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91.
El Oualid F van den Elst H Leroy IM Pieterman E Cohen LH Burm BE Overkleeft HS van der Marel GA Overhand M 《Journal of combinatorial chemistry》2005,7(5):703-713
A combinatorial synthesis of oligopeptide analogues and their evaluation as protein:geranylgeranyl transferase inhibitors is presented. The combinatorial strategy is based on the random mutation, in each new generation, of one of any of the four amino acid building blocks of which the most effective compounds of the previous generation are assembled. In this way, a progressive improvement of the average inhibitory activity was observed until the fifth generation. The most active inhibitors were found to inhibit PGGT-1 in the low micromolar range (IC(50): 3.8-8.1 microM). 相似文献
92.
The recent torsional oscillator results of Kim and Chan suggest a supersolid phase transition in solid 4He confined in Vycor. We have used a capacitive technique to directly monitor density changes for helium confined in Vycor at low temperature and have used a piezoelectrically driven diaphragm to study the pressure-induced flow of solid helium into the Vycor pores. Our measurements showed no indication of a mass redistribution in the Vycor that could mimic supersolid decoupling and put an upper limit of about 0.003 microm/s on any pressure-induced supersolid flow in the pores of Vycor. 相似文献
93.
94.
Grotenbreg GM Kronemeijer M Timmer MS El Oualid F van Well RM Verdoes M Spalburg E van Hooft PA de Neeling AJ Noort D van Boom JH van der Marel GA Overkleeft HS Overhand M 《The Journal of organic chemistry》2004,69(23):7851-7859
A practical gram-scale and high-yielding synthesis of the antimicrobial peptide gramicidin S is presented. An Fmoc-based solid-phase peptide synthesis protocol is employed for the generation of the linear decapeptide precursor, which is cyclized in solution to afford the target compound. The versatility of our method is demonstrated by the construction of eight gramicidin S analogues (15a-h) having nonproteinogenic sugar amino acid residues (4-7) incorporated in the turn regions. 相似文献
95.
Raunkjaer M El Oualid F van der Marel GA Overkleeft HS Overhand M 《Organic letters》2004,6(18):3167-3170
[reaction: see text] Novel highly functionalized dipeptide isosters are synthesized via a diastereoselective alkyl/arylation protocol of a glucose-derived (R)-tert-butanesulfinylimine. One of these novel sugar amino acid derivatives, a D-Ala-Ser/Thr isostere, was applied in a peptide synthesis protocol to afford a cyclic tetramer. 相似文献
96.
Renate M van WellMarlies E.A Meijer Herman S OverkleeftJacques H van Boom Gijsbert A van der Marel Mark Overhand 《Tetrahedron》2003,59(14):2423-2434
The synthesis of three methylene bridged sugar amino acids is described. Key transformations in the synthetic strategy are a CO-insertion on fully protected ribose, an aldol condensation with formaldehyde and an oxetane forming cyclisation step. A novel Leu-enkephalin analogue containing the δ-SAA 1 was prepared using standard solution phase peptide chemistry. 相似文献
97.
98.
Cholinesterase sensors based on screen-printed electrodes for detection of organophosphorus and carbamic pesticides 总被引:4,自引:0,他引:4
Ivanov A Evtugyn G Budnikov H Ricci F Moscone D Palleschi G 《Analytical and bioanalytical chemistry》2003,377(4):624-631
Cholinesterase sensors based on screen-printed electrodes modified with polyaniline, 7,7,8,8-tetracyanoquinodimethane (TCNQ), and Prussian blue have been developed and tested for detection of anticholinesterase pesticides in aqueous solution and in spiked grape juice. The influence of enzyme source and detection mode on biosensor performance was explored. It was shown that modification of the electrodes results in significant improvement of their analytical characteristics for pesticide determination. Thus, the slopes of the calibration curves obtained with modified electrodes were increased twofold and the detection limits of the pesticides were reduced by factors of 1.6 to 1.8 in comparison with the use of unmodified transducers. The biosensors developed make it possible to detect down to 2×10–8 mol L–1 chloropyrifos-methyl, 5×10–8 mol L–1 coumaphos, and 8×10–9 mol L–1 carbofuran in aqueous solution and grape juice. The optimal conditions for grape juice pretreatment were determined to diminish interference from the sample matrix.Abbreviations ChE Cholinesterase - TCNQ 7,7,8,8-Tetracyanoquinodimethane - ChO Choline oxidase - AChE Acetylcholinesterase - BChE Butyrylcholinesterase - BSA Bovine serum albumin - 2-PAM 2-Pyridine aldoxime methiodide 相似文献
99.
When waves propagate through layered structures, the phase velocity is frequency dependent (dispersive). If one wants to reconstruct the velocity variations in this medium, conventional traveltime-based tomographic methods cannot be used, since each frequency component has a different traveltime. A tomographic method is presented for reconstructing the phase velocity of guided waves in laterally varying media. The dispersive character of guided waves is explicitly accounted for by using a phase-based error criterium instead of "picked" traveltimes. Phase velocity and source waveform can be reconstructed to within a few percent, and the algorithm is shown to be robust in the presence of interference noise. When applied to seismic field data, the reconstructed phase velocity field correlates well with the topography of the area. 相似文献
100.
The reconstructed anatase TiO2(001) surface has been investigated by low-energy electron diffraction (LEED), x-ray photoelectron spectroscopy (XPS), and angle-resolved mass spectroscopy of recoiled ions (AR-MSRI). Prior investigations have observed or considered only a (1x1) unreconstructed termination for this surface with no detailed structural analysis. Our LEED results indicate a previously unobserved two-domain (1x4) reconstruction after sputtering and annealing the (1x1) surface. The XPS data for this reconstruction indicate the presence of only Ti4+. Simulations of the AR-MSRI experimental data indicate a best fit for a microfaceted surface, revealing both (103) and (1;03) surface planes. 相似文献