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991.
N.H. Zhang Z.Q. Tan J.J. Li W.L. Meng L.W. Xu 《Current Opinion in Colloid & Interface Science》2011,16(6):592-596
The microcantilever approach has attracted considerable attention in recent years as a means of label-free detection of a variety of biomolecular and chemical reactions. The underlying physics of the intermolecular interactions that result in mechanical motions is yet to be fully explored, but it seems both rich in science and of technological importance. This paper presents an overview of experiments and theories related to interactions of single-stranded DNA immobilized on microcantilevers. Experiments and theories show that, at high grafting density, hydration forces are the dominant factor determining cantilever deflections, not electrostatics or conformational entropy. 相似文献
992.
Kovacs JM Mant CT Kwok SC Osguthorpe DJ Hodges RS 《Journal of chromatography. A》2006,1123(2):212-224
Side-chain backbone interactions (or "effects") between nearest neighbours may severely restrict the conformations accessible to a polypeptide chain and thus represent the first step in protein folding. We have quantified nearest-neighbour effects (i to i+1) in peptides through reversed-phase liquid chromatography (RP-HPLC) of model synthetic peptides, where L- and D-amino acids were substituted at the N-terminal end of the peptide sequence, adjacent to a L-Leu residue. These nearest-neighbour effects (expressed as the difference in retention times of L- and D-peptide diastereomers at pHs 2 and 7) were frequently dramatic, depending on the type of side-chain adjacent to the L-Leu residue, albeit such effects were independent of mobile phase conditions. No nearest-neighbour effects were observed when residue i is adjacent to a Gly residue. Calculation of minimum energy conformations of selected peptides supported the view that, whether a L- or D-amino acid is substituted adjacent to L-Leu, its orientation relative to this bulky Leu side-chain represents the most energetically favourable configuration. We believe that such energetically favourable, and different, configurations of L- and D-peptide diastereomers affect their respective interactions with a hydrophobic stationary phase, which are thus quantified by different RP-HPLC retention times. Side-chain hydrophilicity/hydrophobicity coefficients were generated in the presence of these nearest-neighbour effects and, despite the relative difference in such coefficients generated from peptides substituted with L- or D-amino acids, the relative difference in hydrophilicity/hydrophobicity between different amino acids in the L- or D-series is maintained. Overall, our results demonstrate that such nearest-neighbour effects can clearly restrict conformational space of an amino acid side-chain in a polypeptide chain. 相似文献
993.
Rapid simultaneous determination of four anthracene derivatives using a single non-linear variable-angle synchronous fluorescence spectrum 总被引:1,自引:0,他引:1
A rapid, simple and inexpensive spectrofluorimetric method has been developed for the simultaneous identification and quantification of anthracene (ANT), 9,10-dimethylanthracene (DIM), 2-aminoanthracene (AMI) and dibenz[ah]anthracene (DIB). A well-resolved spectrum for the mixture of these four compounds is obtained based on a single non-linear variable-angle synchronous scanning. The linear concentration ranges are 10-1,000, 5-500, 50-1,000 and 10-200 ng mL(-1) for ANT, DIM, AMI and DIB, respectively, at lambdaex/lambdaem = 358/380, 399/408, 414/465 and 298/394 nm, respectively. The analyses are performed in cyclohexane. Recoveries of 90.0-111.0% in synthetic mixtures are obtained. The detection limits are 2.0 ng mL(-1) for DIM, 2.7 ng mL(-1) for ANT, 15.8 ng mL(-1) for AMI and 4.2 ng mL(-1) for DIB. The method has also been applied to several real water samples with satisfactory results. 相似文献
994.
A diode end-pumped single-frequency Tm,Ho:YAP laser at room temperature was reported. We obtain a single frequency Tm,Ho:YAP
laser of up to 31 mW with Fabry-Perot etalons in the cavity at 2130.8 nm. The optical conversion efficiency is 1.0% and the
slope efficiency is 6.3%. The measured full width at half maximum (FWHM) is approximately 65 pm. The single-longitudinal-mode
(SLM) laser can be used as a seed laser for coherent wind measurements and differential absorption LIDAR systems. 相似文献
995.
J. Q. Gao T. Wu J. Wang Y. Bai S. J. Wang Y. N. Xu Y. Li X. D. Zhang 《Russian Journal of Coordination Chemistry》2012,38(7):491-500
Two novel rare-earth metal complexes, namely, mononuclear Na4[EuIII(Dtpa)(H2O)]2 · 11.5H2O (I) and binuciear (NH4)4[EuIII(Dtpa)]2 · 10H2O (II) (H5Dtpa = diethylenetriamine-N,N,N??,N??,N??-pentaacetic acid), have successfully been synthesized and characterized by infrared spectrum, UV-Vis spectrum, fluorescence spectrum, thermal analysis, and single-crystal X-ray diffraction techniques. Since these two Eu(III) complexes have different counterions, causing different coordination environment, fluorescence spectrum analysis displays different fluorescence properties. X-ray diffraction reveals that the coordination polyhedra of both complexes adopt pseudo-D 3h tricapped trigonal prismatic conformation. However, I is a nine-coordinate mononuclear complex and crystallizes in the monoclinic crystal space group P21/n and II is a nine-coordinate binuciear complex and crystallizes in the triclinic crystal space group $P\bar 1$ . In addition, II has two independent binuciear structural units, [Eu(1)2(Dtpa)2] and [Eu(2)2(Dtpa)2]. Along the yz plane both [Eu(1)2(Dtpa)2] and [Eu(2)2(Dtpa)2] form a 1D chain structure, respectively. Further, along the y axis linking of each other forms a 2D planar structure. 相似文献
996.
Na Z Li L Uttamchandani M Yao SQ 《Chemical communications (Cambridge, England)》2012,48(58):7304-7306
A microarray immobilized with 105 aldehyde-containing small molecules was screened against mammalian cell lysates over-expressing cathepsin L to identify two potent inhibitors, which were subsequently converted into cell-permeable probes capable of live-cell imaging of endogenous cysteinyl cathepsin activities by two-photon fluorescence microscopy. 相似文献
997.
Q. L. Zhang X. H. Tian J. Y. Sun Y. Z. Yuan K. T. Zhang 《Polymer Science Series A》2017,59(5):708-717
Nanoparticles including starch-graft-methylmethacrylate, starch-graft-(methylmethacrylate/methyl acrylate), starch-graft-(methyl methacrylate/butyl methacrylate) were synthesized via emulsifier-free emulsion polymerization and were blended with natural rubber latex at various mass ratios. Chemical structure of graft copolymers was confirmed by Fourier transform infrared. Transmission electron microscopy demonstrated the core-shell structures of the nanoparticles distributed uniformly around the natural rubble particles. The tensile strength of blend films was significantly enhanced by addition of graft copolymers. Besides, scanning electron microscopy and atomic force microscopy showed the blend film had smooth surface. 相似文献
998.
999.
J. Q. Di X. D. Xu D. Z. Li D. H. Zhou F. Wu Z. W. Zhao J. Xu D. Y. Tang 《Laser Physics》2011,21(10):1742-1744
Three mixed crystals, Nd:GdYAG, Nd:LuYAG, and Nd:GdLuAG, were grown by Czochralski method. We report the continuous-wave (CW)
Nd:GdYAG, Nd:LuYAG, and Nd:GdLuAG laser operation under laser diode pumping. The maximum output powers are 4.11, 5.31, and
7.47 W, with slope efficiency of 73.0, 55.3, and 57.1%, respectively. With replacing Lu3+ or Y3+ ions with large Gd3+ ions, the pump efficiency increases. 相似文献
1000.
Self-induced phase matching in stimulated four-wave mixing in a nonbirefringent single-mode optical fiber has been observed. It is shown that in a nonbirefringent single-mode fiber the phase matching that is necessary for stimulated four-wave mixing can be accomplished with a combination of self-phase modulation and cross-phase modulation induced by a pump-laser pulse. 相似文献