Determination by electrophoresis

FIG. 12.13 Net charge of egg albumin versus pH. The points were determined by electrophoresis, and the solid line by titration the broken line represents 60% of charge from titration. (Data from L. G. Longsworth, Ann. NY Acad. Sci., 41, 267 (1941). (Redrawn with permission from J. Th. G. Overbeek, Quantitative Interpretation of the Electrophoretic Velocity of Colloids. In Advances in Colloid Science, Vol. 3 (H. Mark and E. J. W. Verwey, Eds.), Wiley, New York 1950.)... 

As previously discussed in this chapter, the molecular size of protein or nucleic acid samples may be determined by electrophoresis. This requires the preparation of standard curves of log molecular weight versus fi (mobility) using standard proteins or nucleic acids. 

Akhtar and Lai128) infer the adsorption mechanism of a collector on a mineral surface from the mutual position of IPpH and PZC which they determine by electrophoresis. Their deduction is based on experiments performed with hematite in solutions of Na oleate (NaOl) and dodecylamine hydrochloride (DDA-HC1). The surface of hematite is assumed to consist of MeOHj, MeOH and MeO-. Chemisorption of the collector is discussed according to Table 3 which is based on Eq. 72 for charge density at the inner Helmholtz plane ... 

The numerical solution for the surface potential as a function of pH is compared in Fig. 7, for various NaCI concentrations, with the experimental results provided by Li and Somasundaran [32], The potentials — ]i,s = — ]i(0) and — tyd= — t)t(t/E) are plotted as functions of distance, since the zeta potential determined by electrophoresis is not defined at the surface, but at an unknown location, the plane of slip . The magnitude of <-s is always larger than that of i >d, since the potential decays with the distance. The value dE=4 A, which is provided by the dependence of the surface tension of water on the NaCI concentration at high ionic strengths was employed. For the equilibrium constant, the value K ou= () 10 M, which is consistent with the experimental data for pH values between 3 and 6, was selected. A reasonable agreement with the data (which have a rather large error) was obtained by selecting A=5.0X 1016 sites/m2 and W1 = 0.5kT. 

Figure 8.26 PolyP chain lengths in mutant strains determined by electrophoresis in PAGE (Sethura-man et al., 2001). Cells were grown in a synthetic medium containing 7.35 mM P, WT, parent strain ppxlA, mutant with inactivated PPX1 gene ppnl A, mutant with inactivated PPN1 gene ppxlA ppnl A, double-mutant.

FIG. 24 Relationship between the surface chemistry and the electrochemistry of commercial and chemically pretreated carbon blacks (a) correlation between the concentration of acidic functional groups (determined by titrations) and zeta potential (determined by electrophoresis) (b) conelation between zeta potential and the slurry pH. (Adapted from Ref. 629.)... 

The dynamic mobility which is determined by the electro-acoustic effects differs from the low-frequency or DC mobility that is determined by electrophoresis... 

The microspheres mentioned above are all spherical and no change of the diameter and aggregation of the microspheres takes place during the reaction of surface modification. The surface charge of every microsphere can be determined by electrophoresis. For instance, the zeta potentials of our cellulose triacetate, Cell-OH, crosslinked Cell-OH, Cell-CM, Cell-SE, Cell-NHa, Cell-DEAE, Cell-DEAE(Me), and benzyl cellulose microspheres were —19.9, —2.1, —2.7, —17.1, —20.9, +4.6, +14.2, +15.1, and —65.2 mV, respectively. This result indicates that anionic and cationic microspheres with the same average diameter but different surface charges can be prepared by this method. 

Table 3.1 summarizes the radiochemical purity, determined by electrophoresis, of the reaction mixtures prepared with different molar peptide to radionuclide ratios. Figure 3.1 shows the various HPLC profiles that were observed for the different molar peptide to radionuchde ratios. 

Note n = 3 stability determined by electrophoresis. Refrigerated storage. 

The Chi a-containing, core antennas CP47 and CP43 that are most closely associated with the reaction center (CP stands for chlorophyll protein, the number referring to the molecular mass of t h e complex in kDa, usually determined by electrophoresis). 

The support, zirconia (ISA), was supplied by the Norton Company. The oxide was grounded and sieved to a particle size ranged from 0.16 to 0.25 mm, and calcined at 773 K. Its surface properties, 63.3 m g of specific surface and average pore diameter of 8.60 nm, were determined from the nitrogen adsorption isotherms. The catalysts were prepared by adsorption from solution and/or impregnation of precursor(s), ruthenium nitrosyl nitrate (Alfa) and hexachloroplatinic acid (Aldrich), onto the support. Being zirconia isoelectric point 6.5 (determined by electrophoresis [17] using a Malvern Instrument Zetasizer 4) the precursors solution pH value was kept sufficiently low to enable the desired adsorption of complex metal anions. 

A final point to be dealt with is the achievement of specificity with the Ti02/Pt catalyst. As was illustrated above, these particles interact selectively with MV-+ while no or very slow reaction occurs with Ru(bipy)2+. This effect is readily interpreted in terms of the positive surface charge of the particles. The Ti02 particles prepared from hydrolysis of titanium isopropoxide when charged with Pt have an isoelectric point of 3 as determined by electrophoresis technique. At pH = 1.5 employed in or experiments, the surface is positively charged (f = 28 mV). Thus the access of Ru(bipy)3+ to the particle surface is impaired by electrostatic forces which explains its astonishingly long lifetime under these conditions. 

The oxides used in this study were a-Si02 (a-quartz), obtained commercially, and a-FeOOH (goethite), which was prepared in a manner similar to that of Forbes et al. (18). The silica was washed initially in Q.IN nitric acid. Both oxides were washed with double distilled water, dried at 100°C for 24 hr, powdered with a mortar and pestle, and passed through a 200 mesh (75 /xm) sieve. Powdered x-ray diffraction verified the existence of a-quartz and goethite. BET-Ng adsorption indicated specific surface areas of 1.7 m /g for silica and 85 m /g for goethite. Corresponding ZPC values, determined by electrophoresis and turbidity measurements, were 1.7 and 5.5. Dielectrics were taken to be 4.3 for silica and 14.2 for goethite (19). 

Figure 1. Dependence of specific rotation at 313 nm on pH value, BSA in 0.02 M thiocyanate. Distribution of N and F components as determined by electrophoresis shown in upper dashed line, results of perturbation difference spectra in lower broken line. From Leonard and Foster (1%1).

FIG. 6 Effect of atmospheric exposure on the isoelectric point (determined by electrophoresis) and point of zero charge (determined by mass titration) for an activated carbon treated in H2 at 950°C. 

Townsend DE, Sparkes RS, Baluda MC, McClelland G (1970) Unicellular histogenesis of uterine leiomyomas as determined by electrophoresis by glucose-6-phosphate dehydrogenase. Am J Obstet Gynecol 107 1168-1173... 

The integrity of the RNA, as indicated by the presence of 28S and 18S RNA bands, is determined by electrophoresis of 1 pL on a 1 % w/v agarose gel (Fig. 3) Quantify total RNA by spectrophotometry at 260 nm using 1 pL diluted with 99 pL water, and a small quartz cuvet We generally obtain a total yield of 40-80 pg per sample. At 20 pg/lane on the agarose gel, this is enough to generate several blots (see Note 5)... 

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