Controlled Pore Glasses

Controlled-Pore Glass. Silanol groups on the glass surface provide sites at which silanization may be performed. Silanization may be effectively performed with a 5% aqueous solution of aminopropyltri(ethoxy)silane (APTES),1 

One final activation step is required, and is the conversion of the aminophenyl group to the diazonium salt  

The diazonium salt is readily prepared from the aminophenyl group, but does not result from treatment of an aliphatic amine (such as the APTES-derivatized surface) with nitrous acid. The activated surface is now ready for enzyme coupling, since diazonium salts are very reactive toward protein tyrosine residues (Eq. 4.4)  

Although four activation steps are required prior to enzyme immobilization, this method possesses the advantages of not only providing selective covalent immobilization through tyrosines, but also of avoiding enzyme-enzyme crosslinks that can result in activity losses.4 

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The synthetic scheme typically involves chain-extending addition of protected mononucleotides to a nucleoside bound covalentiy at the 3 -hydroxyl to an inert siUca-based soHd support, such as controlled pore glass (Fig. 11). The initial base-protected 5 -O-dimethoxytrityl (DMT) deoxynucleoside is linked to the soHd support via the reaction of a siUca-bound amino-silane and the -nitrophenylester of the 3 -succinylated nucleoside, yielding a 3 -terminal nucleoside attached to the soHd support (1) (Fig. 11). Chain elongation requites the removal of the 5 -DMT protecting group. 

Supported aqueous phase (SAP) catalysts (16) employ an aqueous film of TPPTS or similar ligand, deposited on a soHd support, eg, controlled pore glass. Whereas these supported catalysts overcome some of the principal limitations experienced using heterogeneous catalysts, including rhodium leaching and rapid catalyst deactivation, SAP catalysts have not found commercial appHcation as of this writing. 

Besides shear-induced phase transitions, Uquid-gas equilibria in confined phases have been extensively studied in recent years, both experimentally [149-155] and theoretically [156-163]. For example, using a volumetric technique, Thommes et al. [149,150] have measured the excess coverage T of SF in controlled pore glasses (CPG) as a function of T along subcritical isochoric paths in bulk SF. The experimental apparatus, fully described in Ref. 149, consists of a reference cell filled with pure SF and a sorption cell containing the adsorbent in thermodynamic equilibrium with bulk SF gas at a given initial temperature T,- of the fluid in both cells. The pressure P in the reference cell and the pressure difference AP between sorption and reference cell are measured. The density of (pure) SF at T, is calculated from P via an equation of state. 

M. Thommes, G. H. Findenegg. Pore condensation and critical-point shift of a fluid in controlled-pore glass. Langmuir 70 4270-4277, 1994. 

D. Comparison of Separation by Controlled Pore Glass and Silica Gels... 

Haller, W. (1983). Application of Controlled Pore Glass in Solid Phase Biochemistry (W. Haller, ed.), pp. 535-597. Wiley, New York. 

CPG = Controlled Pore Glass (solid support) 1 and 2 (Bj, B2, B3, B4), commercially available... 

Furusawa and Yamamoto [16] studied the adsorption process of polystyrene samples (M ranging from 16700 to 2xl06) with narrow molecular weight distribution (Mw/M = 1.01-1.07) at the -conditions (cyclohexane, 35 °C). Controlled pore glass with pore diameter of 1000 A was used as an adsorbent. 

Waldmann-Meyer, H, Structure Parameters of Molecules and Media Evalnated hy Chromatographic Partition I. Controlled-Pore Glasses, Journal of Chromatography 350, 1, 1985. 

The packing material, used for the LEG work was Controlled-Pore Glass (CPG) from Electronucleonics, Fairfield, N.J. with various pore diameters similar to those used by others (6,2 ) (500-10,000 A). Each k.6 mm I.D. x 100 cm column was dry packed with the CPG of a specific pore size by tapping and vibration until a terminal, bed volume was reached. Stainless steel 20-ym frits were used on each end of the column along with the appropriate low-dead volume end-fittings. 

Experimentation with Controlled-Pore Glass involved the use of several column sets packed with the pore diameters in angstrom inits shown in Table III. 

On the other hand, Seebach and Heckel have demonstrated that sulfur-containing TADDOL derivatives could be immobilised on hydrophobic con-trolled-pore glass silica gel. Indeed, controlled-pore glass (CPG) is a rigid support that offers an openly accessible pore structure in all possible solvents... 

Since catalysts immobilised on hydrophilic silica gel often give superior performances to their polymer-bound or polymer-incorporated analogues for multiple applications, Heckel and Seebach have immobilised TADDOL derivatives on hydrophobic controlled-pore glass (CPG) silica gel. Indeed, CPG is... 

XCPS-1 Controlled pore Glass, CPG-10 (324 and 1038 A) Electronucleonics 0.05 M Na2S04 Ultraviolet absorbance (A, = 206 nm)... 

Fig. 11. Dendron 23 of 3rd generation containing 87 nucleotides. Two key intermediates in the synthesis of dendra such as 23. The box represents long-chain alkylamine controlled-pore glass [53]...

The adsorbent should have a high affinity and capacity for the enzyme and it should not absorb the reaction product or enzyme inhibitors. Among the materials used the more popular are cation and anion exchange resins, activated charcoal, silica gel, alumina, control pore glasses and ceramics. 

Haller, W., Application of controlled pore glass in solid phase biochemistry, In W.H. Scouten, ed. Solid Phase Biochemistry New York Wiley, 1983 535-597. 

The other sensor makes use of two dyes, bromophenol blue (BPB) and thymol blue (TB), to cover the range of interest26. The chromophores, immobilised on controlled pore glasses, are fixed at the end of plastic optical fibres. The distal end of the fibres is then heated and the CPGs form a very thin pH-sensitive layer on the fibre tips. The probe has four fibres (two for each chromophore) and its sketch is shown in Figure 5. A Teflon diffuse... 

Scheme 7.30 Deprotection of oligonucleotides on controlled pore glass (cpg).

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],... 

Miyake, K., Terada, H. (1982) Determination of partition coefficients of very hydrophobic compounds by high performance liquid chromatography on glyceryl-coated controlled-pore glass. J. Chromatogr. 240, 9-20. 

Van Zoonen et al. [19,20] employed an alternative approach, in an attempt to overcome the limited aqueous solubility of diaryloxalate ester-type POCL reagents. In this work, granular TCPO was mixed with controlled pore glass and packed in a flow cell, forming a solid-state TCPO reactor. When this was used in conjunction with a flow system, some of the TCPO dissolved in the carrier solution. Numerous difficulties were encountered with this approach, namely, limited reactor lifetime (approximately 8 h) and low CL emission obtained as the carrier became more aqueous (a 90% reduction of CL intensity occurred when the aqueous content of the carrier stream comprised 50% water, as compared to pure acetonitrile). The samples also required dilution with acetonitrile to increase the solubility of TCPO in the sample plug. 

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