Membrane thickness buffer

Tables I-III contain a summary of the response time data as a function of the membrane thickness, the glucose oxidase loading, and the flowrate of buffer solution through the flow cell. The reproducibility of the experiments is indicated by the replicated data points in Tables I-III. The deviations in some cases are large and may be due to unduplicated folds in the membrane when assembled in the flow cell and possible membrane motion or fluttering, especially at higher flowrates during an experiment (5).

Acetylcholineesterase and choline oxidase Enzymes were co-immobilized on chemically preactivated immun-dyne polyamide membrane (thickness 120 pm, size cut-off 3 pm). Applying 20 pL of 1% ChO solution in 0.1 M-phosphate buffer (pH 6). Assay was based on electrochemical detection of the generated h2o2. The response time was 2min. Detection limit was 50 nM and the response was rectilinear up to 20 pM. [71]... 

The absorbance of bacteriorhodopsin at the experimental concentrations (40-50 mg/mL) varied between 0.6 and 0.8 in a 1-mm-thick cell at 198 nm, which allowed a correct CD measurement down to this wavelength. Transmembrane potentials were maintained by K+ gradients across the membrane in buffer solutions (7) as follows. 

Third, aminoacylase was adsorbed in multilayers based on an ion-exchange interaction with the graft chains extending from the pore surface due to their electrostatic repulsion. A solution of aminoacylase dissolved inTris-HCl buffer (pH 8.0) was fed to the inside surface of the DEA-EA fiber. The solution was allowed to permeate through the pores across the membrane thickness at a constant flow rate of 60 mL/h. From the determination of the change in enzyme concentration of the effluent with effluent volume penetrating the hollow fiber, the amount of enzyme adsorbed was calculated as 190 mg per gram... 

In addition to the effect of the retardation factor, / , expressed in Eqs. 4 and 5, other factors such as buffer diffusivity within the hydrogel and the hydrogel membrane thickness (affected by hydration) affect the pH-dependent response. The hydration, //, may be analytically described by a Henderson-Hasselbalch titration... 

The equations used to calculate permeability coefficients depend on the design of the in vitro assay to measure the transport of molecules across membrane barriers. It is important to take into account factors such as pH conditions (e.g., pH gradients), buffer capacity, acceptor sink conditions (physical or chemical), any precipitate of the solute in the donor well, presence of cosolvent in the donor compartment, geometry of the compartments, stirring speeds, filter thickness, porosity, pore size, and tortuosity. 

Electrotransfer from a gel to a membrane is done by directing an electric field across the thickness of the gel to drive proteins out of the gel and on to the membrane. There are two types of apparatus for electrotransfer (1) buffer-filled tanks and (2) semidry transfer devices (Figure 8.12). 

Figure 27. Plots of the permeation current density vs. the square root of the Tafel reaction current density [Eq. (33)], recorded in ace-tate/acetic acid buffers at pH = 6 and 30°C, using carbon steel membranes of 1.0 and 0.5 mm thickness. ...

The carrier used for this purpose consisted of a 0.1 M phosphate buffer of pH 7. The appearance of the sensing microzone is shown in Fig. 5.5.B. The oxygen optrode used was based on a 10-pm silicone rubber film containing dissolved decacyclene as indicator (S) that was fixed on a 110-pm thick polyester support (PS). A 9-pm black PTFE membrane (I) was used for optical insulation. The dye fluorescence was found to be markedly dependent on the concentration of oxygen, which exerted a quenching effect on it. The enzyme (glutamate oxidase) was immobilized on a 150-pm thick immunoaffmity membrane (E). The sensor was prepared similarly as reported by Trettnak et al. [7]. 

Remove the gel from the electrophoresis apparatus, and remove any stacking gel that may be present. Measure the size of the gel, and transfer it to a container for incubation with transfer buffer for 15 mm. This incubation is to equilibrate the gel in the new buffer and to reduce the level of SDS, since this reduces the binding of protein to the membrane Gels >l-mm thick will require a 30-min incubation in transfer buffer for this equilibration to take place... 

In tangential filtration, membranes are used as filter media. Membranes are defined as barriers of reduced thickness, across which physical and/or chemical gradients are established to facilitate the preferential migration of one or more components from a given mixture, promoting their separation (Klein, 1991). They are usually made of polymers or inorganic materials, such as ceramic or sintered steel. In the biopharmaceutical industry, membranes find various applications, such as production of water for injection (WFI), sterilization of culture media, buffer solutions and gases, separation of cells and cell debris, and purification and concentration of proteins. 

Figure 1. Transmission spectra of a pAAm/GO/PR membrane (25 mg/mL, 0.307 mm-thick) at four different pH values ( a) and four different glucose concentrations ( b). The spectra were obtained in flowing CBS buffer (0.4 mL/min). Figure la pH 7.4 (—), pH 7.15...

Figure 2. Effect of glucose oxidase concentration on the steady state pH in 0.129 mm-thick pAAm/GO/PR membranes in response to glucose concentration in flowing CBS buffer (2.0 mL/min). Glucose oxidase concentrations (mg/mL) were A 0.05 0.125 0 1.0 ...

Figure 4. Light transmission through a 0.307 mm-thick pAAm/GO/PR membrane with internal Dacron mesh and 25 mg/mL glucose oxidase, as a function of time for changes in glucose concentration from 0-10 mg% (lower curve) and 10-20 mg% (upper curve). Flowrate of buffer was 2.0 mL/min.

In order to prepare liposomes, the lipid preparation is dried at low temperature under an inert gas atmosphere (protect the lipid from oxidation). The lipid film is swollen with water or buffered aqueous solution and several freeze-thaw cycles are carried out to get optimal rehydration of the lipid. The rehydrated lipid preparation is filtered using membrane filters with defined pore size. After repeated filtration steps (extrusion) an unilamellar liposome preparation with a defined size distribution is obtained. Large unilamellar vesicles (LUV) are produced in this way. LUV s are about 100 nm in size the thickness of the lipid bilayer is about 4 nm. Even smaller liposomes can be derived from sonication (sonication probe or ultra-sonication bath). Separation of the prepared liposomes... 

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