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941.
942.
Kerry J. Lee Lauren M. Browning Tao Huang Feng Ding Prakash D. Nallathamby Xiao-Hong Nancy Xu 《Analytical and bioanalytical chemistry》2010,397(8):3317-3328
Currently, molecular mechanisms of multidrug ABC (ATP-binding cassette) membrane transporters remain elusive. In this study,
we synthesized and characterized purified spherically shaped silver nanoparticles (Ag NPs) (11.8 ± 2.6 nm in diameter), which
were stable (non-aggregation) in PBS buffer and inside single living cells. We used the size-dependent localized surface plasmon
resonance (LSPR) spectra of single Ag NPs to determine their sizes and to probe the size-dependent transport kinetics of the
ABC (BmrA, BmrA-EGFP) transporters in single living cells (Bacillus subtilis) in real time at nanometer resolution using dark-field optical microscopy and spectroscopy (DFOMS). The results show that
the smaller NPs stayed longer inside the cells than larger NPs, suggesting size-dependent efflux kinetics of the membrane
transporter. Notably, accumulation and efflux kinetics of intracellular NPs for single living cells depended upon the cellular
expression level of BmrA, NP concentrations, and a pump inhibitor (25 μM, orthovanadate), suggesting that NPs are substrates
of BmrA transporters and that passive diffusion driven by concentration gradients is the primary mechanism by which the NPs
enter the cells. The accumulation and efflux kinetics of intracellular NPs for given cells are similar to those observed using
a substrate (Hoechst dye) of BmrA, demonstrating that NPs are suitable probes for study of multidrug membrane transporters
of single living cells in real-time. Unlike fluorescent probes, single Ag NPs exibit size-dependent LSPR spectra and superior
photostability, enabling them to probe the size-dependent efflux kinetics of membrane transporters of single living cells
in real-time for better understanding of multidrug resistance. 相似文献
943.
The electronic structure and one‐ and two‐photon absorption spectra of four fluorophores, p‐bis(o‐methoxystyryl)benzene (Bis‐MSB), coumarin 307, fluorescein and rhodamine B, commonly used as reference compounds for two‐photon absorption spectra, have been theoretically calculated and compared with available experimental data. The possible reasons for the wide discrepancies in two‐photon absorption cross‐sections reported in the literature are discussed on the basis of the theoretical findings. The role of a solvent environment on the electronic one‐ and two‐photon absorption spectra is also studied. We highlight some necessary precautions that one needs to take when comparing literature results of two‐photon absorption cross‐sections. 相似文献
944.
Arasambattu K. Mohanakrishnan Neelamegam Ramesh Chandran Prakash 《Tetrahedron letters》2005,46(41):6983-6985
A novel dimerization of N-protected bromomethylindoles involving an exchange reaction with phenylmagnesium chloride is reported. 相似文献
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950.
Richard F. Blute Ivan T. Ivanov Prakash Panangaden 《International Journal of Theoretical Physics》2003,42(9):2025-2041
We give a mathematical framework to describe the evolution of open quantum systems subject to finitely many interactions with classical apparatuses and with each other. The systems in question may be composed of distinct, spatially separated subsystems which evolve independently, but may also interact. This evolution, driven both by unitary operators and measurements, is coded in a mathematical structure in such a way that the crucial properties of causality, covariance, and entanglement are faithfully represented. The key to this scheme is the use of a special family of spacelike slices—we call them locative—that are not so large as to result in acausal influences but large enough to capture nonlocal correlations. 相似文献