Home About us Contact
|
Home About us Contact | ||
|
|
||
Organic Solvent Mixture (organic + solvent_mixture)
Selected AbstractsNMR investigations of subunit c of the ATP synthase from Propionigenium modestum in chloroform/methanol/water (4 : 4 : 1)FEBS JOURNAL, Issue 7 2002Ulrich Matthey The subunit c from the ATP synthase of Propionigenium modestum was studied by NMR in chloroform/methanol/water (4 : 4 : 1). In this solvent, subunit c consists of two helical segments, comprised of residues L5 to I26 and G29 to N82, respectively. On comparing the secondary structure of subunit c from P. modestum in the organic solvent mixture with that in dodecylsulfate micelles several deviations became apparent: in the organic solvent, the interruption of the ,,helical structure within the conserved GXGXGXGX motif was shortened from five to two residues, the prominent interruption of the ,,helical structure in the cystoplasmic loop region was not apparent, and neither was there a break in the ,,helix after the sodium ion-binding Glu65 residue. The folding of subunit c of P. modestum in the organic solvent also deviated from that of Escherichia coli in the same environment, the most important difference being that subunit c of P. modestum did not adopt a stable hairpin structure like subunit c of E. coli. [source] Determination of phenol using an enhanced chemiluminescent assayLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 1 2003A. D. Ilyina Abstract Enhanced chemiluminescence (ECL) describes the phenomenon of increased light output in the luminol oxidation reaction catalysed by horseradish peroxidase (HRP) in the presence of certain compounds, such as para -iodophenol. In this work, the effects of phenol on the para -iodophenol-enhanced HRP-catalysed chemiluninescent reaction intensity in an aqueous buffer (Tris,HCl buffer, pH 8.5) and in a surfactant,water,octane mixture were compared. Preincubation of HRP at low phenol concentrations stimulated the chemiluminescent intensity in the assay performed in an aqueous buffer, but did not have significant effect in the sodium bis(2-ethylhexyl)sulphosuccinate) (Aerosol OT, AOT) applied system. It was also observed that HRP preincubation with phenol concentration higher than 0.003,mg/mL produced an inhibitory effect on the enzyme activity for both assay systems. Only an inhibitory effect of phenol on the chemiluminescent intensity in the surfactant system in octane (as organic solvent) was observed. Three assays were developed to determine phenol concentration in water and in an organic solvent mixture. The detection limits were 0.006, 0.003 and 0.0005,mg/mL, respectively, for the buffer-containing system, the AOT-applied system with phenol standard solutions in water and for the AOT-applied system with phenol standard solutions in octane. Copyright © 2002 John Wiley & Sons, Ltd. [source] Synthesis of well-defined photoresist materials by SET-LRPJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2010Sven Fleischmann Abstract Single electron transfer-living radical polymerization (SET-LRP) provides an excellent tool for the straightforward synthesis of well-defined macromolecules. Heterogeneous Cu(0)- catalysis is employed to synthesize a novel photoresist material with high control over the molecular architecture. Poly(,-butyrolactone methacrylate)- co -(methyladamantly methacrylate) was synthesized. Kinetic experiments were conducted demonstrating that both monomers, ,-butyrolactone methacrylate (GBLMA) and methyl adamantly methacrylate (MAMA), are successfully homopolymerized. In both cases polymerization kinetic is of first order and the molecular weights increase linearly with conversion. The choice of a proper solvent was decisive for the SET-LRP process and organic solvent mixtures were found to be most suitable. Also, the kinetic of the copolymerization of GBLMA and MAMA was investigated. Following first order kinetics in overall monomer consumption and exhibiting a linear relationship between molecular weights and conversion a "living" process was established. This allowed for the straightforward synthesis of well-defined photoresist polymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2251,2255, 2010 [source] Structural motifs in the maturation process of peptide hormones.JOURNAL OF PEPTIDE SCIENCE, Issue 2 2002The somatostatin precursor. Abstract Synthetic peptides reproducing both the native domain around the dibasic cleavage site of pro-somatostatin, and mutated sequences thereof, previously assayed in site-directed mutagenesis experiments, have been studied by CD in different solvent systems, such as water, TFE/H2O, MeCN/H2O and aqueous SDS, in order to ascertain the ability of each solvent to stabilize secondary structural motifs. A combination of deconvolution methods and empirical calculations, that allow subtraction of the contributions due to unordered structures from the spectra, suggests that mainly two distinct families of ordered conformers containing ,-helix and/or structurally different ,-turns are present in solution, the relative stability of the different conformers depending on the nature of the solvent. The presence of ,-turns is in line with a previous NMR study in DMSO and DMSO/H2O. Comparison of the CD spectra in aqueous SDS of peptides undergoing processing with a sequence not processed in vivo shows that only the latter possesses a stable and detectable ,-helix population. This observation suggests that the structuration involving ,-turns but no ,-helix, which was observed by CD both in SDS and organic solvent/H2O mixtures at high water contents, might be of biological significance. The similarity of this structuration to molecular models obtained from NMR data in DMSO and DMSO/H2O is discussed. Copyright © 2002 European Peptide Society and John Wiley & Sons, Ltd. [source] | ||||||||||