Polyacrylamide-type phases

Another type of chiral phase based on hydrogen-bonding interactions is the polyacrylamide-type phases. Developed by Blaschke, the phase is comprised of a polyacrylamide that incorporates phenylalanine ethyl ester. The phase has a helical structure, and the interactions are based on hydrogen bonding between the polar groups of the enantiomer and the CO—NH groups of the polymer [43,44]. 

The drag-reducing properties of a polyacrylamide type were tested in two-phase air/water flow, using a horizontal pipe of 31-nun diameter [1545]. The properties of the polymer were tested in single-phase water flow, and the results were found to comply with the reduction in pressure drop found by other workers. Positive effects in two-phase flow were found to depend on the Reynolds... 

Based on the principle of the equal and simultaneous solvation of the polymer and the bound peptide chains in different solvents, Sheppard and coworkers developed a number of polyacrylamide-type supports for solid phase peptide synthesis 50 55). In this case, the crosslinked polymeric support, in addition to possessing the good mechanical characteristics like polystyrene, is much more structurally related to the peptide than in the case of polystyrene. The polar polyacrylamide support in this case is prepared by the emulsion copolymerization of a mixture of dimethylacrylamide (7), ethylenebisacrylamide (2) and acryloylsarcosine methylester (5), initiated by ammo-nium persulphatesl). 

Such polyacrylamide type CSPs are best operated under normal-phase conditions (usually u-hexane with a polar modifier like alcohols, dioxane, THF, etc.). The spectrum of applicability includes a wide variety of drug substances with hydrogen donor-acceptor and aromatic groups. Other groups also prepared CSPs from chiral (meth)acrylamide monomers with various chiral amino components. An extensive review on this topic was published by Kinkel 47j. 

Development research on the DDS that uses phase transition of gels has been actively performed with thermoresponsive gels. Significant results have been reported for the development of base gel materials and the drug delivery system that use these gels. Although in vitro research is now underway, actual applications will become possible in the future. Polyacrylamide type polymers are thermoresponsive. As shown in Table 2, polymers that possess wide transition temperatures have been discovered. Under phase transition temperature the polymers will swell and above the transition they will shrink. 

The materials originally used as stationary phases for GPC were the xerogels of the polyacrylamide (Bio-Gel) and cross-linked dextran (Sephadex) type. However, these semi-rigid gels are unable to withstand the high pressures used in HPLC, and modern stationary phases consist of microparticles of styrene-divinylbenzene copolymers (Ultrastyragel, manufactured by Waters Associates), silica, or porous glass. 

In actual practice, the inert gels of dextran (I)-a polyglucose or other types of polymers, for instance agarose and polyacrylamides, wherein the macromolecules invariably are cross-linked to afford a reasonably porous 3D-structure, served as the stationary phases in size-exclusion chromatography. 

The methods for each study are divided into the initial protein separation step, a second separation step if applicable, the type of mass analysis, and the software used for peptide identification. ID = one dimensional polyacrylamide gel electrophoresis, 2D = two dimensional polyacrylamide gel electrophoresis, MS = mass spectrometry (peptide mass fingerprinting), MS/MS = tandem mass spectrometry, MALDI-TOF = matrix assisted laser desorption/ionization-time of flight, MS FIT = software from Protein Prospector, http //prospector.ucsf edu/, ESI = electrospray ionization, Q-TOF = quadrupole-time of flight, PPSS2 =Protana s Proteomic Software Suite (ProtanaEngineering, Odense, Denmark), Mascot = Matiix Science, http //www.matrixscience.com/, TOF-TOF = MALDI plus TOF tandem mass spectrometry, RP-HPLC = reverse phase high performance liquid chromatography, Q-IT = quadrupole ion trap, LIT = linear ion trap. Bioworks = Thermo Electron Corporation. 

A CSP consists of a chiral selector, which either alone constitutes the stationary phase or which has been immobilised to a solid phase. The chiral selector is a low molecular weight compound or a polymer, either synthetic or natural. A broad range of CSPs has been developed. Examples of CSPs that have been used successfully include polysaccharides, such as cellulose and its derivatives [6] and cyclodex-trins [7], and proteins, e.g. bovine serum albumin, aj-acid glycoprotein, cellulase, trypsin and a-chymotrypsin [8]. Several different synthetic polymers have also proven to be useful CSPs, for example the Blaschke-type CSPs (polyacrylamides and polymethacrylamides) [9] and the Pirkle-type CSPs [10]. 

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