Membrane coupling

Energy-linked transhydrogenase, a protein in the inner mitochondrial membrane, couples the passage of protons down the electrochemical gradient from outside to inside the mitochondrion with the transfer of H from intramitochondrial NADH to NADPH for intramitochondrial enzymes such as glutamate dehydrogenase and hydroxylases involved in steroid synthesis. 

Fig.3. Mechanism of PET across a lipid membrane, coupled with H2 evolution in EDTA-Ru(bipy) j -V -Pd / lipid vesicle system.

Zdzislaw, S. Gordon, T., Optical anisotropy in lipid bilayer membranes Coupled plasmon waveguide resonance measurements of molecular orientation, polarizability, and shape, Biophys. J. 2001, 80, 1557 1567... 

Naringenin, other flavones, and the cinnamic acids could behave like quercetin. Hence, at least some of the phenolic allelochemlcals could prevent the utilization of ATP energy required for transport of materials across cellular membranes by inhibiting the hydrolysis of ATP. Conceivably, alterations induced to the permeability of organelle membranes coupled... 

Step 3 at the SLM-stripping interface, QP releases P ions into the aqueous phase, CL ions replace P ions in the membrane (coupled transport). 

I am disturbed that following Professor Hammes presentation the language in the discussion has changed. While discussing enzymes we looked at molecule properties closely related to the discussion of small molecules (e.g., atom position and motions). Now in the discussion of complex enzymes, especially in membranes, we have started to use bulk properties (e.g., we talk of phases, dielectric constants, Chapman-Gouy theory, etc.). Is it the view of the discussants that events in membrane-coupled-enzyme systems cannot be described by molecular events because of the complexity of the system resulting from extensive cooperativ-ity within the membrane (e.g., between lipids and proteins) ... 

Membranes coupling endo- and exothermic reaction zones (e.g., hydrogenation-dehydrogenation) Supported liquid membranes (SLM) for homogeneous catalytic processes... 

Xing, C.-H., Wena, X.-H. and Tardieub, E. (2001) Microfiltration-membrane-coupled bioreactor for urban wastewater reclamation. Desalination, 141, 63-73. 

Alternatively to diffusion dialysis, Pierard et al. [96] suggested electrodialysis as a regeneration process. In the case study involving acid pickling before electroplating, they demonstrated the selection of ion-exchange membrane couples as well as the development of tools to promote the use of electrodialysis in industrial applications. 

As imphed by equation (3), and by the location of the O2 reduction site in the structure, proton transfer across the cytochrome oxidase protein is required for function, which necessitates proton-conducting pathways for three specific purposes, that is, to transfer the four substrate protons from the A-side of the membrane into the site of O2 reduction, for uptake of the four pumped protons (per O2 reduced) that are translocated across the membrane coupled to the redox reaction, and for release of these protons to the opposite side of the membrane (exit pathway). Site-directed mutagenesis data indicated the presence of two proton transfer pathways from the A-side of the membrane toward the binuclear heme... 

A holy grail for DON (and DOM in general) remains a rapid and portable method to quantitatively isolate and desalt a large dissolved sample (Bronk, 2002). Such a method would not only allow a wealth of diverse techniques to be brought to bear on the largest unknown fraction of DON, but would allow direct isotopic measurements and compound-specific mass balances. Examples of some approaches currently being explored to improve DON recovery on both small and large scales include homemade ion-retardation resins (Bronk, unpublished data), electrodialysis (Vetter et al, 2007), and use of nano-filtration membranes coupled to standard ultrafiltration approaches (McCarthy et al unpubhshed data). 

According to the third catalyst-membrane coupling possibility, represented in Fig. 5c, the surface of the membrane is deposited with some catalytic material. This setup is typical of solid-electrolyte membranes, where the catalyst is also playing the role of the electrode, necessary to drive the permeation of ions throughout the membrane at a desired rate. Problems may arise here concerning the fact that the catalyst per unit membrane surface is limited to some extent, and that several catalytic materials (e.g., metal oxides) are poor electricity conductors [26]. 

Djane N-K, Armalis S, Ndung u K, Johansson G, and Mathiasson L. Supported liquid membrane coupled on-line to potentiometric stripping analysis at a mercury-coated reticulated vitreous carbon electrode for trace metal determinations in urine. Analyst 1998 123 393-396. 

Klatt CG and LaPara TM. Aerobic biological treatment of synthetic municipal wastewater in membrane-coupled bioreactors. Biotechnol Bioeng. 2003 82 313-320. 

In spite of the clear advantages, membrane-coupled processes often turn out to be still more expensive, because of the costs of membrane and all additional hardware associated with a membrane operation. Membrane separations tend to become more favorable for processes where the selectivity is more important than the conversion, because it replaces other purification steps that might lower such selectivities, like in the production of the chiral diltiazem intermediate. Membrane fouling, mass transfer limitations, biocatalyst activity loss, and biocatalyst denaturation are other potential disadvantages related to it. 

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