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71.
W. E. St. Turner C. Th. Polland C. C. Bisset und S. English 《Fresenius' Journal of Analytical Chemistry》1916,55(5-6):268-269
Ohne Zusammenfassung 相似文献
72.
73.
74.
Laura E. English Aleksandra Pajak Dr. Claire L. McMullin Dr. John P. Lowe Dr. Mary F. Mahon Dr. David J. Liptrot 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(28):e202200376
Thermolysis of a 1,3-dioxa-2-phospholane supported by the terphenyl ligand AriPr4 (AriPr4=[C6H3-2,6-(C6H3-2,6-iPr2)]) at 150 °C gives [AriPr4PO2]2 via loss of ethene. [AriPr4PO2]2 was characterised by X-ray crystallography and NMR spectroscopy; it contains a 4-membered P−O−P−O ring and is the isostructural oxygen analogue of Lawesson's and Woollins’ reagents. The dimeric structure of [AriPr4PO2]2 was found to persist in solution through VT NMR spectroscopy and DOSY, supported by DFT calculations. The addition of DMAP to the 1,3-dioxa-2-phospholane facilitates the loss of ethene to give AriPr4(DMAP)PO2 after days at room temperature, with this product also characterised by X-ray crystallography and NMR spectroscopy. Replacement of the DMAP with pyridine induces ethene loss from the 1,3-dioxa-2-phospholane to provide gram-scale samples of [AriPr4PO2]2 in 75 % yield in 2 days at only 100 °C. 相似文献
75.
Pons T Medintz IL Wang X English DS Mattoussi H 《Journal of the American Chemical Society》2006,128(47):15324-15331
We present a single particle fluorescence resonance energy transfer (spFRET) study of freely diffusing self-assembled quantum dot (QD) bioconjugate sensors, composed of CdSe-ZnS core-shell QD donors surrounded by dye-labeled protein acceptors. We first show that there is direct correlation between single particle and ensemble FRET measurements in terms of derived FRET efficiencies and donor-acceptor separation distances. We also find that, in addition to increased sensitivity, spFRET provides information about FRET efficiency distributions which can be used to resolve distinct sensor subpopulations. We use this capacity to gain information about the distribution in the valence of self-assembled QD-protein conjugates and show that this distribution follows Poisson statistics. We then apply spFRET to characterize heterogeneity in single sensor interactions with the substrate/target and show that such heterogeneity varies with the target concentration. The binding constant derived from spFRET is consistent with ensemble measurements. 相似文献
76.
77.
Ann M. English Keith R. Plowman Ione M. Baibich James P. Hickey Ian S. Butler Gérard Jaouen Paul Lemaux 《Journal of organometallic chemistry》1981,205(2):177-183
The arene complexes, (η6-C6H6)Cr(CO)2(CX) (X = S, Se), react with excess CO gas under pressure in tetrahydrofuran at about 60° C to produce the Cr(CO)5(CX) complexes in high yield. The IR and NMR (13C and 17O) spectra of these complexes are in complete accord with the expected C4v molecular symmetry. Like the analogous W(CO)5(CS) complex, both compounds react with cyclohexylamine to give Cr(CO)5(CNC6H11). However, while W(CO)5(CS) undergoes stereospecific CO substitution with halide ions (Y? to form trans-[W(CO)4(CS)Y]?, the two chromium chalcocarbonyl complexes apparently undergo both CO and CX substitution to afford mixtures of [Cr(CO)5Y]? and trans-[Cr(CO)4(CX)Y]?. 相似文献
78.
Kovtoun SV English RD Cotter RJ 《Journal of the American Society for Mass Spectrometry》2002,13(2):135-143
Compared to continuous extraction, pulsed extraction (PE) of ions formed by matrix-assisted laser desorption/ionization (MALDI) in time-of-flight (TOF) mass spectrometers significantly improves mass resolution. Parameters such as extraction voltage, delay time, and correction pulse must be varied, however, to achieve optimum mass resolution over a broad mass range because the PE method is mass dependent. We previously reported a novel method, mass correlated acceleration (MCA), which we have now combined with a reflectron MALDI TOF mass spectrometer to further enhance mass resolution over a broader mass range. Unlike the PE method, MCA is not mass dependent and high resolution mass spectra can be achieved with a single tuning of instrument parameters. The ions may be brought into focus simultaneously, i.e., the multi-channel recording advantage can be more fully realized. The MCA dual-stage ion source design includes an extraction pulse region and an acceleration region that contains a time-dependent waveform correlated with mass. We demonstrate the validity of this novel technique with applications in peptide mixture analysis and protein digests of lysozyme and bovine serum albumin. 相似文献
79.
Crystals of CsSbF6 belong to the rhombohedral space groupR¯3-C
3i
2
witha=7.904(1)andc=8.261(1) Å,V=446.95 Å3,Z=3,D
c=4.11 gcm–3. The antimony atom is surrounded by six fluorine atoms in a nearly perfect octahedral configuration with Sb-F 1.875(9) Å, while 12 fluorine atoms surround the cesium atom with closest contact 3.116 Å. Polarized Raman spectra of single crystals of CsSbF6 have been obtained, and it is shown that these results can be interpreted in terms of a unimolecular rhombohedral structure. The small distortion from an octahedral arrangement for the SbF
6
–
group is clearly reflected in the spectra. The Raman results are in better agreement with the space groupR¯3m-D
3d
5
than withR¯3-C
3i
2
, but this conclusion must be regarded with caution since the two features in the vibrational spectra of CsSbF6 which can be used to distinguish between the two structures are weak and ill-defined. 相似文献
80.
We study the shape of solitary wave pulses that propagate in an infinite chain of beads initially in contact with no compression. For this system, the repulsive force between two adjacent beads is proportional to the power of the distance of approach of their centers with . It is known that solitary wave solutions exist for such a system when 1$">. We prove extremely fast, double-exponential, asymptotic decay for these wave pulses. An iterative method of solution is also proposed and is seen to work well numerically.