Cross-linked polyacrylamide

Alcosorb 400 Water-Retaining Polymer," undated product Hterature, AHied CoUoids describes agricultural uses of cross-linked polyacrylamide gels. 

Cross-linked polyacrylamides attached with morpholine pendent at some repeating unit of the backbone chains have been prepared and used for the separation of discrete chemical compounds by gel-permeation chromatography (83). 

Hjerten, S. and Mosbach, R., Molecular sieve chromatography of proteins on columns of cross-linked polyacrylamide, Anal. Biochem., 3, 109, 1962. 

Heiger, D. N., Cohen, A. S., Aharon, S., and Karger, B. L., Separation of DNA restriction fragments by high performance capillary electrophoresis with low and zero cross-linked polyacrylamide using continuous and pulsed electric fields,. Chromatogr., 516, 33, 1990. 

Widhalm, A., Schwer, C., Blaas, D., Kenndler, E. (1991). Capillary zone electrophoresis with a linear, non-cross-linked polyacrylamide gel separation of proteins according to molecular mass. J. Chromatogr. 549, 446 451. 

Inman, J.K., and Dintzis, H.M. (1969) The derivatization of cross-linked polyacrylamide beads. Controlled introduction of functional groups for the preparation of special-purpose, biochemical adsorbents. Biochemistry 8, 4074-4082. 

Capillary gel electrophoresis (CGE) is a specialised form of CE that employs a fused silica capillary filled with an immobilised and cross-linked polyacrylamide gel. This gel contains a network of pores, which allows separation of ions based on differences in molecular size. CGE was applied to the separation of ionic alkylphenol ethoxy sulfates and... 

Many commercially important polymers are produced via emulsion polymerization. This is also one of the most common methods to produce dye-doped beads. A dye is added to the mixture of monomers prior to initiating the polymerization and is either noncovalently entrapped or is copolymerized. The second method ensures that no leaching will occur from the particle but requires modification of the dye (typically by providing it with a double bond). This method is most common for preparation of pH-sensitive beads where a pH indicator is entrapped inside cross-linked polyacrylamide particles. The size of the beads can be tuned over a wide range so that preparation of both nano- and microbeads is possible. Despite thorough washing the surfactants are rather difficult to remove completely and their traces can influence the performance of some biological systems. 

Figure 8.2 Polyacrylamide gel formation and hydrolysis of acrylamide to acrylate. (A) Acrylamide and A,A-methylenebisacrylamide (bis) are copolymerized in a reaction catalyzed by ammonium persulfate [(NH4)2S208] and TEMED. (B) A very short stretch of cross-linked polyacrylamide is represented. Cross-linking between similar structures leads to the formation of ropelike bundles of polyacrylamide that are themselves cross-linked together forming the gel matrix. In the lower portion of (B) is shown how pendant, neutral carboxamide groups can become hydrolyzed to charged carboxyls.

Three main types of polymer-based monoliths are polymethacrylate-based monoliths where methacrylate forms the major component of the monomers for polymerization, polyacrylamide-based monoliths where cross-linked polyacrylamide is synthesized directly within the capillary, and polystyrene-based monoliths that are usually prepared from styrene and 4-(chloromethyl) styrene as monomers and divinylbenzene (DVB) as the cross-linker. 

Polymer Network Studies Using Piiramagnetic Probes Cu(II) in Cross-Linked Polyacrylamide Gels... 

Figure 1. ESR spectra of Cu(II) at X-band and 77 K in chemically cross-linked polyacrylamide gels with pore diameters of 1.3 nm (A) and 4.0 nm (B). Solid lines are experimental spectra dotted lines are spectra calculated using the appropriate values of AH, and given in Table I and with 2.408, gj = 2.080, A,= 0.0134 cm, Aj,= 0.0009 cm, and AH = 30.0 Gauss.

Figure 5. ESR spectra of Cu(II) at X-band in chemically cross-linked polyacrylamide gels with pore diameter of 0.7 nm as a function of temperature. The appearance of the quartet centered g-iso is visible above 245 K.

In CGE the capillary is filled with a gel containing cross-linked or linear polymers. The gel thereby acts as molecular sieve. Traditionally, cross-linked polyacrylamides and agarose have been utilized in the slab and tube format. Polyacrylamides when cross-linked have smaller pore sizes and are used for protein separations. The larger pore sizes of agarose gels are more suitable for DNA separation. Polyacrylamides yield very viscous gels. Therefore, polymerization is usually done on column, which has a lot of practical problems. 

Shea KJ, Stoddard GJ, Shavelle DM, Wakui F, Choate RM. Synthesis and characterization of highly cross-linked polyacrylamides and polymethacrylamides—a new class of macro-porous polyamides. Macromolecules 1990 23 4497-4507. 

FIG. 12.12 Electrophoresis patterns for human serum (a) schematic of schlieren profiles and (b) semilog plot of protein molecular weight versus electrophoretic mobility for particles electro-phoresed on cross-linked polyacrylamide. (Reprinted with permission from K. Weber and M. Osborn, J. Biol. Chem., 244, 4404 (1969).)... 

Figure 12.12b illustrates the application of gel electrophoresis to protein characterization. In this illustration a cross-linked polyacrylamide gel is the site of the electrophoretic migration of proteins that have been treated with sodium dodecyl sulfate. The surfactant dissociates the protein molecules into their constituent polypeptide chains. The results shown in Figure 12.12b were determined with well-characterized polypeptide standards and serve as a calibration curve in terms of which the mobility of an unknown may be interpreted to yield the molecular weight of the protein. As with any experiment that relies on prior calibration, the successful application of this method requires that the unknown and the standard be treated in the same way. This includes such considerations as the degree of cross-linking in the gel, the pH of the medium, and the sodium dodecyl sulfate concentration. The last two factors affect the charge of the protein molecules by dissociation and adsorption, respectively. Example 12.5 considers a similar application of electrophoresis. 

EXAMPLE 12.5 Estimation of Number of Nucleotides in Glycine tRNA Using Electrophoresis. Synthetic DNA standards and RNA molecules were electrophoresed in 7 M urea solution on cross-linked polyacrylamide gels (Maniatis et al. 1975). A semilog plot of the number of nucleotides versus the mobility relative to xylene cyanol FF dye is linear and includes the points (N = 100, u i = 0.33) and (N = 50, urei = 0.55). Estimate the number of nucleotides in the glycine tRNA molecule of Staphylococcus epidermidis if it shows a relative mobility of 0.16. 

Polyurethane Hydrogel Cross-Linked Polyacrylamide Gels Cross-Linked Polyacrylic Acid Gels... 

Premixed blends of acrylamide and bisacrylamide prepared with varius ratios of monomers were purchased from Eastman Kodak Chemical Company (Rochester, NY). The 37.5 1 and the 19 1 preparations were used for the study. Gels made from these mixtures will be referred to as 2.6% and 5% cross-linked polyacrylamides, respectively. Five grams of each monomer blend were added to 95-g portions of distilled water. Solution was achieved by mixing for 1 h. To each sample was added 1 ml each of a 1% solution of N, N, N, N -tetramethylethylenediamine (Eastman Chemical Co., New Haven, CT) and a 10% solution of ammonium persulfate (Mallinckrodt Laboratory Chemicals, Phillipsburg, N.1). The solutions were poured into an open polyethylene mold and allowed to cure for 12 h at room temperature. The gels were carefully removed and placed in an excess of distilled sterile water for 48 h. The water was replaced several times during the equilibration period. It was felt that this was sufficient to remove unreacted monomers and impurities. The gels were then cut with a steel-ruled die into circles 40 imn in diameter. 

Figure 2.5. Typical components of cross-linked polyacrylamide supports for solid-phase synthesis.

LCAA LC-MS LDA Leu Lys Macrosorb long chain alkylamine spacer liquid chromatography coupled with mass spectrometry lithium diisopropylamide S-leucine S-lysine cross-linked polyacrylamide adsorbed onto kieselguhr... 

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