Dextran detection methods

Figure 1. Conventional immunohistochemical detection methods. Florseradish peroxidase (HRP) and alkaline phosphatase are commonly employed as enzymes for visualization with chromogen. A The polymer -based method in which dextran polymer is commonly used. B Streptavidin/biotin reaction-based methods including the labeled streptavidin (LSAB) and streptavidin-biotin complex (sABC) methods.

Detection methods in gel filled capillaries are most commonly UV-absorption and laser induced fiuorescence. Proteins have a high UV-absorbance at k = 200 nm and X = 214 nm. Polyacrylamide gels absorb strongly at k < 230 nm and are, therefore, not suitable for protein analysis. Dextrane or PEG can be used as alternatives, as they are both UV-transparent. The absorption of DNA fragments is usually measured at k = 260 nm (see section 1.3.3.1), for which PA gels are well suited. 

The formation of a boundary between the dextran solution and the dextran solution containing PVP 360 (concentration 5 kg m 3) yields an apparently normal Gaussian distribution of the material detected by Schlieren optics. The various apparent diffusion coefficients obtained by an analysis of the Schlieren curves, which include diffusion coefficients obtained by the reduced height-area ratio method, the reduced second-moment and the width-at-half-height method, show the same qualitative behavior although quantitative differences do exist. This is seen in Fig. 7 where the... 

In a method of capillary electrophoresis, 1 pg of dextran was dispersed in alkaline buffer containing fluorescein, and the dextran was detected by negative fluorescence (Richmond and Yeung, 1993). 

In PVA-coated capillaries it was possible to separate at pH 2.5 the standards of poly-2-vinylpyridinium hydrochloride (p(2-VPy)) in the molecular mass range between 1500 and 1,730,000 g mol-1 with dextran T70 as sieving matrix [20]. An example is shown in Fig. 4, where a 5% solution of dextran T70 has been used. The efficiency of the monomolecular basic marker 4-aminopyridine is excellent, demonstrating the exclusion of secondary adsorptive effects at the capillary surface. Hence, the broad peaks of the polymeric standards are due to their polydispersity. As in CE the width of the peaks depends on their migration velocity through the detection window, no direct comparison of broadness of the individual peaks and analyte polydispersity is possible. However, for each individual peak the methods applied in SEC for calculation of the different molecular mass averages can be applied. 

Microbial polysaccharides from Xanthomonas campestris, notably xanthan gum for use in food industry, have been studied. Other polysaccharides like dextrans, pullulans, scleroglucan were isolated from several microbial sources. Incorporation of xanthan gum in traditional Indian fermented foods like Idli and Dosa has been investigated in elaborate details. Other products with supplementation of xanthan gum which have been investigated include orange and lemon squash, commercial tomato soup, yogurt preparations with or without CMC. Immunological methods for detection of xanthan gum in... 

T3. Thorpe. S. M., Monoclonal antibody technique for detection of estrogen receptors in human breast cancer Greater sensitivity and more accurate classification of receptor status than the dextran-coated charcoal method. Cancer Res. 47, 6572-6575 (1987). 

Sonnemann et al. (4) used both scrape loading and electroporation to successfully load cells with fura-2-dextran and measure [Ca ], changes in response to 0.1-1 pM cAMP. The results were in conflict to findings reported previously by Schlatterer et al. (5, 24), who scrape loaded cells with fura-2-dextran and reported no detectable change in [Ca +], after stimulation with submicromolar concentrations of cAMP. These contradictions may reflect the technical difficulties which are encountered when loading Dictyostelium cells with fluorescent Ca -sensitive indicators using either of these two methods. 

There were also attempts to calibrate the SEC columns with help of broad molar mass dispersity poplymers but this is less lehable. The most common and well credible SEC cahbration standards are linear polystyrenes, PS, which are prepared by the anionic polymerizatioa As indicated in section 11.7, according to lUPAC, the molar mass values determined by means of SEC based on PS calibration standards are to be designated polystyrene equivalent molar masses . Other common SEC calibrants are poly(methyl methaciylate)s, which are important for eluents that do not dissolve polystyrenes, such as hexafluoroisopropanol, further poly(ethylene oxide)s, poly(vinyl acetate)s, polyolefins, dextrans, pullulans, some proteins and few others. The situation is much more complicated with complex polymers such as copolymers. For example, block copolymers often contain their parent homopolymers (see sections 11.8.3, 11.8.6 and 11.9). The latter are hardly detectable by SEC, which is often apphed for copolymer characterization by the suppliers (compare Figure 16). Therefore, it is hardly appropriate to consider them standards. Molecules of statistical copolymers of the same both molar mass and overall chemical composition may well differ in their blockiness and therefore their coils may assume distinct size in solution. In the case of complex polymers and complex polymer systems, the researchers often seek support in other characterization methods such as nuclear magnetic resonance, matrix assisted desorption ionization mass spectrometry and like. 

A sensitive method for the estimation of different surface active compounds (tetraalkylammonium salts, dextrans, crude oil components) in water is based on the measurements of the depression of the electrocapillary curve under conditions where the transport of the compound to the dropping Hg-electrode is accelerated by stirring of the solution being examined[12] The detection limit is in the range of 10-100 jjg 1 More details on "adsorptive polarographic analysis" are given in[13]. 

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