Carboxylate capacities

Dissociation Experiments. Solid polyelectrolyte material was dissolved in a minimum volume of 0.1 M NaOH and diluted in distilled, deionized water these solutions were stored in darkness at 4 C until ready to use. All PAA and HA concentrations used in this work are based on the milliequivalents of carboxylate binding groups per gram of poly ion in Table I. All dissociation studies employed metal concentrations that corresponded to 5% of the PAA or HA carboxylate capacity. Consequently, the following experimental matrix was used unless noted otherwise [polyelectrolyte] = 1 x 10 eq/L, [metal] = 5 x 10 M, [buffer] = 0.01 M, I = 0.1 M (NaC104). All experiments were conducted at room temperature. 

Determination of carboxyl capacity For the determination of carboxyl content 100 mg of the resin was equilibrated with HCl (0.2 mol L, 10 mL) for 24 h with magnetic stirring. The resin samples were filtered, washed with distilled water to remove unreacted HCl and the filtrate was titrated with NaOH (0.2 mol L ) to a phenolphthalein end point. The polymer contains -3.3 mmol g carboxylic acid groups. 

Hence, despite much information concerning the CAM rhythmic phenomena, an unequivocal model is lacking. We do not know, for example, if the CO2 rhythm is the result of changing CO2 production capacity or a rhythmic alteration in carboxylation capacity. Until now, only a dark CO2 fixation rhythm is established. 

Hydroxy acids compounds that contain both a hydroxyl and a carboxylic acid function have the capacity to form cyclic esters called lactones This intramolecular esterification takes place spontaneously when the ring that is formed is five or six membered Lac tones that contain a five membered cyclic ester are referred to as 7 lactones, their six membered analogs are known as 8 lactones... 

Carboxylate exchangers contain —COOH groups which have weak acidic properties and will only function as cation exchangers when the pH is sufficiently high (pH > 6) to permit complete dissociation of the —COOH site. Outside this range the ion exchanger can be used only at the cost of reduced capacity. 

Some of the physical properties of fatty acid nitriles are Hsted in Table 14 (see also Carboxylic acids). Eatty acid nitriles are produced as intermediates for a large variety of amines and amides. Estimated U.S. production capacity (1980) was >140, 000 t/yr. Eatty acid nitriles are produced from the corresponding acids by a catalytic reaction with ammonia in the Hquid phase. They have Httie use other than as intermediates but could have some utility as surfactants (qv), mst inhibitors, and plastici2ers (qv). 

Synthetic phenol capacity in the United States was reported to be ca 1.6 x 10 t/yr in 1989 (206), almost completely based on the cumene process (see Cumene Phenol). Some synthetic phenol [108-95-2] is made from toluene by a process developed by The Dow Chemical Company (2,299—301). Toluene [108-88-3] is oxidized to benzoic acid in a conventional LPO process. Liquid-phase oxidative decarboxylation with a copper-containing catalyst gives phenol in high yield (2,299—304). The phenoHc hydroxyl group is located ortho to the position previously occupied by the carboxyl group of benzoic acid (2,299,301,305). This provides a means to produce meta-substituted phenols otherwise difficult to make (2,306). VPOs for the oxidative decarboxylation of benzoic acid have also been reported (2,307—309). Although the mechanism appears to be similar to the LPO scheme (309), the VPO reaction is reported not to work for toluic acids (310). 

The smooth conversion of the enol acetate (151) into an A -acyl derivative (152) under extremely mild conditions points to the high acylating capacity of these esters. This cleavage of isoxazolium salts is also caused by other anions of carboxylic acids, and thus they can be readily converted to reactive enol esters. A very convenient and specific synthesis of peptides due to Woodward et is based on... 

Yosida et al. [41] found that p-t< rr-butylcalix[6]ar-ene can extract Cu from the alkaline-ammonia solution to the organic solvent. Nagasaki and Shinkai [42] described the synthesis of carboxyl, derivatives of calix-[n]arenes ( = 4 and 6) and their selective extraction capacity of transition metal cations from aqueous phase to the organic phase. Gutsche and Nam [43] have synthesized various substituted calix[n]arenes and examined the complexes of the p-bromo benzene sulfonate of p-(2-aminoethyl)calix[4]arene with Ni, Cu , Co-, and Fe. ... 

The steady structure determined by the value of Kw (Fig. 1) for the entire class of carboxylic CP obtained by precipitation copolymerization is one of the most important factors determining the possibility of reversible bonding of proteins absorbed by carboxylic CP with a high sorption capacity [16,19]. Thus, for the MA-HHTT system (Fig. 2), a complete desorption of enzyme is carried out on crosslinked copolymers characterized by low Kw values. In crosslinked structures exhibiting looser structure (Kw P 1), owing to the mobility of chain fragments of CP especially in the process of desorption, the macromolecules of sorbed protein are irreversibly captured as a result of a marked polyfunctional interaction. 

Fig. 13. Relative sorption capacity of proteins by carboxylic CP Biocarb-T vs pH of solution 1) terrilytin, 2) insulin, 3) chymotrypsinogen, 4) pancreatic ribonuclease, 3) pepsin, 6) thymarine, 7) thermolysine, 8) haemoglobin, P) lysozyme. mma, — quantity of protein bonden on Biocarb-T by pHma (...

High sorption capacities with respect to protein macromolecules are observed when highly permeable macro- and heteroreticular polyelectrolytes (biosorbents) are used. In buffer solutions a typical picture of interaction between ions with opposite charges fixed on CP and counterions in solution is observed. As shown in Fig. 13, in the acid range proteins are not bonded by carboxylic CP because the ionization of their ionogenic groups is suppressed. The amount of bound protein decreases at high pH values of the solution because dipolar ions proteins are transformed into polyanions and electrostatic repulsion is operative. The sorption maximum is either near the isoelectric point of the protein or depends on the ratio of the pi of the protein to the pKa=0 5 of the carboxylic polyelectrolyte [63]. It should be noted that this picture may be profoundly affected by the mechanism of interaction between CP and dipolar ions similar to that describedby Eq. (3.7). 

Alpert has shown [47] that poly(succinimide)-silica can be further hydrolyzed to poly (aspartic acid)-silica or condensed with [3-alanine in aqueous solution to form a covalently bonded copolymer of 2-carboxyethyl aspartamide and aspartic acid. The content of carboxyl groups generated by this way has not been quantified directly, but the cation-exchange hemoglobin capacity has been measured for a series of the packings. Thus, the optimal concentration of poly(succinimide) used in the synthesis was found to be 2 5%. 

In bone, three proteins have been described which are vitamin K-dependent, osteocalcin (bone Gla protein), matrix Gla protein (MGP), and protein S. Osteocalcin is synthetized by osteoclasts, regulated by the active form of vitamin D, calcitriol. Its capacity to bind calcium needs a vitamin K-dependent y-carboxylation of three glutamic acid residues. The calcium binding capacity of osteocalcin indicates a possible role in bone mineralization, but its exact function is still unclear. However, it is widely used as a serum marker for bone mineralization. Protein S, mainly a coagulant, is also vitamin-K dependent and synthesized in the liver. Children with... 

About half of the dissolved organic carbon may appear in humic or fulvic acids. These are high-molecular weight organic compounds of a composition which is somewhat uncertain. They contain aromatic hydroxyl and carboxyl groups which have the ability to bind to metal ions. Rivers and estuaries typically contain 10 mg/liter of acid with an exchange capacity of 5-10 mmol/g, mainly due to carboxylic... 

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