Molecular weight cutoff

Molecular Weight Cutoff The best-known method for characterizing UF membranes is molecular weight cutoff. Unfortunately, it is widely misunderstood and has been the source of much error. The concept of molecular weight cutoff (MWCO) is powerful and deceptively simple. Ultrafilters retain soluble molecules, so their retention is... 

Macroporous polyvinyl alcohol particles with a molecular weight cutoff of ca. 8 X 10 in gel-permeation chromatography have been prepared. The particles are produced by first dispersing an aqueous solution of polyvinyl alcohol in an organic solvent to make spheres of polyvinyl alcohol solution. Holding the dispersion in such a state that a gel will then form spontaneously will cause the gel to react with glutaraldehyde in the presence of an acidic catalyst (85). 

The polyethersulfone capillary ultrafiltration membranes (Daicel Chemical Industries, Ltd., inner diameter 0.8 mm, outer diameter 1.3 mm, length 40 cm, molecular weight cutoff 150 000, water permeability 3 x 10 m m s kPa at 298 K) were used. The length and area of membrane consisting of seven hollow fibers are 40 cm and 70 cm. ... 

A bench top polysulfone hollow fiber membrane (0.0325m ) with molecular weight cutoff (MWCO) of 30K (A/G Technology Corp., Needham MA) was used (24). UF was run in a total recycle mode at a rate of 1.2 L/min (flow speed of 0.73 m/sec), cross membrane pressure of 25 PSIG and 10 + 1°C. PE permeability is expressed as the fraction of PEU/mL in the permeate to PEU/mL in the retentate. Data presented are representative of at least duplicate replications. 

Ethyl laurate-water Molecular weight cutoff = 500Da, Product name BM5, Berghof 116... 

Materials. Deionized-distilled water was used for all syntheses and distilled water was used in all solutions. All salts were reagent grade and were used as received. Dialysis membrane was Spectrapor no. 2, 12,000 upper molecular-weight-cutoff membrane from Spectrum Medical Industries, Los Angeles, CA. 

Dialyze eluted proteins twice in 1 liter Dialysis Buffer using Slide-A-Lyzer dialysis cassettes (Pierce) with a 30,000 molecular weight cutoff (MWTco). Because the eIF2Becat domain is 25.9 KDa, dialysis of small domains requires a lower MWTco membrane. Therefore, 15,000 MWTco Float-A-Lyzer dialysis membranes (Spectrum) are used. 

After cooling to room temperature, the sugar-dendrimer derivative may be precipitated with a large volume of methanol. The precipitate may be purified from reaction products by dialysis against water or buffer using a membrane with a molecular weight cutoff of 3500 Daltons. The final product may be stored frozen or lyophilized to a white powder. 

Remove unreacted dye and reaction by-products from the modified dendrimer by gel filtration or dialysis, using a molecular weight cutoff suitable for the size of the dendrimer. 

Purify the DTPA-dendrimer using dialysis, size exclusion chromatography, or spin-tube concentrators having a molecular weight cutoff of 5,000 Daltons. 

To recover a protein that has been completely reduced and labeled, precipitate the protein by the addition of 9 volumes of methanol at — 20°C. Collect the protein pellet by centrifugation at 8,000g for 15 minutes (4°C). If partial reduction was done followed by labeling with 5-IAF, then purify the labeled protein by gel filtration or dialysis using a molecular weight cutoff of about 5,000 D. 

Purify the modified protein from reaction by-products by dialysis using a membrane with a low molecular weight cutoff or gel filtration using desalting resin and a buffer consisting of 50mM sodium phosphate, 0.15M NaCl, lOmM EDTA, pH 7.2. 

Purify the modified oligo from unreacted crosslinker and reaction byproducts using a micro-spin concentrator with a membrane having a molecular weight cutoff able to retain the size of the DNA being modified. 

Purify the modified protein by gel filtration or dialysis using a molecular weight cutoff that will be appropriate for the protein being modified. 

Molecular weight cutoff, 15 829 Molecular weight determination, for polysaccharides, 20 551 Molecular weight distribution (MWD), 20 530-531... 

The retention properties of ultrafiltration membranes are expressed as Molecular Weight Cutoff (MWCO). This value refers to the approximate molecular weight (MW) of a dilute globular solute (i.e., a typical protein) which is 90% retained by the membrane. However, a molecule s shape can have a direct effect on its retention by a membrane. For example, linear molecules like DNA may find their way through pores that will retain a globular species of the same molecular weight. 

Figure 1. Production of Fe(II) on irradiation of pH 4.0 solutions of distilled, deionized water and 0.1M NaCl and a pH 6.5 solution of 0.1M NaCl/2mM NaHC03 containing 3.5pM am-FeOOH. The ultrafilterability of the iron through a membrane exhibiting a nominal molecular weight cutoff of 10,000 (Amicon PM10) in the pH 4.0 study is also shown. Light source simulated solar spectrum of total intensity 300 pEinsteins cm-2 min-1. (Reproduced from Ref. 32. Copyright 1984, American Chemical Society.)...

In addition to molecular weight, percentage saturation of the standard Daylight fingerprint has been used to describe the degree of molecular functionality [78]. Compounds with saturation outside a certain range (e.g., <10% and >60% saturation) can be excluded in order to remove overly simple or complicated molecules that would otherwise pass a simple molecular weight cutoff. 

In a dialysis procedure, enzyme should be preincubated with a concentration of inhibitor sufficient to reduce activity by at least 90%. A solution containing the inhibited enzyme is then placed inside a small bag fashioned from dialysis membrane with a molecular weight cutoff value substantially lower than the mass of the enzyme. The sealed dialysis bag is then placed in a beaker containing a large volume of buffer, and is left... 

The dialysis chambers are assembled. We use microdialysis chambers in which the volume of the two compartments is 0.35-0.4 ml. The chambers are separated by 50,000 molecular weight cutoff SpectraPor dialysis tubing. 

---