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731.
Balchen M Hatterud AG Reubsaet L Pedersen-Bjergaard S 《Journal of separation science》2011,34(2):186-195
By the application of an electrical potential difference (25 V), 37 different peptides were extracted from 500 μL aqueous sample (10 mM formic acid, positive electrode), through a supported liquid membrane (SLM) impregnated in the walls of a porous hollow fiber, and into 25 μL aqueous acceptor solution (100 mM formic acid, negative electrode) present inside the lumen of the fiber. Most of the peptides were obtained by tryptic digestion of cytochrome c and bovine serum albumin, which yielded complex samples for extraction. Three different SLMs were utilized to correlate the peptides extractability with the highly variable physical-chemical properties of the peptides. The first SLM (pure eugenol) provided an electromembrane extraction system for hydrophobic and intermediate peptides (hydrophilicity values below 0.2), where the extraction of peptides into the SLM was mainly based on solvent interactions. The second SLM (1-octanol/di-isobutylketone/di-(2-ethylhexyl) phosphate) extracted both hydrophobic and hydrophilic peptides (hydrophilicity values in the range from -2 to+1) successfully, and the transfer of peptides was principally based on ionic interactions with di-(2-ethylhexyl) phosphate. The third SLM (1-octanol/15-crown-5 ether) was selective for hydrophobic peptides (negative hydrophilicity values), and complexation of the peptides with the crown ether was important for the migration of peptides into the acceptor solution. 相似文献
732.
Seip KF Stigsson J Gjelstad A Balchen M Pedersen-Bjergaard S 《Journal of separation science》2011,34(23):3410-3417
A large screening of different components in the supported liquid membrane (SLM) in electromembrane extraction (EME) was performed to test the extraction efficiency on eight model peptides. Electromembrane extraction from a 500 μL acidified aqueous sample containing the model peptides in the concentration 10 μg/mL was used. Extraction time was 5 min with an electric potential of 10 V and 900 rpm agitation of the sample vial. The samples were extracted through a hollow fiber-based SLM with different compositions of organic solvents and carriers. A small volume of acidified acceptor solution (25 μL) was after extraction analyzed directly, or with some dilution, on CE or HPLC. This article has identified mono- or di-substituted phosphate groups as the prominent group of carrier molecules needed to obtain acceptable recoveries. For the organic solvents, primary alcohols and ketones have shown promise regarding recovery and reproducibility, with some differences in selectivity. A new composition of the SLM, namely 2-octanone and tridecyl phosphate (90:10 w/w) has proved to give higher extraction recoveries and lower standard deviation than SLMs previously reported in the literature. 相似文献
733.
Dieter Seebach 《Helvetica chimica acta》2011,94(1):1-17
Fmoc‐β2hSer(tBu)‐OH was converted to Fmoc‐β2hSec(PMB)‐OH in five steps. To avoid elimination of HSeR, the selenyl group was introduced in the second last step (Fmoc‐β2hSer(Ts)‐OAll→Fmoc‐β2hSec(PMB)‐OAll). In a similar way, the N‐Boc‐protected compound was prepared. With the β2hSe‐derivatives, 21 β2‐amino‐acid building blocks with proteinogenic side chains are now available for peptide synthesis. 相似文献
734.
Michele FioreMauro Lo Conte Salvatore PacificoAlberto Marra Alessandro Dondoni 《Tetrahedron letters》2011,52(3):444-447
We report on the photoinduced addition of glycosyl thiols to alkenyl glycines (thiol-ene coupling) to give S-glycosyl amino acids in high yields (53-90%). One of the amino acids thus prepared was used in the construction of a tripeptide via solution phase chemistry. Moreover, a one-pot two-step approach to an S-glycopeptide was developed using glutathione (GSH) as model starting material. This approach involved GSH S-alkenylation followed by photoinduced hydrothiolation by a glycosyl thiol. 相似文献
735.
Staub A Zurlino D Rudaz S Veuthey JL Guillarme D 《Journal of chromatography. A》2011,1218(49):8903-8914
The objective of this study was to evaluate the potential of sub-2 μm totally porous particles and sub-3 μm shell particles for peptide and protein analysis. Specific analytical strategies must be developed for these biomolecules as their importance in the pharmaceutical industry increases and as their structural complexity involves some issues when classical LC conditions are employed. Attention was paid on comparing these different columns in various LC conditions (different temperatures, gradient times, and mobile phase flow rates). The comparison of the different supports was assessed considering columns characteristics (quality of packing, silanol activity, pore size, totally porous or shell particles). In this article, peptides were first analyzed with both column technologies. Similar results to those achieved with low molecular weight compounds were obtained (peak capacity >100 for tgrad around 3 min and columns dimensions of 2.1 mm id × 50 mm), but specific conditions were required (elevated temperature and the use of a volatile ion-pairing reagent, namely TFA). For peptide analysis following tryptic digestion, the goal was to improve peak capacity and resolution because of the large number of generated peptides. For this purpose, longer columns packed with porous sub-2 μm or shell sub-3 μm particles (i.e., 150 mm) and gradient times (i.e., up to 30 min) were tested. On the other hand, proteins in their intact forms have higher molecular weights (MW > 5000 Da) and a tertiary structure, thus requiring different conditions in terms of stationary phase hydrophobicity (C4vs. C18) and pore size (300 vs. 120 Å). In addition, there were issues with adsorption onto the LC system and/or the column itself. This study showed that proteins with MWs lower than 40,000 Da required chromatographic conditions close to those employed for peptide analysis. For larger proteins, a C4 300 Å stationary phase gave the best results, confirming theoretical predictions. 相似文献
736.
The Bingham fluid model was developed to represent viscoplastic materials that change from rigid bodies at low stress to viscous fluids at high stress – a process termed yielding. Such a fluid model is used in the modeling of slurries, which occur frequently in food processing and other engineering applications. 相似文献
737.
Nobilamide B is a long-acting antagonist of transient receptor potential vanilloid-1 (TRPV1), and is expected to show therapeutic potential for treatment of pain. This linear heptapeptide possesses a Z-didehydroaminobutanoic acid moiety at the C-terminus. Stereoselective construction of the didehydroamino acid moiety was successfully achieved by application of the traceless Staudinger ligation. The combination of solid-phase peptide synthesis and the Staudinger ligation allowed rapid access to not only nobilamide B, but also its macrocyclic analogue nobilamide D. 相似文献
738.
Zeynep Gültekin Elghareeb E. Elboray Moustafa F. Aly Hussien H. Abbas-Temirek Helena J. Shepherd Ronald Grigg 《Tetrahedron》2014
We report the spatially controlled, protecting group free, catalytic assembly of a library of nineteen 7-component cascade products generated from a novel planar trisallenyl 1,3,5-triazinane-2,4,6-trione core in combination with aryl iodides and amines with excellent regio and good stereoaselectivity for Z,Z,Z-isomers. 相似文献
739.
An NMR study of 10 l-alanine- and l-valine-containing peptides was carried out in the native [C2MIM][Cl], [C4MIM][Cl], [C6MIM][Cl], [C4MIM][BF4], [C4MIM][PF6], and [C4Py][BF4] ionic liquid media. A unique high sensitivity of the ionic liquid system to the nature of peptide and ability to tune solvent–solute interactions were observed in contrast to regular organic solvents. The l-valine peptides can be selectively dissolved in [C4MIM][Cl] and [C6MIM][Cl], whereas their solubility in [C2MIM][Cl] and other ionic liquids was dramatically lower. In spite of structural similarity between the amino acids, a distinct behavior was observed for the l-alanine peptides. Solvent–solute interactions with an ionic liquid impose significant changes, and NMR spectroscopy is a useful probe for the molecular-level and nanoscale organization of the studied systems. An even/odd effect of the number of amino acids in the peptide on molecular interactions in ionic liquids was observed. Enhancement of chemical properties of peptides in ionic liquids and application of ionic liquids in the separation of peptides are the areas of practical interest in the studied systems. 相似文献
740.
On the Use of a Supramolecular Coarse‐Grained Model for the Solvent in Simulations of the Folding Equilibrium of an Octa‐β‐peptide in MeOH and H2O
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Molecular dynamics (MD) simulation can give a detailed picture of conformational equilibria of biomolecules, but it is only reliable if the force field used in the simulation is accurate, and the sampling of the conformational space accessible to the biomolecule shows many (un)folding transitions to allow for precise averages of observable quantities. Here, the use of coarse‐grained (CG) solvent MeOH and H2O models to speed up the sampling of the conformational equilibria of an octa‐β‐peptide is investigated. This peptide is thought to predominantly adopt a 314‐helical fold when solvated in MeOH, and a hairpin fold when solvated in H2O on the basis of the NMR data. Various factors such as the chirality of a residue, a force‐field modification for the solute, coarse‐graining of the solvent model, and an extension of the nonbonded interaction cut‐off radius are shown to influence the simulated conformational equilibria and the agreement with the experimental NMR data for the octa‐β‐peptide. 相似文献