Aqueous gel

Balcom B J, Fischer A E, Carpenter T A and Flail L D 1993 Diffusion in aqueous gels—mutual diffusion-... 

In biological systems molecular assemblies connected by non-covalent interactions are as common as biopolymers. Examples arc protein and DNA helices, enzyme-substrate and multienzyme complexes, bilayer lipid membranes (BLMs), and aggregates of biopolymers forming various aqueous gels, e.g, the eye lens. About 50% of the organic substances in humans are accounted for by the membrane structures of cells, which constitute the medium for the vast majority of biochemical reactions. Evidently organic synthesis should also develop tools to mimic the Structure and propertiesof biopolymer, biomembrane, and gel structures in aqueous media. 

Reversible HydrocoUoids (Agar). The agar-based impression materials are thermally reversible, aqueous gels (230,231), that become viscous fluids in boiling water and set to an elastic gel when cooled below 35°C. The popularity of agar-based impression materials has diminished with the introduction of elastic impression materials such as alginate-based, polysulfide, silicone, and polyether impression materials, but agar [9002-18-0] materials are still used in substantial quantities. 

Because enzymes can be intraceUularly associated with cell membranes, whole microbial cells, viable or nonviable, can be used to exploit the activity of one or more types of enzyme and cofactor regeneration, eg, alcohol production from sugar with yeast cells. Viable cells may be further stabilized by entrapment in aqueous gel beads or attached to the surface of spherical particles. Otherwise cells are usually homogenized and cross-linked with glutaraldehyde [111-30-8] to form an insoluble yet penetrable matrix. This is the method upon which the principal industrial appHcations of immobilized enzymes is based. 

Leyden JJ, Grove G, Zerweck C (2004) A doubleblind, comparative facial tolerance study of a new 10% sodium sulfacetamide 5% sulfur aqueous gel (in a 10% urea vehicle) vs a 10% sodium sulfacetamide 5% sulfur topical suspension in rosacea acne subjects with sensitive skin. In Abstract of the 62nd Annual Meeting of the American Academy of Dermatology. Washington DC, February 6-11,2004. Abstract P66... 

Balcom, B Fischer, A Carpenter, T Hall, L, Diffusion in Aqueous Gels. Mutual Diffusion Coefficients Measured by One-Dimensional Nuclear Magnetic Resonance Imaging, Journal of the American Chemical Society 115, 3300, 1993. 

Optimization of Peak Separation and Broadening in Aqueous Gel Permeation Chromatography... 

A low-molecular-weight condensation product of hydroxyacetic acid with itself or compounds containing other hydroxy acid, carboxylic acid, or hydroxy-carboxylic acid moieties has been suggested as a fluid loss additive [164]. Production methods of the polymer have been described. The reaction products are ground to 0.1 to 1500 p particle size. The condensation product can be used as a fluid loss material in a hydraulic fracturing process in which the fracturing fluid comprises a hydrolyzable, aqueous gel. The hydroxyacetic acid condensation product hydrolyzes at formation conditions to provide hydroxyacetic acid, which breaks the aqueous gel autocatalytically and eventually provides the restored formation permeability without the need for the separate addition of a gel breaker [315-317,329]. 

Admixing a borate source with the aqueous gel formed in step 1... 

J. C. Dawson and H. V. Le. Controlled degradation of polymer based aqueous gels. Patent US 5447199,1995. 

The facilitated transfers of Na+ and K+ into the NB phase were observed by the current-scan polarography at an electrolyte-dropping electrode [12]. In the case of ion transfers into the DCE phase, cyclic voltammetry was measured at an aqueous gel electrode [9]. Both measurements were carried out under two distinctive experimental conditions. One is a N15C5 diffusion-control system where the concentration of N15C5 in the organic phase is much smaller than that of a metal ion in the aqueous phase. The other is a metal ion diffusion-control system where, conversely, the concentration of metal ion is much smaller than that of N15C5. Typical polarograms measured in the both experimental systems are shown in Fig. 2. 

Hashimoto, T., Sasaki, H., Aiura, M., and Kato, Y., High-speed aqueous gel-permeation chromatography, /. Polym. Sci. Polym. Phys. Ed., 16, 1789, 1978. 

Neddermeyer, P. A. and Rogers, L. B., Column efficiency and electrolyte effects of inorganic salts in aqueous gel chromatography, Anal. Chem., 41, 94, 1969. 

The permeability coefficient Kpcr is just the flux divided by Cw. It is apparent that the permeability coefficient is linear with P for small distribution coefficients and constant for large P. Thus, for small P the epithelium is the barrier, and for large P the stroma is the barrier. A fit for steroid permeability is shown in Fig. 12, where the regression analysis gave De = 1.4 x 10 9cm2/s and Ds = 2.0 x 10 6cm2/s for 4 = 4 x 10 3 cm and 4 = 3.6 x 10 2 cm [205]. These values for the diffusion coefficients are reasonable compared with those of aqueous gels and lipid membranes. 

This study has shown that MCC forms a gel-like structure at low solids concentration in the presence of salt. It has also been known for a considerable time (20) that MCC forms aqueous gels and pastes but at much higher solids concentration. It would appear that further studies with the MCC gel in dilute form may elucidate the mechanism of gelation more definitively. 

Heyd has studied the stability of neomycin in aqueous gels and formulated a satisfactory product by adsorbing the antibiotic on an ion exchange resin, Amberlite IRP-69M, prior to incorporation in the gel. 

Ordered body-centered cubic structures were observed by shearing aqueous gels made from anionic PtBS-PMANa block copolymer micelles [163]. The emergence of the ordered gel state could be accounted for similar building up of a polyelectrolyte-based fibrillar network that can be oriented under shear. 

Figure 2 (right). Reverse-phase HPLC elution profile of the tumor-localizing fraction of HPD isolated by non-aqueous gel exclusion chromatography. (B) Hydrolysis of this material in 50% aqueous THF containing IM HCl, at 37 °C for 24 hours. (C) After hydrolysis in IM NaOH, 50% aqueous THF under the same condition. The major porphyrins resulted are hematoporphyrin (HP), hydroxyvinyl deutero-porphyrin (HVD), and protoporphyrin (PP). 

Newkome GR, Baker GR, Aral S, Saunders MJ, Russo PS, Theriot KJ, Moorefield CN, Rogers LE, Miller JE, Lieux TR, Murray ME, Phillips B, Pascal L. Cascade molecules. Part 6. Synthesis and characterization of two-directional cascade molecules and formation of aqueous gels. J Am Chem Soc 1990 112 8458-8465. 

Make an organogel with lecithin and entrap an enzyme in the aqueous gel compartment. Can you make in this way a column for enzymatically induced chemical transformations ... 

Pirlimycin is a lincosamide recently approved by the US Food and Drug Administration for treatment of mastitis in dairy cattle (113, 114). It has excellent activity against Staphylococcus aureus, the principal organism responsible for mastitis in the dairy cow, and is administered as an aqueous gel by intramammary infusion (115). 

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