Polyacrylamide surfaces

FIGURE 3.4 CCD images of 100 pM rhodamine B in water obtained at the intersection of a side-arm channel with a main channel on a microchip, applying a positive potential at the top channel relative to the side arm and using (a) all native glass surfaces, and (b) a native glass main channel and a linear polyacrylamide surface coated side-arm channel [816]. Reprinted with permission from the American Chemical Society. 

Figure 8. Plot of contact angle data illustrating great disparity in the wetting of a polyacrylamide surface by liquids capable of sensing different surface...

Figure 4. Cos e vs. y vo for various pure liquids on polyacrylamide surfaces...

In the case of Fe304/PAA nanocomposites, covalent binding of Ig was carried out after activation of polyacrylamide surface with ethylenediamine to form reactive —NH2 groups ... 

Directions for preparing a potentiometric biosensor for penicillin are provided in this experiment. The enzyme penicillinase is immobilized in a polyacrylamide polymer formed on the surface of a glass pH electrode. The electrode shows a linear response to penicillin G over a concentration range of 10 M to 10 M. 

Polyacrylamide, whether charged or not, can be detected by reactions of the amide group (67,68) however, a number of substances can interfere with the determination. If the molecular weight is high enough, flocculation of a standard slurry of clay or other substrate is a sensitive method for detecting low levels of polyacrylamide (69). Once polymers are adsorbed on a surface, many of these methods caimot be used. One exception is the use of a labeled polymer. 

The substantial decrease of polyacrylamide solution viscosity in mildly saline waters can be uti1i2ed to increase injection rates. A quaternary ammonium salt polymer can be added to the polyacrylamide solution to function as a salt and reduce solution viscosity (144). If the cationic charge is in the polymer backbone and substantially shielded from the polyacrylamide by steric hindrance, formation of an insoluble interpolymer complex can be delayed long enough to complete polyacrylamide injection. Upon contacting formation surfaces, the quaternary ammonium salt polymer is adsorbed reducing... 

The enzyme can be immobilized on the electrode by several techniques (53). The simplest method, first used in 1962, is to trap an enzyme solution between the electrode surface and a semipermeable membrane. Another technique is to immobilize the enzyme in a polymer gel such as polyacrylamide which is coated on the electrode surface. Very thin-membrane films can be obtained by electropolymerization techniques (49,54,55) using polypyrrole, polyindole, or polyphenylenediamine films, among others. These thin films (qv) offer the advantage of improved diffusion of substrate and product that... 

Plus One REPEL-SILANE ES (a solution of 2% w/v of dichloromethyl silane in octamethyl cyclooctasilane) is used to inhibit the sticking of polyacrylamide gels, agarose gels and nucleic acids to glass surfaces and is available commercially (Amersham Biosciences). 

The described bioaffinity separations demonstrate that polyacrylamide spacers aid the selective binding of highly complex and delicate biomacromolecules and their associates. Moreover, these solutes remain biologically active after desorption probably due to the high inertness and flexibility of the surrounding polymer chains fixed on the solid support. The unbound parts of serum usually show no loss of the activities of their constituents. Thus we evaluate the surface of inorganic supports coated with chemisorbed iV-hydroxyethyl polyacrylamide and its derivatives as being biocompatible. 

Exacting control of buffer preparation and the characteristics of capillaries and coatings is now recognized as key to successful electrophoretic separations.2 Repeatability of separations requires standardized surface preparation and rinse procedures. For example, capillaries can be coated with polyacrylamide using thionyl chloride surface activation. This approach was useful in DNA analysis.3 Non-aqueous buffers can be used to permit the use of thicker capillaries and higher voltages.4... 

Another approach has been to immobilize proteins within arrays of microfabricated polyacrylamide gel pads (Arenkov et al., 2000). Nanoliters of protein solutions are transferred to 100 x 100 x 20-pM gel pads and assayed with antibodies that are labeled with a fluorescent tag. Antigen imbedded in the gel pads can be detected with high sensitivity and specificity (Arenkov et al., 2000). Furthermore, enzymes such as alkaline phosphatase can be immobilized in the gel pads and enzymatic activity is readily detected upon the addition of an indicator substrate. The main advantage of the use of the threedimensional gel pad for fixation of proteins is the large capacity for immobilized molecules. In addition, the pads in the array are separated from one another by a hydrophobic surface. Thus, each pad behaves as a small test tube for assay of protein-protein interactions and enzymatic reactions (Arenkov et al., 2000). The disadvantage of the method is the need to microfabricate the array of gel pads in that microfabrication is... 

Flocculants cause colloidal clay particles to coagulate thus promoting separation from the drilling fluid which has been circulated down the wellbore and returned to the surface. The treated fluid may then be pumped back down the well bore. Sodium chloride, hydrated lime, gypsum, sodium tetraphosphate, polyacrylamide, poly(acrylamide-co-acrylic acid), cationic polyacrylamides, and poly(ethylene oxide) have been used commercially. 

Compared to partially hydrolyzed polyacrylamide, xanthan gum is more expensive, more susceptible to bacterial degradation, and less stable at elevated temperatures (1). However, xanthan gum is more soluble in saline waters, particularly those containing divalent metal ions generally adsorbs less on rock surfaces and is substantially more resistant to shear degradation (1,34). The extensional viscosity of the semi-rigid xanthan molecule is less that that of the flexible polyacrylamide (263). 

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