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Micellar Environment (micellar + environment)
Selected AbstractsLignin Chemistry: Biosynthetic Study and Structural Characterisation of Coniferyl Alcohol Oligomers Formed In Vitro in a Micellar EnvironmentCHEMISTRY - A EUROPEAN JOURNAL, Issue 20 2010Samantha Reale Dr. Abstract Model coniferyl alcohol lignin (the so-called dehydrogenative polymerisate, DHP) was produced in water under homogeneous conditions guaranteed by the presence of a micellised cationic surfactant. A complete study of the activity of the enzymatic system peroxidase/H2O2 under our reaction conditions was reported and all the reaction products up to the pentamer were characterised by 1H,NMR spectroscopy and ESI mass spectrometry. Our system, and the molecules that have been generated in it, represent a closer mimicry of the natural microenvironment since an enzyme, under micellar conditions, reproduces the cell system better than in buffer alone. On the basis of the oligomers structures a new biosynthetic perspective was proposed that focused attention on a coniferyl alcohol dimeric quinone methide as the key intermediate of the reaction. A formal, strictly alternate sequence of a radical and an ionic step underlines the reaction, thus generating ordered oligolignols structures. Alternatively to other model lignins, our olignols present a lower degree of radical coupling between oligomeric units. This offers a closer biosynthetic situation to the observation of a low rate of radical generation in the cell wall. [source] Functional and structural properties of stannin: Roles in cellular growth, selective toxicity, and mitochondrial responses to injuryJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 2 2006M.L. Billingsley Abstract Stannin (Snn) was discovered using subtractive hybridization methodology designed to find gene products related to selective organotin toxicity and apoptosis. The cDNAs for Snn were first isolated from brain tissues sensitive to trimethyltin, and were subsequently used to localize, characterize, and identify genomic DNA, and other gene products of Snn. Snn is a highly conserved, 88 amino acid protein found primarily in vertebrates. There is a minor divergence in the C-terminal sequence between amphibians and primates, but a nearly complete conservation of the first 60 residues in all vertebrates sequenced to date. Snn is a membrane-bound protein and is localized, in part, to the mitochondria and other vesicular organelles, suggesting that both localization and conservation are significant for the overall function of the protein. The structure of Snn in a micellar environment and its architecture in lipid bilayers have been determined using a combination of solution and solid-state NMR, respectively. Snn structure comprised a single transmembrane domain (residues 10,33), a 28-residue linker region from residues 34,60 that contains a conserved CXC metal binding motif and a putative 14-3-3, binding region, and a cytoplasmic helix (residues 61,79), which is partially embedded into the membrane. Of primary interest is understanding how this highly-conserved peptide with an interesting structure and cellular localization transmits both normal and potentially toxic signals within the cell. Evidence to date suggests that organotins such as trimethyltin interact with the CXC region of Snn, which is vicinal to the putative 14-3-3 binding site. In vitro transfection analyses and microarray experiments have inferred a possible role of Snn in several key signaling systems, including activation of the p38-ERK cascade, p53-dependent pathways, and 14-3-3, protein-mediated processes. TNF, can induce Snn mRNA expression in endothelial cells in a PKC-, dependent manner. Studies with Snn siRNA suggest that this protein may be involved in growth regulation, since inhibition of Snn expression alone leads to reduced endothelial cells growth and induction of COP-1, a negative regulator of p53 function. A key piece of the puzzle, however, is how and why such a highly-conserved protein, localized to mitochondria, interacts with other regulatory proteins to alter growth and apoptosis. By knowing the structure, location, and possible signaling pathways involved, we propose that Snn constitutes an important sensor of mitochondrial damage, and plays a key role in the mediation of cross-talk between mitochondrial and nuclear compartments in specific cell types. J. Cell. Biochem. 98: 243,250, 2006. © 2006 Wiley-Liss, Inc. [source] Oxidation and chemiluminescence of catechol by hydrogen peroxide in the presence of Co(II) ions and CTAB micellesLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 5 2007Jan Lasovsky Abstract The oxidation of catechol in neutral and slightly alkaline aqueous solutions (pH 7,9.6) by excess hydrogen peroxide (0.002,0.09 mol/L) in the presence of Co(II) (2.10,7,2.10,5 mol/L) is accompanied by abrupt formation of red purple colouration, which is subsequently decolourized within 1 h. The electron spectra of the reaction mixture are characterized by a broad band covering the whole visible range (400,700 nm), with maximum at 485 nm. The reaction is initiated by catechol oxidation to its semiquinone radical and further to 1,2-benzoquinone. By nucleophilic addition of hydrogen peroxide into the p -position of benzoquinone C=O groups, hydroperoxide intermediates are formed, which decompose to hydroxylated 1,4-benzoquinones. It was confirmed by MS spectroscopy that monohydroxy-, dihydroxy- and tetrahydroxy-1,4-benzoquinone are formed as intermediate products. As final products of catechol decomposition, muconic acid, its hydroxy- and dihydroxy-derivatives and crotonic acid were identified. In the micellar environment of hexadecyltrimethylammonium bromide the decomposition rate of catechol is three times faster, due to micellar catalysis, and is accompanied by chemiluminescence (CL) emission, with maxima at 500 and 640 nm and a quantum yield of 1 × 10,4. The CL of catechol can be further sensitized by a factor of 8 (maximum) with the aid of intramicellar energy transfer to fluorescein. Copyright © 2007 John Wiley & Sons, Ltd. [source] Amphipathic control of the 310 -/,-helix equilibrium in synthetic peptidesCHEMICAL BIOLOGY & DRUG DESIGN, Issue 2 2001L. G. J. Hammarström Abstract: A series of short, amphipathic peptides incorporating 80% C,,C, -disubstituted glycines has been prepared to investigate amphipathicity as a helix-stabilizing effect. The peptides were designed to adopt 310 - or ,-helices based on amphipathic design of the primary sequence. Characterization by circular dichroism spectroscopy in various media (1,:,1 acetonitrile/water; 9,:,1 acetonitrile/water; 9,:,1 acetonitrile/TFE; 25 mm SDS micelles in water) indicates that the peptides selectively adopt their designed conformation in micellar environments. We speculate that steric effects from ith and ith + 3 residues interactions may destabilize the 310 -helix in peptides containing amino acids with large side-chains, as with 1-aminocyclohexane-1-carboxylic acid (Ac6c). This problem may be overcome by alternating large and small amino acids in the ith and ith + 3 residues, which are staggered in the 310 -helix. [source] | |||||||||||||