Membrane transport case study

In an early study, the author s group synthesised the lipophilic, tri-branched ligand 15 for use in two-phase solvent extraction as well as three phase membrane transport studies [33] the parent ring system in this case has been well documented to interact with a range of first-row transition and post transition ions [34],... 

One in vitro study on rat renal tissue homogenate showed barium weakly inhibited the sodium-potassium-adenosine triphosphatase enzyme system (Kramer et al. 1986). A second study on mouse kidney tubules showed barium chloride could depolarize the membrane and inhibit potassium transport (Volkl et al. 1987). A similar defect in cell membrane transport in humans could be responsible for the renal involvement observed in some cases of acute barium poisoning. 

The aquaporins are a family of small, integral membrane proteins that function as plasma membrane transporters of water and in some cases small polar solutes. There are at least 10 distinct aquaporins in mammals with specific expression patterns in epithelial, endothelial, and other tissues. Studies in aquaporin-null mice indicated a key role for aquaporins in the urinary concentrating mechanism, fluid secretion of glands, brain swelling, skin moisture, hearing and vision, and gastrointestinal absorption.62... 

A new type of configuration, the flowing liquid membrane (FLM) was studied by Teramoto et al. [20]. In this case, the membrane liquid phase is in motion as the feed and strip phase. In this type of system a plate-and-frame and spiral-wound configuration with flat membrane was used. The scheme of the FLM configuration is drawn in Fig. 7.3A. The hquid phase flows (FLM) between two hydrophobic microporous membranes. The two membranes separate the hquid membrane phase from feed and strip phases. In Fig. 7.3B, it is reported the classical plate-and-frame module employed for the separation of ethylene from ethane [20]. The liquid membrane convection increased the membrane transport coefficient in gas separation. However, the membrane surface packing density (membrane surface area/ equipment volume) is much lower in spiral-wound system than in hollow fiber. 

Tbe extraction of phenol has been used by Schlosser and Kossaczky11 and Halwachs et al.16 as a model for studying liquid-membrane transport. The former group compared the liquid-membrane method to a conventional liquid-liquid double extraction process. They concluded thet liquid membranes have disliact economic ndvsmages in cases where type I or type 2 facilitation methods can be used (e.g., phanel or metal ion extractions). However, where one must rely on simple differential permeation (bydrocarbon seperations) rhe ndvantage is less clear-cut. 

As the primary mechanism of action of the. -triazines involves inhibition of PS II electron transport, attention was also directed at analysis of chloroplast reactions in resistant weed biotypes (10, 11, 12). These studies can be summarized as follows (a) in aTl cases studied to date, there is a modification in the chloroplast membranes of resistant biotypes that changes the characteristics of s-triazine binding (b) this modification results in altered bincfTng characteristics of other classes of herbicides, (i.e., only slight resistance to ureas, but increased sensitivity to phenols) (see for review), and (c) the alteration of the herbicide receptor in resistant weeds is accompanied... 

Also, the diffusion boundary layer resistances on either side of the membrane filter in membrane transport processes have been extensively examined [125,126], Most of these studies deal with cases wherein solute diffuses across a membrane filter separating two aqueous phases with different concentrations. However, the individual film mass transfer coefficients in both liquid phases are unavailable. 

Cheetham PSJ (1994) Case studies in applied biocatalysis-from ideas to products. In Cabral IMS, Boros DBL, Tramper J (eds). Applied biocatalysis. Harwood Acad Publ, Chur, pp 47-108 Chen DH, Leu JC, Huang TC (1994) Transport and hydrolysis of urea in a reactor-separator combining an anion-exchange membrane and immobilized urease. J Chem Technol Biotechnol 61(4) 351-357... 

Combinations of these mechanisms may be observed in any membrane system that has distinct fluid, amorphous, crystaUine, and functionalized regions, whether classified as porous or nonporous. Membranes maybe characterized with respect to these mechanistic events, as modeled, based on experimental transport measurements. The analysis tools used to interpret these results are briefly discussed later in the context of this example case study. 

Two limiting situations can be distinguished based on the presence of complex at the receiving side of the membrane. In the case that [LS] ,r is zero, the situation of initial transport is studied and Equation 9 reduces to the so-called "initial flux equation" Jo=(Dm/dm)[LS]nis. In practice, this assumption is valid when the measured flux remains constant with time. Using this assumption, many transport studies have been carried out in which the flux is related to the initial salt concentration in the aqueous source phase, and The initial flux model for the transport of ion-pairs is described in the next section. The initial flux model for assisted transport of free-ions is described in the section after that. 

Experimental studies of the membrane transport by confocal Raman microspectrometry can be carried out only in some specific cases. Amongst various... 

Previously the possibility of using Sc, Sm, and Nd mono- and diphosphorylated amines 1-3 as membrane carriers in conditions of active transport with use of 1,2-dichlorobenzene as a membrane solvent has been shown. At the same time, a high rate of transmembrane transfer of ions Sc and Nd N,N-bis(dihexyl phosphoryl methyl) octyl amine (1) was set. In this paper, the new results of research of membrane transport properties of 1-3 carriers, by symport mechanism are described, and in this case the environmentally acceptable solvent—kerosene as a membrane phase was used. Besides that the membrane-transport properties of diphosphorilamine 4, that have not been described previously containing simultaneously highly lipophilic methyl dioctyl phosphorylic and practically hydrophilic 0,0-diethyl ethyl phosphonate groups in a molecule was studied. It is well-known that creation of optimal hydrophilic-lipophilic balance is a precondition of transmembrane transport effectiveness with organophosphorous carriers. ... 

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