Controlled pore glass beads

Figure 8 Separation of isomeric acids (maleic and fumaric acid) by controlled surface porosity anion exchange chromatography. Column Sulfonated fluoropolymer coated onto a 50-p glass bead. Average pore size about 1000 A. Flow rate 2.73 ml/min. Eluant 10 mM HN03. Temperature 60°C. Detection absorbance. (Reproduced from Kirkland, J. J., J. Chromatogr. Sci., 7,361,1969. By permission of Preston Publications, A Division of Preston Industries, Inc.)...

Bacillus coagulans glucose isomerase immobilized on MPS has a greater efficiency than the same enzyme immobilized on controlled pore glass. The controlled pore glass exhibits cui apparent efficiency of 0.56 relative to MPS. Pore diffusion limitations of the glass beads and bed channeling cause this inefficiency. 

MWNTs favored the detection of insecticide from 1.5 to 80 nM with a detection limit of InM at an inhibition of 10% (Fig. 2.7). Bucur et al. [58] employed two kinds of AChE, wild type Drosophila melanogaster and a mutant E69W, for the pesticide detection using flow injection analysis. Mutant AChE showed lower detection limit (1 X 10-7 M) than the wild type (1 X 10 6 M) for omethoate. An amperometric FIA biosensor was reported by immobilizing OPH on aminopropyl control pore glass beads [27], The amperometric response of the biosensor was linear up to 120 and 140 pM for paraoxon and methyl-parathion, respectively, with a detection limit of 20 nM (for both the pesticides). Neufeld et al. [59] reported a sensitive, rapid, small, and inexpensive amperometric microflow injection electrochemical biosensor for the identification and quantification of dimethyl 2,2 -dichlorovinyl phosphate (DDVP) on the spot. The electrochemical cell was made up of a screen-printed electrode covered with an enzymatic membrane and combined with a flow cell and computer-controlled potentiostat. Potassium hexacyanoferrate (III) was used as mediator to generate very sharp, rapid, and reproducible electric signals. Other reports on pesticide biosensors could be found in review [17],... 

The choice of solid carriers spans a wide spectrum (Table 1) from materials most suitable for research purposes (sintered glass beads, laterite stone deposited on a gramophone disk) to industrial materials (pumice, activated carbon, etc.). Key properties that affect the performance of the carrier are porosity (from impervious to controlled-size pores), composition (from ceramics to activated carbon), and hydrophilic behavior. It is difficult to perform a direct comparison of different carriers. Colonization and biofilm growth depend strongly on the nature of bacteria and on their intrinsic propensity to adhere on hydrophilic vs. hydrophobic surfaces. 

Some bead materials possess porous structure and, therefore, have very high surface to volume ratio. The examples include silica-gel, controlled pore glass, and zeolite beads. These inorganic materials are made use of to design gas sensors. Indicators are usually adsorbed on the surface and the beads are then dispersed in a permeation-selective membrane (usually silicone rubbers). Such sensors possess high sensitivity to oxygen and a fast response in the gas phase but can be rather slow in the aqueous phase since the gas contained in the pores needs to be exchanged. Porous polymeric materials are rarer and have not been used so far in optical nanosensors. 

Figure 2. Elution profile from columns (100 x 1.0 cm) of controlled pore glass beads of l,4-/ -linked products formed in vitro by pea membranes in 30 min. Products were dissolved in hot paraformaldehyde DMSO and eluted with DMSO in 1 ml fractions. Open circles, 1 mM UDP-[14C]glucose alone closed circles, 1 mM UDP-[14C]glucose plus 50 /iM UDP-xylose. Size markers show the molecular weight of peak elution volumes of standard dextrans, 264 = 264000 D 70 = 70000 D. (Taken with permission from Ref. 18. 1988 J. Wiley k, Sons.)...

Controlled pore glass beads (237 A mean diameter) were obtained... 

Figure 6.2 Effect of immobilization chemistry on the linewidth of compound s in solution. 1D 1 H spectra of the aromatic protons of phosphotyrosine (pY) are shown with the fitted linewidth. From top to bottom, pY in solution, in the presence of Actigel ALD, streptavidin Sepharose, Zn-IDAA Sepharose> Zn-NFA Sepharose, Zn-NFA silica and controlled-pore glass beads (for comparison).

The above list of solid supports is by no means exhaustive. Many others have been proposed and evaluated for use in peptide synthesis, including polypropylene membranes, cotton, controlled-pore glass beads, polyethylene sheets, and others. 

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