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991.
Yuanzhong Yang Reinhard I. BoysenSimon J. Harris Milton T.W. Hearn 《Journal of chromatography. A》2009,1216(18):3767-3773
This investigation describes the separation of tryptic peptides by capillary reversed-phase high-performance liquid chromatography (RP-HPLC) with eluents in the intermediate pH range, followed by in-line electrospray ionisation tandem mass spectrometry (ESI-MS/MS) analysis. For these purposes, gradient elution procedures with an aqueous eluent containing 20 mM ammonium formate, and an increasing content of acetonitrile or methanol, were employed. Compared to the analysis of the same tryptic peptides under low-pH conditions with an ion-pairing reagent, the increase in the pH with the 20 mM ammonium formate mobile phase led to significant changes in both peptide retention to the reversed-phase column and the collision-induced dissociation at the MS/MS stage as a consequence of the changes in the physico-chemical properties of these peptides, such as their overall charge, polarity and relative hydrophobicity. Thus, improved selectivity for the peptide separation and favourable tandem mass spectrometry analysis could be obtained with eluents in this intermediate pH range. The number of tryptic peptides identified by the new approach for the proteins investigated were significantly higher than that obtained by the conventional low-pH methods. Moreover, analysis of protein digests at very low concentrations was also performed under both acidic and intermediate pH conditions and similar improvements in selectivity and MS/MS detection limits were observed, i.e. identification of more distinct peptides and higher sequence coverage of the protein was obtained when eluents of intermediate pH were employed. This study therefore highlights the potential of conducting peptide mapping in the intermediate pH range to achieve more reliable and sensitive protein identifications with capillary RP-HPLC–ESI-MS/MS. 相似文献
992.
The synthesis of 6,7-diacylcoumarins is reported via the oxidation of 6-acetyl-7-hydroxycoumarin N-acylhydrazones with lead tetraacetate. The procedure involves transformation of hydroxy into an acyl group and formation of a new C–C bond. 相似文献
993.
Partridge Ashton Harris Paul Hirotsu Toshihiro Kurosawa Shigeru 《Plasmas and Polymers》2000,5(3-4):191-200
The paper describes attempts to apply plasma polymers to the development of chemical sensors. The plasma polymers were used as membranes to coat conventional conducting polymer sensors, as stand-alone chemiresistive sensors and as absorbent coatings on quartz crystal microbalances. The plasma polymers were derived from combinations of pyrrole and three silicon containing monomers. In the chemiresistive sensors, conductivity was induced in the polymer matrix by doping with iodine. The paper describes the experimental polymerization conditions, the physical characteristics of the polymers, and the application of the different polymers to sensing common volatile analytes. 相似文献
994.
Maly DJ Leonetti F Backes BJ Dauber DS Harris JL Craik CS Ellman JA 《The Journal of organic chemistry》2002,67(3):910-915
A highly efficient solid-phase synthesis method for the preparation of fluorogenic protease substrates based upon the bifunctional leaving group 7-amino-4-carbamoylmethylcoumarin (ACC) is reported. Methods for the large-scale preparation of the novel fluorogenic leaving-group ACC are provided (Scheme 1). Detailed procedures are also provided for loading a diverse set of amino acids to support-bound ACC in good yields and with minimal racemization. Finally, procedures are included for the preparative synthesis of optimized ACC substrates for HIV-1 protease and plasmin. 相似文献
995.
Ajit K. Mahapatra Donna L. Harris Chau N. Nguyen Govind Kannan 《Journal of Electrostatics》2011,69(1):30-35
Low-voltage direct current was applied to beef, inoculated with Escherichia coli O157:H7 on the surface covered with a thin film of 0.15 M NaCl solution. Experiments were conducted with 15, 30, and 45 mA/cm2 currents; 1, 10 and 100 kHz frequencies; 30, 50 and 70% duty cycles, and 2, 8 and 16 min treatment durations. Increase in current intensity, frequency, duty cycle, and treatment duration increased the % reduction of E. coli. A maximum reduction of 98.9% was achieved. Sensory color analysis showed significant differences between treated and untreated beef. The maximum temperature rise of NaCl solution was 31.9 °C. 相似文献
996.
Chann B Huang RK Missaggia LJ Harris CT Liau ZL Goyal AK Donnelly JP Fan TY Sanchez-Rubio A Turner GW 《Optics letters》2005,30(16):2104-2106
We demonstrate 35 W output peak power with M2 approximately 1.35 in both dimensions from a 100 element, 100 microm pitch slab-coupled optical waveguide laser diode array using wavelength beam combining. 相似文献
997.
M. Hayne A. Usher J. J. Harris C. T. Foxon 《Physica E: Low-dimensional Systems and Nanostructures》1998,1(1-4)
We have observed the quantum Hall effect in a high mobility two-dimensional electron gas to filling factors up to 80 at 0.3 K. This demonstrates the presence of both localized and extended states at low field, and explains the failure of the standard semi-classical analysis of Shubnikov–de Haas (SdH) oscillations in this regime. We go on to derive a general expression for the conductivity due to rectangular bands of extended states, and show that the observed temperature dependence of the SdH oscillations is consistent with this picture. An analysis of the oscillations using this expression reveals the predicted levitation of the extended states as the magnetic field is reduced. 相似文献
998.
Alex?K?Harris Adviye?Ergul Anna?Kozak Livia?S?Machado Maribeth?H?Johnson Susan?C?FaganEmail author 《BMC neuroscience》2005,6(1):49
Background
While gelatinase (MMP-2 and -9) activity is increased after focal ischemia/reperfusion injury in the brain, the relative contribution of neutrophils to the MMP activity and to the development of hemorrhagic transformation remains unknown. 相似文献999.
Jian-Yong Zhang Xiao Cai Xiao-Hu Mo Di-Zhou Guo Jian-Li Wang Bai-Qi Liu M. N. Achasov A. A. Krasnov N. Yu. Muchnoi E. E. Pyata E. V. Mamoshkina F. A. Harris 《中国物理C(英文版)》2016,40(7):076001-076001
The beam energy measurement system is of great importance for both BEPC-Ⅱ accelerator and BES-III detector. The system is based on measuring the energies of Compton back-scattered photons. In order to meet the requirements of data taking and improve the measurement accuracy, the system has continued to be upgraded, which involves the updating of laser and optics subsystems, replacement of a view-port of the laser to the vacuum insertion subsystem, the use of an electric cooling system for a high purity germanium detector, and improvement of the data acquisition and processing subsystem. The upgrade system guarantees the smooth and efficient measurement of beam energy at BEPC-II and enables accurate offline energy values for further physics analysis at BES-Ⅲ. 相似文献
1000.
Giang Huong Nguyen Thomas S. Dexheimer Andrew S. Rosenthal Wai Kit Chu Dharmendra Kumar Singh Georgina Mosedale Csanád Z. Bachrati Lena Schultz Masaaki Sakurai Pavel Savitsky Mika Abu Peter J. McHugh Vilhelm A. Bohr Curtis C. Harris Ajit Jadhav Opher Gileadi David J. Maloney Anton Simeonov Ian D. Hickson 《Chemistry & biology》2013,20(1):55-62