Macromolecular titration

Macroscopic Electrostatics Calculation of Solvated Interactions and Macromolecular Titration... 

A major reason why simulations of biological systems are so time-consuming is the large number of solvent molecules which must be included. Thus, it is important to try to develop accurate continuum models which can represent the solvent implicitly approaches are described in articles by Bashford Macroscopic Electrostatics Calculation of Solvated Interactions and Macromolecular Titration) and Sharp Continuum Solvation). 

Fig. 1. Titration of (EtO)2P(0)SMe with Me3SiI in CH2CL at -70°C followed by conductance (A---A) and 3IP-NMR spectroscopy (O—O). [(EtO)2P(0)SMe] , 0.1 mol/dnr1 (conductance) or 0.5 mol/dm3 (NMR). (From M. Cypryk, Ph.D thesis. Centre of Molecular and Macromolecular Studies, The Polish Academy of Sciences, t 6di, Poland, 1982. See also Ref. 256.)...

The experimental results may be represented both by the titration curves or property-composition dependences. The extremums or bends on the titration curves indicate the formation of complexes and their composition. Thus, investigating the-possi-bility of complex formation in polyelectrolyte - nonionic polymer systems, one can use the methods of conductometric and potentiometric titration. The formation of interpolymer complexes in these systems, as some authors suggest18,211, is caused by a co-operative formation of hydrogen bonds between carboxy groups of the polyacid and oxygen atoms of nonionic polyvinylpyrrolidone or poly(ethylene glycol) and is therefore accompanied by an increase of pH of the solution. The typical titration curves for the system polyvinylpyrrolidone - copolymer maleic anhydride and acrylic add are shown in Fig. 1. The inflection points of the titration curves indicate the ratio at which the macromolecular components react with each other, i.e. the composition of the formed complexes. 

Ligand-macromolecular macromolecules (e.g., multimeric or membrane-bound receptors) Stoichiometry of complex Chemical shift/titration... 

More commonly, titrations involving iodine are performed with a suspension of starch as an indicator. The deep blue color that develops in the presence of iodine is believed to arise from the absorption of iodine into the helical chain of j8-amylose (see Figure 20-2), a macromolecular component of most starches. The closely related a-amylose forms a red adduct with iodine. This reaction is not easily reversible and is thus undesirable. In commercially available soluble starch, the alpha fraction has been removed to leave principally j8-amylose indicator solutions are easily prepared from this product. 

Synthesis was carried out of the copolymers of 4-vinylpyridine (4VP), styrene (St) and divinylbenzene (DVB) with varied compositions, P(4VP-St-DVB), by suspensionpolymerisationusing 2,2 -azobisisobutyronitrile (AIBN) as an initiator. Preparation of the insoluble (crosslinked) pyridinium-type polymers in benzyl-pyridinium bromide form, which possess various macromolecular chain compositions, was performed by the reaction of eachP(4VP-St-DVB) with benzyl bromide (BzBr), respectively. By using different halohydrocarbon RX in the quatemisation of P(4VP-St-DVB), the insoluble pyridinium-type polymers with various pyridinium group stractures were obtained. FTIR was nsed to identify the stractures of P(4VP-St-DVB) and its quatemised product Q-P(4VP-St-DVB). The 4VP content in each copolymer P(4VP-St-DVB) was measured by non-aqueous titration and the pyridinium group content (Cq) in each Q-P(4 VP-St-DVB) sample was determined by means of the back titration manner in argentometiy and/or the elemental analysis method, respectively. Also, the particle structure... 

Heux et al. (2000) found that after partial deacetylation (<50%), the product of chitin becomes soluble in acidified water. Therefore, chitosan is characterized by its DA, which is the average mole fraction/percentage of A-acetyl-D-glucosaminc units within the macromolecular chain (Desbrieres, 2002). Alternatively, Heux et al. (2000) calculated DA by measuring all carbonyl or methyl groups divided by the integral of all the carbon atoms in the backbones. The DD may be determined by a titration method in which chitosan is dissolved in 0.1% acetic acid to form a 0.01% solution. This is followed by titration with 0.0025 N poly (vinyl sulfate) potassium salt (PVSK) with 1% toluidine blue (TBO) as an indicator. The acetyl content of... 

The characteristic of this procedure is that two of the arms are incorporated by titration. The difficulty for the introduction of the arms gradually increases and consequently the more sterically hindered polyanions have to react first. For this reason, P4MeSLi was chosen to react with the trifunctional macromolecular linking agent and the less sterically hindered PILi with the difunctional linking agent. It is obvious that the sequence of addition of the arms is crucial for this procedure. 

NB Cited in Larsen C, Macromolecular prodrugs. XIII. Determination of the ionization constant of dextran by potentiometric titration and from kinetic analysis of the hydrolysis of dextran indomethacin ester conjugates, Int.. Pharm., 52, 55-61 (1989). 

From an electrometric titration with acid or alkali one can determine the charge of a macromolecular electrolyte as a function of the pH. It is true one encounters... 

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