stable complexes with excess ammonia, cyanide, thiosulfate, and the haUdes. Complex formation often results ia the solubilization of otherwise iasoluble salts. Silver bromide and iodide are colored, although the respective ions are colorless. This is considered to be evidence of the partially covalent nature of these salts. 

Sulfur Complexes. Silver compounds other than sulfide dissolve in excess thiosulfate. Stable silver complexes are also formed with thiourea. Except for the cyanide complexes, these sulfur complexes of silver are the most stable. In photography, solutions of sodium or ammonium thiosulfate fixers are used to solubilize silver hahdes present in processed photographic emulsions. When insoluble silver thiosulfate is dissolved in excess thiosulfate, various silver complexes form. At low thiosulfate concentrations, the principal silver species is Ag2(S203) 2j high thiosulfate concentrations, species such as Ag2(S203) 3 are present. Silver sulfide dissolves in alkaline sulfide solutions to form complex ions such as Ag(S 2 Ag(HS) 4. These ions are... 

Natural Ethoxylated Fats, Oils, and Waxes. Castor oil (qv) is a triglyceride high in ticinoleic esters. Ethoxylation in the presence of an alkaline catalyst to a polyoxyethylene content of 60—70 wt % yields water-soluble surfactants (Table 20). Because alkaline catalysts also effect transestenfication, ethoxylated castor oil surfactants are complex mixtures with components resulting from transesterrfication and subsequent ethoxylation at the available hydroxyl groups. The ethoxylates are pale amber Hquids of specific gravity just above 1.0 at room temperature. They are hydrophilic emulsifiers, dispersants, lubricants, and solubilizers used as textile additives and finishing agents, as well as in paper (qv) and leather (qv) manufacture. 

Enzyme—Heat—Enzyme Process. The enzyme—heat—enzyme (EHE) process was the first industrial enzymatic Hquefaction procedure developed and utilizes a B. subtilis, also referred to as B. amjloliquefaciens, a-amylase for hydrolysis. The enzyme can be used at temperatures up to about 90°C before a significant loss in activity occurs. After an initial hydrolysis step a high temperature heat treatment step is needed to solubilize residual starch present as a fatty acid/amylose complex. The heat treatment inactivates the a-amylase, thus a second addition of enzyme is required to complete the reaction. 

Chelant Control. Chelants are the prime additives in a solubilizing boiler water treatment program. Chelants have the abihty to complex many cations (hardness and heavy metals under boiler water conditions). They accomplish this by locking metals into a soluble organic ring stmcture. The chelated cations do not deposit in the boiler. When apphed with a dispersant, chelants produce clean waterside surfaces. 

A chelant—polymer combination is an effective approach to controlling iron oxide. Adequate chelant is fed to complex hardness and soluble iron, with a slight excess to solubilize iron contamination. Polymers are then added to condition and disperse any remaining iron oxide contamination. 

Salts of neodecanoic acid have been used in the preparation of supported catalysts, such as silver neodecanoate for the preparation of ethylene oxide catalysts (119), and the nickel soap in the preparation of a hydrogenation catalyst (120). Metal neodecanoates, such as magnesium, lead, calcium, and zinc, are used to improve the adherence of plasticized poly(vinyl butyral) sheet to safety glass in car windshields (121). Platinum complexes using neodecanoic acid have been studied for antitumor activity (122). Neodecanoic acid and its esters are used in cosmetics as emoUients, emulsifiers, and solubilizers (77,123,124). Zinc or copper salts of neoacids are used as preservatives for wood (125). 

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