Curve-fitting, mixture experiments

Fig. 3.16 The ALIS-MS responses from a dissociation rate experiment for a mixture of Zap-70 ligands using staurosporine as the quench reagent. See text for details. (A) The raw data and its fit curve for NGD-6367, one of the compounds in the mixture. (B) The exponential decay curves fit to normalized...

Pyrazolyl and substituted pyrazolyl porphyrins have been shown to form linear dimers 18 and cycHc tetramers 19 in CDCI3 solution [29]. The aggregation is destroyed in protic solvents such as methanol, and dilution experiments were utilized to estimate the possible structure of the association. The data were fitted to a mixture of dimer and tetramer, and the presence of other cycUc -mers was discounted on the basis of the curve fitting. The dimerization constant, K2 = 39 M obtained from the curve fitting of 18, was lower than the tetramerization constant K4 = 9.3 x 10 of 19. 

Laity and Treybal (LI) report on experiments with a variety of two-phase systems in a covered vessel which was always run full, so that there was no air-liquid interface at the surface of the agitated material. Under these circumstances no vortex was present, even in the case of operation without baffles. Mixing Equipment Company flat-blade disk-turbines were used in 12- and 18-in. diameter vessels whose heights were about 1.07 times their diameters. Impeller diameter was one-third of tank diameter in each case. For operation without baffles, using only one liquid phase, the usual form of power-number Reynolds-number correlation fit the data, giving a correlation curve similar to that given in Fig. 6 for disk-turbines in unbaffled vessels. In this case, however, the Froude number did not have to be used in the correlation because of the absence of a vortex. For two-phase mixtures, Laity and Treybal could correlate the power consumption results for unbaffled operation by means of the same power number-Reynolds number correlation as for one-phase systems provided the following equations were used to calculate the effective mean viscosity of the mixture For water more than 40% by volume ... 

The consecutive reduction of two substances O and O in a potential scan experiment is more complicated than in the potential step (or sampled-current voltammetric) experiment treated in Section 5.6 (15, 16). As before, we consider that the reactions O ne and O + n e R occur. If the diffusion of O and O takes place independently, the fluxes are additive and the i-E curve for the mixture is the sum of the individual i-E curves of O and O (Figure 6.6.1). Note, however, that the measurement of /p must be made using the decaying current of the first wave as the baseline. Usually this baseline is obtained by assuming that the current past the peak potential follows that for the large-amplitude potential step and decays as A better fit based on an equation with two adjustable parameters... 

These results do not agree with the predominant effect of the dielectric constant reported previously. To check further, mixtures of monomer, benzene and methylene chloride were prepared, with the same computed overall dielectric constant but with different monomer contents, and the initial rates determined. The values fitted exactly on the same rate versus monomer concentration curve. Further experiments were carried out in benzene with different amounts of methylene chloride but constant initial monomer concentration. A very small amount of methylene chloride reduced the rate of noly-merization to the one determined in pure methylene chloride. The activation energies were also determined and found to be about 7.5 Reals, per mole much less than in bulk or low dielectric constant solvents. 

Fig. 3. Use of [7 P]GTP to follow GAP reaction. (A) Decrease in protein associated P induced by [325-724] AS API. Two progress curves at different [L8K]Arfl GTP concentrations are shown from an experiment in which [L8K]Arfl GTP was loaded with [7 P]GTP as described in the text. The labeled [L8K]Arfl, at final concentrations ranging from 0.5 ijlM to 10 iiM, was added to a reaction mixture containing 360 PA, 90 iiM PIP2, 0.1% (w/v) Triton X-100, and 1 nM [325-724] AS API. Samples of the reaction were taken at the indicated times following addition of [L8K]Arfl GTP and protein bound radiolabel was determined. Binding stoichiometries were determined by measuring the amount of bound nucleotide of a known specific activity. The binding stoichiometry was used to calculate the amount of Arfl GTP present. (B) Replot of initial rate data. The initial rates of loss of protein-associated P, taken to be vi, were determined from the plots in (A). The determined vis were plotted against Arfl GTP concentration. The data were fit to the Michaelis-Menten equation.

Winnik et al. [53] used time-resolved fluorescence spectroscopy (direct non-radi-ative energy transfer experiments) to determine the interface thickness in films of symmetric poly(styrene-fc-methyl methacrylate) (PS-PMMA) block copolymers labeled at their junctions with either a 9-phenanthryl or a 2-anthryl group. The corrected donor fluorescence decay profiles were fitted to simulated fluorescence decay curves in which the interface thickness 8 was the only adjustable parameter. The optimum value of the interface thickness obtained was 6 = 4.8 run. In similar studies [54—57], the same authors determined the interface thickness value 6 = 1.6 nm in mixtures of two symmetrical poly(isoprene-b-methyl methacrylate) (PI-PMMA) block copolymers of similar molar mass and composition [54] the interface thickness value 8 = 1.1 nm for the lamellar structures formed in films of symmetric PI-PMMA diblock copolymers bearing dyes at the junctions [55] a cylindrical interface thickness value of d slightly smaller than 1.0 nm in films consisting of mixtures of donor- and acceptor-labeled PI-PMMA (29vol% PI) that form a hexagonal phase in the bulk state [56] and the interface thickness 8 = 5 run on the diblock copolymer poly(styrene-l>-butyl methacrylate)(PS-h-PBMA) [57]. 

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