Stability of Ion Exchange Membranes in Electrodialysis.

During electrodialysis the ion exchange membranes are affected by such factors as passage of electric current, heating, tangential flow of solution and exposure to chemical agents. It can potentially cause the degradation of ion exchange groups and of polymeric backbone, worsening the performance of the process and necessitating the replacement of the membranes. This article aims to review how the composition and the structure of ion exchange membranes change during the electrodialysis or the studies imitating it.

Short-Term Stability of Electrochemical Properties of Layer-by-Layer Coated Heterogeneous Ion Exchange Membranes.

Layer-by-layer adsorption allows the creation of versatile functional coatings for ion exchange membranes, but the stability of the coating and resulting properties of modified membranes in their operation is a frequently asked question. This paper examines the changes in voltammetric curves of layer-by-layer coated cation exchange membranes and pH-metry of desalination chamber with a studied membrane and an auxiliary anion exchange membrane after short-term tests, including over-limiting current modes. The practical operation of the membranes did not affect the voltammetric curves, but enhanced the generation of H and OH ions in a system with polyethylenimine modified membrane in Ca containing solution.

Cation binding site of cytochrome c oxidase: progress report.

Cytochrome c oxidase from bovine heart binds Ca(2+) reversibly at a specific Cation Binding Site located near the outer face of the mitochondrial membrane. Ca(2+) shifts the absorption spectrum of heme a, which allowed earlier the determination of the kinetic and equilibrium characteristics of the binding, and, as shown recently, the binding of calcium to the site inhibits cytochrome oxidase activity at low turnover rates of the enzyme [Vygodina, Т., Kirichenko, A.

Direct regulation of cytochrome c oxidase by calcium ions.

Cytochrome c oxidase from bovine heart binds Ca(2+) reversibly at a specific Cation Binding Site located near the outer face of the mitochondrial membrane. Ca(2+) shifts the absorption spectrum of heme a, which allowed previously to determine the kinetics and equilibrium characteristics of the binding. However, no effect of Ca(2+) on the functional characteristics of cytochrome oxidase was revealed earlier.

Inhibition of lactophage activity by quinolinilporphyrin and its zinc compex.

The influence of free base of quinolinilporphyrin and its Zn complex on infectivity of lactophages E3, E5 and E17 has been studied. The results of our investigations show that inhibition of lactophage activity by Zn complex of quinolinilporphyrin at concentration 10 microM and 20 microM was in the range 53-62% and 65-85%, respectively. The presence of this porphyrin in nutrient medium prevents the propagation of bacteriophage infection in Lactococcus lactis, but does not affect the phage adsorption process.

Cytochrome c oxidase as a calcium binding protein. Studies on the role of a conserved aspartate in helices XI-XII cytoplasmic loop in cation binding.

The aa(3)-type cytochrome c oxidases from mitochondria and bacteria contain a cation-binding site located in subunit I near heme a. In the oxidases from Paracoccus denitrificans or Rhodobacter sphaeroides, the site is occupied by tightly bound calcium, whereas the mitochondrial oxidase binds reversibly calcium or sodium that compete with each other. The functional role of the site has not yet been established.

Ca(2+)-binding site in Rhodobacter sphaeroides cytochrome C oxidase.

Cytochrome c oxidase (COX) from R. sphaeroides contains one Ca(2+) ion per enzyme that is not removed by dialysis versus EGTA. This is similar to COX from Paracoccus denitrificans [Pfitzner, U.