- Pressurized sample infusion: An easily calibrated, low volume pumping system for ESI-MS analysis of reactions
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Pressurized sample infusion (PSI) continuously delivers solution from a flask through capillary tubing at a flow rate that makes it suitable as a low internal volume pumping method for electrospray ionization mass spectrometry (ESI-MS). The flow rate can be predicted from the applied pressure by using the Hagen-Poiseuille equation, but variability in internal diameter of the PEEK tubing used is such that each individual length should be calibrated if accurate results are sought. Once calibrated, the values hold well for different solvents across a range of pressures. The technique has been exemplified in two reactions: the deprotection of a protected amino acid using trifluoroacetic acid, and in the platinum-catalyzed redistribution of two silanes. In both cases, the abundances of starting material, product(s) and intermediates were tracked in real time as the reaction proceeded.
- Vikse, Krista L.,Ahmadi, Zohrab,Luo, Jingwei,Van Der Wal, Nicole,Daze, Kevin,Taylor, Nichole,McIndoe, J. Scott
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Read Online
- New TFA-free cleavage and final deprotection in Fmoc solid-phase peptide synthesis: Dilute HCl in fluoro alcohol
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A novel method for cleaving from resin and removing acid-labile protecting groups for the Fmoc solid-phase peptide synthesis is described. 0.1 N HCl in hexafluoroisopropanol or trifluoroethanol cleanly and rapidly removes the tert-butyl ester and ether, Boc, trityl, and Pbf groups and cleaves the common resin linkers: Wang, HMPA, Rink amide, and PAL. Addition of just 5-10% of a hydrogen-bonding solvent considerably retards or even fully inhibits the reaction. However, a non-hydrogen-bonding solvent is tolerated.
- Palladino, Pasquale,Stetsenko, Dmitry A.
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supporting information
p. 6346 - 6349
(2013/02/25)
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- Liquid-chromatography quantitative analysis of 20 amino acids after derivatization with FMOC-CI and its application to different origin Radix isatidis
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We developed a simple, rapid and reliable method for determination of 20 common amino acids based on derivatization with 9-fluorenylmethyl chloroformate (FMOC-CI) and RP-LC/UV, this method was first introduced into quantitative analysis of amino acids. The amino groups of amino acids were trapped with FMOC-CI to form amino acid-FMOC-Cl adducts which can be suitable for LC-UV. Chromatographic separation was performed on a C18 column with a mobile phase gradient consisting of acetonitrile and sodium acetate solution. This method was shown to be sensitive for 20 common amino acids. In the intra-day precisions assay, the range of RSDs was 3.21-7.67% with accuracies of 92.34-102.51%; for the inter-day precisions assay, the range of RSDs was 5.82-9.19% with accuracies of 90.25-100.63%. The results also indicated that solutions of amino acids-FMOC-Cl can be kept at room temperature for at least 24 h without showing significant losses in the quantified values. The validated method was successfully applied to the determination of major four kinds of amino acids in R. isatidis samples (Arg, Pro, Met and Val). The total content of amino acids in different origin R. isatidis was 13.32-19.16 mg/g. The differences between R. isatidis samples were large using HCA.
- Zhou, Wei,Zhang, Xiao-Yan,Duan, Geng-Li
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experimental part
p. 509 - 515
(2012/01/04)
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- Synthesis of an arginine tagged [Cys155-Arg180] fragment of NY-ESO-1: elimination of an undesired by-product using 'In house' resins
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During the solid-phase synthesis of a peptide fragment derived from the cancer protein NY-ESO-1 incorporating a solubilising arginine tag, a significant by-product was obtained that lacked the arginine tag. The formation of this by-product (and others) wa
- Harris, Paul W.R.,Brimble, Margaret A.
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experimental part
p. 3460 - 3466
(2010/04/05)
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- Efficient procedure for the preparation of oligomer-free N-fmoc amino acids
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A two-step method is presented for the peptide-free, high-purity, and high-yield synthesis of N-Fmoc amino acids. The first step involves the preparation of stable dicyclohexylammonium-amino acid ionic adduct in acetone. Subsequently, the ionic adducts, on reaction with Fmoc-Nosu under mild alkaline conditions, give dipeptide-free N-Fmoc amino acids. The positive charge of the dicyclohexylammonium counterion in the ionic salt has a longer radius, moderating the nucleophilicity of the carboxylate ion of the amino acid and preventing by-products by arresting the formation of mixed anhydrides, the precursors of oligopeptide impurities.
- Nowshuddin, Shaik,Rao,Reddy, A. Ram
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experimental part
p. 2022 - 2031
(2009/11/30)
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- Facile solid-phase synthesis of sulfated tyrosine-containing peptides: Total synthesis of human big gastrin-II and cholecystokinin (CCK)-39
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Chemical synthesis of tyrosine O-sulfated peptides is still a laborious task for peptide chemists because of the intrinsic acid-lability of the sulfate moiety. An efficient cleavage/deprotection procedure without loss of the sulfate is the critical difficulty remaining to be solved for fluoren-9-ylmethoxycarbonyl (Fmoc)-based solid-phase synthesis of sulfated peptides. To overcome the difficulty, TFA-mediated solvolysis rates of a tyrosine O-sulfate [Tyr(SO3H)] residue and two protecting groups, tBu for the hydroxyl group of Ser and 2,2,4,6,7-pentamethyldihydrobenzofuran-5-sulfonyl (Pbf) for the guanidino group of Arg, were examined in detail. The desulfation obeyed first-order kinetics with a large entropy (59.6 J·K-1·mol-1) and enthalpy (110.5 kJ·mol-1) of activation. These values substantiated that the desulfation rate of the rigidly solvated Tyr(SO3H) residue was strongly temperature-dependent. By contrast, the SN1-type deprotections were less temperature-dependent and proceeded smoothly in TFA of a high ionizing power. Based on the large rate difference between the desulfation and the SN1-type deprotections in cold TFA, an efficient deprotection protocol for the sulfated peptides was developed. Our synthetic strategy for Tyr(SO3H)containing peptides with this effective deprotection protocol is as follows: (i) a sulfated peptide chain is directly constructed on 2-chlorotrityl resin with Fmoc-based solid-phase chemistry using Fmoc-Tyr(SO3Na)-OH as a building block; (ii) the protected peptide-resin is treated with 90% aqueous TFA at 0 °C for an appropriate period of time for the cleavage and deprotection. Human cholecystokinin (CCK)-12, mini gastrin-II (14 residues), and little gastrin-II (17 residues) were synthesized with this method in 26-38% yields without any difficulties. This method was further applied to the stepwise synthesis of human big gastrin-II (34 residues), CCK-33 and -39. Despite the prolonged acid treatment (15-18 h at 0 °C), the ratios of the desulfated peptides were less than 15%, and the pure sulfated peptides were obtained in around 10% yields.
- Kitagawa,Aida,Fujiwara,Yagami,Futaki,Kogire,Ida,Inoue
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- Apparatus and methods for detecting antibodies
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A single, unitary, solid phase support apparatus having a planar surface divided into a plurality of separate zone functions to detect antibodies. Each zone has bonded to it, a different peptide through its C-terminal end. The zones are incubated with the analyte sample and observed for reaction, indicating the virus-specific or bacteria specific presence or absence.
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- Two New Protecting Groups for the Guanidino Function of Arginine
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Two new synthons, Fmoc-L-Arg(biphenyl-4-sulphonyl)-OH (8) and Fmoc-Arg(4-methoxy-3-t-butylbenzenesulphonyl)-OH (14), are prepared for the synthesis of arginine-containing peptides.These groups are cleaved by commonly employed trifluoroacetic acid and methanesulphonic acid.Kinetic studies reveal that extended bicyclic aromatic conjugation, as in biphenyl, slightly improves the acid lability compared to the electron-donating t-butyl group.
- Ali, Syed Safdar,Khan, Khalid Mohammed,Echner, Hartmut,Voelter, Wolfgang,Hasan, Mashooda,Atta-ur-Rahman
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- Factors Influencing the Acid Lability of Substituted Arylsulphonyl Arginine Protecting Groups
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The kinetics of hydrolysis of new, NG-protected 2,4,6-triisopropylbenzene-sulphonyl (6), 4-methoxy-3,5-di-tert-butylbenzenesulphonyl (12) and phenanthrene-3-sulphonyl (17) Fmoc derivatives of L-arginine (1) in comparison with commercially available Fmoc-Arg(Mtr)-OH (Mtr = 4-methoxy-2,3,6-trimethyl-benzenesulphonyl (2)) are studied.The acid lability of the arylsulphonyl group is decreasing as follows Mtr > Tip > Mtbs > Phen.The effect of electron-donating alkyl groups as substituents in increasing the acid lability of the arylsulphonyl residue seems to be in the order of methyl > isopropyl > tert-butyl, while the effect of extended delocalization does not appreciably increase the acid lability. - Keywords: 2,4,6-Triisopropylbenzenesulphonyl (Tip), 4-methoxy-3,5-di-tert-butylbenzenesulphonyl (Mtbs), Phenanthrene-3-sulphonyl (Phen) Residues
- Ali, Syed Safdar,Echner, Hartmut,Khan, Khalid Mohammed,Schroeder, Christoph,Hasan, Mashooda,et al.
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p. 1425 - 1433
(2007/10/02)
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