Search results for "membrana"
showing 10 items of 91 documents
Recuperación de metano disuelto en el efluente de un reactor anaerobio de lecho expandido mediante contactores de membrana
2017
La emisión de gases de efecto invernadero (GEI) a la atmósfera supone uno de los problemas medioambientales más importantes en la actualidad, debido a su relación con el calentamiento global y el cambio climático. En este sentido, uno de los GEI más relevantes es el metano, con un potencial de calentamiento global 28 veces superior al del dióxido de carbono. El sector del tratamiento de aguas residuales contribuye a las emisiones de metano, siendo de especial relevancia los tratamientos anaerobios que se llevan a cabo a temperatura ambiente. En estos sistemas, una parte del metano generado puede encontrarse disuelto en el efluente del proceso, debido al aumento de la solubilidad del metano …
Electrical Pumping of Potassium Ions Against an External Concentration Gradient in a Biological Ion Channel
2013
We show experimentally and theoretically that significant currents can be obtained with a biological ion channel, the OmpF porin of Escherichia coli, using zero-average potentials as driving forces. The channel rectifying properties can be used to pump potassium ions against an external concentration gradient under asymmetric pH conditions. The results are discussed in terms of the ionic selectivity and rectification ratio of the channel. The physical concepts involved may be applied to separation processes with synthetic nanopores and to bioelectrical phenomena. (C) 2013 AIP Publishing LLC.
PEMANFAATAN HEWAN SEBAGAI OBAT TRADISIONAL DALAM KEHIDUPAN SUKU HATTAM DI KAMPUNG MOKWAM MENYAMBOUW
2008
<p><em>This research aim to document traditional knowledge (indigenous knowledge) of the Hattam tribe in exploiting animals as traditional drug, in which the observation was done on the animal type, way of exploiting, and also on other culture and knowledge related to pattern of exploiting animals as drug in the life of the tribe. The result shows that there are 9 animals used as traditional drug in the life of the Hattam tribe in Mokwam village, that is: Rana grisea, Litoria arfakiana, Litoria micromembrana, Litoria angiana, Nyctimystes pulchra, Accipiter sp., Morelia viridis, Micropechis sp., and Sus sp. The animals were used as drugs to cure skin disease (purities), bloated, …
Peptides corresponding to helices 5 and 6 of Bax can independently form large lipid pores
2006
Proteins of the B-cell lymphoma protein 2 (Bcl2) family are key regulators of the apoptotic cascade, controlling the release of apoptotic factors from the mitochondrial intermembrane space. A helical hairpin found in the core of water-soluble folds of these proteins has been reported to be the pore- forming domain. Here we show that peptides including any of the two a-helix fragments of the hairpin of Bcl2 associated protein X (Bax) can independently induce release of large labelled dextrans from synthetic lipid vesicles. The permeability promoted by these peptides is influenced by intrinsic monolayer curvature and accompanied by fast transbilayer redis- tribution of lipids, supporting a to…
Charge Pair Interactions in Transmembrane Helices and Turn Propensity of the Connecting Sequence Promote Helical Hairpin Insertion
2013
alpha-Helical hairpins, consisting of a pair of closely spaced transmembrane (TM) helices that are connected by a short interfacial turn, are the simplest structural motifs found in multi-spanning membrane proteins. In naturally occurring hairpins, the presence of polar residues is common and predicted to complicate membrane insertion. We postulate that the pre-packing process offsets any energetic cost of allocating polar and charged residues within the hydrophobic environment of biological membranes. Consistent with this idea, we provide here experimental evidence demonstrating that helical hairpin insertion into biological membranes can be driven by electrostatic interactions between clo…
Membrane insertion and topology of the TRanslocating chain-Associating Membrane protein (TRAM)
2011
The translocating chain-associating membrane protein (TRAM) is a glycoprotein involved in the translocation of secreted proteins into the endoplasmic reticulum (ER) lumen and in the insertion of integral membrane proteins into the lipid bilayer. As a major step toward elucidating the structure of the functional ER translocation/insertion machinery, we have characterized the membrane integration mechanism and the transmembrane topology of TRAM using two approaches: photocross-linking and truncated C-terminal reporter tag fusions. Our data indicate that TRAM is recognized by the signal recognition particle and translocon components, and suggest a membrane topology with eight transmembrane seg…
Influence of proline residues in transmembrane helix packing
2003
Integral membrane proteins often contain proline residues in their alpha-helical transmembrane (TM) fragments, which may strongly influence their folding and association. Pro-scanning mutagenesis of the helical domain of glycophorin A (GpA) showed that replacement of the residues located at the center abrogates helix packing while substitution of the residues forming the ending helical turns allows dimer formation. Synthetic TM peptides revealed that a point mutation of one of the residues of the dimerization motif (L75P) located at the N-terminal helical turn of the GpA TM fragment, adopts a secondary structure and oligomeric state similar to the wild-type sequence in detergents. In additi…
BB0172, a Borrelia burgdorferi Outer Membrane Protein That Binds Integrin Α3Β1
2013
ABSTRACT Lyme disease is a multisystemic disorder caused by Borrelia burgdorferi infection. Upon infection, some B. burgdorferi genes are upregulated, including members of the microbial surface components recognizing adhesive matrix molecule (MSCRAMM) protein family, which facilitate B. burgdorferi adherence to extracellular matrix components of the host. Comparative genome analysis has revealed a new family of B. burgdorferi proteins containing the von Willebrand factor A (vWFA) domain. In the present study, we characterized the expression and membrane association of the vWFA domain-containing protein BB0172 by using in vitro transcription/translation systems in the presence of microsomal …
Influence of the C-terminus of the glycophorin A transmembrane fragment on the dimerization process
2000
The monomer-dimer equilibrium of the glycophorin A (GpA) transmembrane (TM) fragment has been used as a model system to investigate the amino acid sequence requirements that permit an appropriate helix-helix packing in a membrane‐mimetic environment. In particular, we have focused on a region of the helix where no crucial residues for packing have been yet reported. Various deletion and replacement mutants in the C‐terminal region of the TM fragment showed that the distance between the dimerization motif and the flanking charged residues from the cytoplasmic side of the protein is important for helix packing. Furthermore, selected GpA mutants have been used to illustrate the rearrangement o…
RNA-binding properties and membrane insertion of Melon necrotic spot virus (MNSV) double gene block movement proteins
2006
AbstractAdvances in structural and biochemical properties of carmovirus movement proteins (MPs) have only been obtained in p7 and p9 from Carnation mottle virus (CarMV). Alignment of carmovirus MPs revealed a low conservation of amino acid identity but interestingly, similarity was elevated in regions associated with the functional secondary structure elements reported for CarMV which were conserved in all studied proteins. Nevertheless, some differential features in relation with CarMV MPs were identified in those from Melon necrotic virus (MNSV) (p7A and p7B). p7A was a soluble non-sequence specific RNA-binding protein, but unlike CarMV p7, its central region alone could not account for t…