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排序方式: 共有370条查询结果,搜索用时 15 毫秒
281.
David?W?BollivarEmail author Cheryl?Clauson Rachel?Lighthall Siiri?Forbes Bashkim?Kokona Robert?Fairman Lenka?Kundrat Eileen?K?Jaffe 《BMC biochemistry》2004,5(1):17
Background
The enzyme porphobilinogen synthase (PBGS), which is central to the biosynthesis of heme, chlorophyll and cobalamins, has long been known to use a variety of metal ions and has recently been shown able to exist in two very different quaternary forms that are related to metal ion usage. This paper reports new information on the metal ion independence and quaternary structure of PBGS from the photosynthetic bacterium Rhodobacter capsulatus. 相似文献282.
283.
E. Molos A. Stock G. Ritter J. M Calvera G. P. Baxter H. W. Strackweather O. Hönigsehmid E. Zintl P. Thilo Th. W. Richards H. H. Willard O. Forbes S. Bedr Can L. Birekenbach H. Grimm J. Goubeau H. V. A. Briscoe P. L. Robinson H. C. Smith H. Auer v. Welsbach W. Prandtl A. Q. Butler K. R. Krishnaswani S. D. Muzaffar F. W. Aston 《Analytical and bioanalytical chemistry》1928,73(7-8):296-299
284.
When presented with a mixture of intact proteins, electrospray ionization with Fourier-transform mass spectrometry (ESI-FTMS) has the capability to obtain direct fragmentation information from isolated ions. However, the automation of this capability has not been achieved to date. We have developed software for unattended acquisition of protein tandem mass spectrometry (MS/MS) data and batch processing of the resulting files for identification of whole proteins. Mixtures of both protein standards (8-29 kDa) and Methanococcus jannaschii cytosolic proteins (up to six components + 20 kDa) were infused via an autosampler, and MS/MS data were acquired without human intervention. The acquisition software recognizes ESI charge state patterns, generates protein-specific isolation waveforms on-the-fly, and fragments ions using two different infrared laser times. In addition to protein standards, five wild-type proteins (7-14 kDa) were identified automatically with 100% sequence coverage from the M. jannaschii database. The software underpins a measurement platform for sample-dependent acquisition of MS/MS data for whole proteins, a critical step to realize proteomics with 100% sequence coverage in a higher throughput setting. 相似文献
285.
Clegg W Forbes GC Kennedy AR Mulvey RE Liddle ST 《Chemical communications (Cambridge, England)》2003,(3):406-407
While neither KHMDS nor Zn(HMDS)2 can unilaterally metallate toluene under the conditions studied, the bilateral base 'KZn(HMDS)3' can smoothly do so to produce the benzyl product [[KZn(HMDS)2(CH2Ph)]infinity], which exists in the crystal as an infinite spiral chain of benzyl (ambi-sigma, pi)-linked (KNZnN) rings. 相似文献
286.
Malcolm D. E. Forbes 《Photochemistry and photobiology》1997,65(1):73-81
Abstract— Steady-state and time-resolved electron paramagnetic resonance (TREPR) experiments are described. Comparison of the TREPR continuous wave method to other time domain EPR techniques such as Fourier transform EPR (FT-EPR) is made, and the advantages and disadvantages of each are presented. The role played by several mechanisms of chemically induced dynamic electron spin polarization (CIDEP) in the appearance of the spectra is explained. The advantages of using higher frequency spectrometers than the standard X-band (9.5 GHz) are presented and discussed. Examples are presented that are relevant to organic photochemistry and electron donor-acceptor chemistry. The use of TREPR to study polymer photodegradation, polymer chain dynamics, free radical initiator chemistry and biradical spin exchange interactions is described. Emphasis is placed on magnetic field effects studied by multiple frequency TREPR in these systems. Finally, several future directions in the field are discussed in terms of new developments in microwave and magnetic field technology. 相似文献
287.
We report the first experimental study of chemically induced electron spin polarization (CIDEP) processes in low magnetic fields for spin-correlated radical pairs (SCRPs) in micellar environments. Photoexcitation of (2,4,6-trimethylbenzoyl) diphenylphosphine oxide (TMBDPO) leads to the radical pair comprised of acyl radical 1 and phosphonyl radical 2. The spin polarization, which is very strong in free solution even at zero field, was detected using L-band time-resolved electron paramagnetic resonance (TREPR) spectroscopy with specially modified resonators. The mechanism of formation and decay of low field CIDEP in SCRPs is presented and discussed. The prominent difference between low and high field spectra in micelles is the absence of anti-phase structure for radical 2 with HFI a > B0. This feature is consistent with the proposed polarization mechanism and theoretical predictions. 相似文献
288.
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290.
Daisuke Tanaka Shungo Harajiri Yuto Fujita Kayn A. Forbes Tien Thanh Pham David L. Andrews 《Laser \u0026amp; Photonics Reviews》2024,18(4):2300536
Plasmonic interactions between an asymmetrically coated core–shell (ACCS) nanoparticle and an optical vortex produce a novel engagement of the spin angular momentum (SAM) and the orbital angular momentum (OAM) of the input. Simulations based on a discrete dipole approximation (DDA) indicate that the SAM and the OAM of the incident beam determine the modal order of resonance, correctly identifying the peak wavelength, and both the direction and magnitude of optical torque exerted upon the excited, localized plasmon resonance in the ACCS particle. These simulations also indicate higher-order resonances, including hexapole and octupole modes, and a zero-order resonance (expressible as a monopole mode), can be excited by judicious selection of the SAM and OAM. A detailed symmetry analysis shows how the multipoles associated with eigenmode excitations connect to the radiation multipoles at the heart of the multipole expansion. It is also shown how additional, distorted resonance modes due to the asymmetricity of the structure are also exhibited. These specific plasmonic characteristics, which cannot be realized by plane wave excitation, become possible through the ACCS asymmetry engaging with the distinct optical vortex nature of the excitation. 相似文献