Molecular weight cutoff values

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... 

To purify anserine and carnosine contained in the chicken extract, impurities (mainly creatinine and sodium chloride) need to be removed. Molecular weights of these impurities are 113 and 58, respectively, while average molecular weight of anserine and carnosine is 234. Therefore, 13 different kinds of nanofiltration membranes that had NaCl rejection values of 10% to 60% or molecular weight cutoff values of 700 to 2,500 were chosen. Membranes tested in this study are listed in Table 22.1. 

Bowen and Doneva measured the mean pore dicimeters of five Desal G-series thin film membranes (Osmonics, Vista, USA) with molecular weight cutoff values of 1000 2500 3500 8000 and 10 000 [38]. The MWCO values of these membranes were determined by the manufacturer from the data obtained by UF experiments that were carried out using 1.0 gL polyethylene glycol (PEG) solutions at an operating pressure of 827 kPa and at 25 °C. Pore sizes of these membranes were also calculated... 

Other separators and membranes. The observation that cations or anions can help to maintain charge in an MFC opens the door to new possibilities for using different types of membranes in MFCs. The main function of the membrane is to keep solutions isolated while allowing charge transfer, presumably via small ions. Thus, ultrafiltration (UF) membranes—especially those developed for wastewater applications—may be suitable for use in MFCs. These membranes have tiny pores, with many membranes available that have molecular weight cutoff values below 1000 daltons (IK). UF membranes have appreciable flow through them only under high pressure, and thus under relatively low... 

Boucher-Sharma were made of PEI material and the molecular weight cutoff values of her substrate membranes are relatively large. 

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. 

A crucial characteristic of a membrane is the molecular weight cutoff (MWCO) value, which is defined as the molecular weight at which 90% of the solutes are retained by the membrane. The retention factor R of solute A to be separated by the membrane is defined by the ratio of the concentration of A in the permeate to that in the retentate, as expressed in the following equation ... 

It is noteworthy that these two criteria worked well independently of molecular weight, a property that has been perceived as very important consider a 500Da cutoff that is commonly used to define the drug-Uke molecular weight range. The perception that this property is important probably arises from the apparent dependence of oral bioavailability on properties that correlate with molecular weight, which certainly include the number of rotatable bonds and PSA or H-bond donor count. As such, the value of a hard molecular weight cutoff may need to be reexamined. 

Microfiltration membranes are characterized by bubble point and pore size distribution whereas the UF membranes are typically described by their molecular weight cutoff (MWCO) value. The bubble point pressure relates to the largest pore opening in the membrane layer. This is measured with the help of a bubble point apparatus.t Jt l The average pore diameter of a MF membrane is determined by measuring the pressure at which a steady stream of bubbles is observed. For MF membranes, bubble point pressures vary depending on the pore diameter and nature of membrane material (e.g., hydrophobic or hydrophilic). For example, bubble point values for 0.1 to 0.8 pm pore diameter membranes are reported to vary from 1 bar (equals about... 

Membrane Pore Diameter or Molecular Weight Cutoff. The value of membrane pore diameter will have a major influence on the permeation and separation characteristics for most process filtration applications. The intrinsic membrane permeability is related to the pore diameter for many microfiltration membranes whereas, for ultrafiltration membranes, it is typically indicative of the solute retention properties. Tables 8 and 9 provide typical permeability and retention data for many common MF and UF membranes, respectively.f t ... 

Molecular weight cutoff It refers to be smallest molecular weight of a macrosolute for which the membrane shows at least 90% rejection. This value is typically determined imder a set of well-defined conditions using model compounds (e.g., polyethylene glycols, dextrans and proteins such as BSA) at low concentration. 

Normally, the immobilization of heparinase to agarose catalyst particles is terminated after 4-5 h because greater than 85% of the initial heparinase is bound (49). Based on a cyanate ester stability study, the cyanate ester concentration drops to only 88% of its initial value. For modeling purposes, the cyanate ester concentration was assumed constant. In addition, because of its small size relative to the large molecular weight cutoff (1.5 x 106 daltons) of the catalyst particle, cyanogen bromide (MW 106) should diffuse rapidly into the particle and uniformly activate the matrix. 

Zhang et al. prepared TFC membranes for nanofiltration by interfacial polymerization of piperazine and trimesoyl chloride on top of polysulfone UF membranes with molecular weight cutoff (MWCO) values of 60 000 Da and water permeabilities of 100-150 Lm h bar [28]. Figure 4.12 shows the SEM picture of the sur-... 

In a few cases it has been demonstrated that there is a solute molecular weight cutoff or size (MWC) above which a solute will not diffiise into a solid. Therefore, bottlenecks in cell walls may control the rate of diffusion in solids. Solute molecules that camrot pass through these bottlenecks cannot enter or leave the solid (excepting those portions in which the cell walls are raptured). This suggests that if MWC is known, D, for a solute i can be estimated from die D, for a reference solute r and corresponding known values of Dt, and MW that is. 

Electrolytes are typically prepared from MEEP having molecular weights greater than 5 x 10", a value determined by the molecular weight cutoff property of the dialysis membranes used in the purification of the crude polymer product obtained from the synthesis described by equation [3.4]. 

One of the simplest and most common ways to evaluate a molecule for ADME properties is a qualitative examination of its basic descriptor values such as molecular weight (MW), ClogP for lipophilicity, polar surface area (PSA), counts of hydrogen bond donors and acceptors (HBD, HBA), and count of rotatable bonds (RB). This type of approach popularized by Lipinski s famous Rule of 5 was published a decade ago [6]. Lipinski et al. established cutoffs for MW (500), ClogP (5), HBA (10), and HBD (5). These cutoffs were based on the 90th percentile of distributions of molecules in the World Drug Index having USAN or INN names. The Rule of 5 considers a violation of any two of these cutoffs to be an alert for poor absorption or permeability. 

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