Membranes sequential solutions

Following the recommendations of Buffle, et al. (73), solutions of 150 mg/liter HA, pH 7.0 (TES), 0.10 M NaC104 were ultrafiltered through the membranes sequentially, starting with the largest MWCO. The concentrated fraction of HA retained above the membrane was rinsed twice with a solution of TES buffer,... 

Diafiltration is a variation of ultrafiltration, in which fresh solvent is added to the feed solution to replenish the volume ultrafiltered, and in the process washes small molecules such as salts away from the retained macromolecules. Using appropriate replenishing solutions, diafiltration is a common procedure to perform buffer exchange of proteins. Alternatively, a dilute solution may be first ultrafiltered to concentrate the feed material, then diafiltered to purify the retentate. It is sometimes possible to fractionate a mixture of macrosolutes by sequential diafiltration with a series of membranes of progressively lower molecular weight cutoff ratings. 

Figure 3-14. Hypothetical structures indicating possible mechanisms for transporters and channels in cell membrane (shaded region) (a) mobile carrier or porter acting as a symporter for protons (H+) and some tr ansported solute (5) (b) series of binding sites in a channel across a membrane, acting as a symporter for H+ and S (c) sequential conformations of a channel, leading to unidirectional movement of solute and (d) a protein-lined pore with multiple solute or water molecules hr single file, the most accepted version of ion or water (aquaporirr) channels.

EL-4 cells (3 x 10 ) were lysed with N,N-dimethyl-N-(3-sulfopropyl)-3-[[(3a,5 P,7a, 12a)-3,7,12-trihydroxy-24-oxocholan-24-y 1]-amino]-l-propanaminium hydroxide (CHAPS). The nuclei and membranes were pelleted and the supematent lysate filtered to remove lipids. The lysate was sequentially passed over sepharose columns containing a) normal mouse serum b) Y-3 which is an anti-K monoclonal antibody. Both columns were washed with 45 coliunn volumes of progressively lower molarity salt solutions. The beads were then treated with acetic acid to release antigen-antibody complexes and the complex was denatured by boiling in 10% acetic acid. The mixture was filtered through a 3 kDa pore-size membrane and the filtrate containing MHC class I peptides subjected to reversed phase HPLC. 

In the hot pressing technique, the membrane is often pretreated prior to use. The exact pretreatment depends upon the membrane used, but the pretreatment of Nation 112 is used as an example here. The pretreatment of Nation 112 often consists of a four-step sequential boiling process. The treatment was as follows 3% H2O2, deionized water, 0.5 M H2SO4, and final deionized water. The membrane was placed in each boiling solution for 1 The membrane can... 

Table III illustrated this phenomenon, wherein a single test specimen (made with the piperazine trimesamide homopolymer) was sequentially exposed to feed solutions of sodium chloride, magnesium chloride, sodium sulfate and magnesium sulfate. The chloride salts were both poorly retained while retention of the sulfate salts was excellent. Thus, salt retention in the carboxylate-rich NS-300 membrane was controlled by the anion size and charge. This membrane could not distinguish between the univalent sodium ion and the divalent magnesium ion, which is the opposite of the behavior observed for asymmetric cellulose acetate membranes. Salt passage through the NS-300 membrane may be described as anion-controlled.

Fig. 2 The construction of a polymer-cushioned lipid bilayer membrane. (A) Architecture constructed in a sequential way first, onto the functionalized substrate a polymer layer (cushion) is deposited by adsorption from solution and covalent binding, followed by the (partial) covalent attachment of a lipid monolayer containing some anchor lipids as reactive elements (B) able to couple the whole monolayer to the polymer cushion. (C) Alternatively, a lipopolymer monolayer, organized, e.g., at the water-air interface can be co-spread with regular low-mass amphiphiles and then transferred as a mixed monolayer onto a solid support, prefunctionalized with reactive groups, able to bind covalently to the polymer chains of the lipopolymer molecules, (B). (D) By a fusion step (or a Langmuir Schaefer transfer) the distal lipid monolayer completes the polymer-tethered membrane architecture...

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