Gelatinous membrane

Gajovic et al. [64] L-malate Fruits, fruit juices, ciders and wines NAD(P)+-dependent L-malate dehydrogenase oxaloacetate decarboxylating with salicylate hydroxylase (SHL)/ in gelatine membrane sandwiched between a dialysis membrane and a PET membrane Clark-electrode ... 

Acetylcholineesterase and choline oxidase Electrode was developed by co-immobilization of AChE with ChO H202. Disposable sensors constructed by co-immobilization in a gelatin membrane on Pt electrode or by immobilizing AChE in polyurethane on a thick-film metallized Pt electrode. A kinetically controlled bioenzyme sensor was also used at a low activity of ChE for determining inhibitors. [75]... 

The potentiometric determination of estradiol-1 P in solution provides an example of a solid-phase competitive immunoassay (316). The anti-estradiol-17P antibodies are immobilized on a pig skin gelatin membrane. After incubation with HRP-labeled steroid and estradiol, the membrane is mounted over an iodide-selective electrode to measure the enzymatic activity. The electrode potential is a function of antigen concentration at levels ranging from 57 pM to 9.2 nM. 

With a gelatin membrane entrapped between two dialysis membranes and containing 46 U/cm2 of enzyme, the H2O2 formation corresponds to only 110 mU/cm2, i.e., less than 1% of the initial enzyme activity (Fig. 28). This... 

Fig. 28. Dependence of the hydrogen peroxide accumulation rate, i>2, on substrate concentration as measured in the double measuring cell depicted in Fig. 27. V2 is a measure of the apparent activity of G OD entrapped in a gelatin membrane. A membrane area of 0.13 mm2 was exposed to the measuring solution. The enzyme layer was sandwiched between two dialysis membranes. Solution 66 mmol/1 phosphate buffer, pH 7.0 25°C GOD loading 1-46 U/cm2, i.e., 6 U per electrode 2-46 mU/cm2, i.e. 6 mU per electrode.

The glucose sensor with the GOD-gelatin membrane exhibits a temperature optimum of about 40°C (Scheller et al., 1988). Below the... 

Fig. 42. Comparison of the concentration dependences of the stationary currents of glucose electrodes using gelatin membrane-entrapped GOD sandwiched between two dialysis membranes (1) and with an additional polyurethane membrane next to the solution (2).

One GOD—gelatin membrane can be used for more than 2000 measurements. These membranes have been employed in the Glukometer GKM glucose analyzer (ZWG Berlin, GDR). 

Wollenberger et al. (1986) proposed the elimination of interfering substances by using laccase in a glucose sensor. The electrode involved a layer of coimmobilized GOD and laccase in a gelatin membrane. 

Weigelt et al. (1987a) optimized an LMO-gelatin membrane for application in the Glukometer analyzer (ZWG, GDR). The enzyme loading test (Fig. 56) shows that above 1 U/cm2 the sensor is diffusion controlled,... 

With a constant of K = 2.7640-5 mol/1 (pH 7.0, 25°C) the equilibrium of the LDH-catalyzed reaction lies far to the lactate side. This means that whereas for lactate sensors based on LDH the forward reaction has to be forced by alkaline buffer and pyruvate- or NADH-trapping agents, the reduction of pyruvate proceeds spontaneously under normal conditions. This direction of the reaction has been used in a sequence electrode for pyruvate assay (Weigelt et al., 1987b). In the presence of lactate monooxygenase (LMO) lactate formed from pyruvate by LDH is oxidized by molecular oxygen, the consumption of which was indicated at a Clark-type electrode. The enzymes were immobilized in a gelatin membrane. Of course such a sensor measures the concentration of lactate in the sample, too. Therefore it is suited to the determination of the lactate/pyruvate ratio, which is a clinically important parameter. Pro-... 

The principle of enzymatic amplification can be drastically simplified by conducting the two partial reactions of the cycle with only one enzyme. Using this approach, Schubert et al. (1990) developed an LDH sensor for NADH determination. The enzyme was immobilized in a gelatin membrane and coupled to an oxygen probe, where it catalyzes the oxidation of NADH by pyruvate ... 

In-process verification of the sterility of filtered gases may be done by constantly bleeding off a trickle of gas through a pressure reducer on the downstream side of the sterilizing filter. The bleed may be filtered through a gelatin membrane, which should be removed daily or at other suitable intervals for incubation and examination for evidence of microbiological contamination. 

With a gelatin membrane entrapped between two dialysis membranes and containing 46 U/cm of enzyme, the H2O2 formation corresponds to only 110 mU/cm, ie, less than 1% of the initial enzyme activity (Figure 14-19). This indicates a large excess of enzyme in the membrane. Consequently, the membrane is diffusion controlled. The low apparent activity may be attributed mainly to the diffusion resistance of the dialysis membrane for glucose. On the other hand, the measured activity of the membrane containing 46 U/cm is already about 70% of the activity used for immobilization. This value approaches that expected for pure kinetic control of the process [287], The apparent activity of urease immobilized in a cellulose triacetate membrane was found to be 66% of the initially applied enzyme activity [288]. 

It then appears from the behaviour with respect to very dilute solutions of basic dyes that in a number of the objects the gelatin membrane does in fact completely enclose the cavity filled with gum arabic solution. In these objects the dye is intensely accumulated in the vacuole and can even bring about coacervation of the gum arabic inside it (see p. 467, 5a). 

The high mechanical strength in the wet state, substantial permeability for liquids and gases and low irritation of skin indicate that the gelatinous membrane of BC will be... 

MC produced by the vinegar fermentation bacterium A. xylinum is synthesized in the form of twisting ribbons, which in stationary culture forms a thick, gelatinous membrane on the surface of a liquid medium. The membrane formed in such conditions is characterized by the 3D structure made of an ultrafine network of... 

D. Jain, E. Carvalho, A.K. Banthia, and R. Banerjee, Development of polyvinyl alcohol-gelatin membranes for cuitibiotic dehvery in the eye. Drug Dev Ind Pharm, 37,167-177,2011. 

Fadnavis, N.W., Koteshwar, K. 1999. An unusual reversible sol-gel transition phenomenon in organogels and its application for enzyme immobilization in gelatin membranes. Biotechnol. Prog. 15, 98-104. 

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