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581.
Yim Ling Mak Jia Jun Wu Wing Hei Chan Margaret B. Murphy James C. W. Lam Leo L. Chan Paul K. S. Lam 《Analytical and bioanalytical chemistry》2013,405(10):3331-3340
Ciguatera fish poisoning (CFP) is a food intoxication caused by exposure to ciguatoxins (CTXs) in coral reef fish. Rapid analytical methods have been developed recently to quantify Pacific-CTX-1 (P-CTX-1) in fish muscle, but it is destructive and can cause harm to valuable live coral reef fish. Also fish muscle extract was complex making CTX quantification challenging. Not only P-CTX-1, but also P-CTX-2 and P-CTX-3 could be present in fish, contributing to ciguatoxicity. Therefore, an analytical method for simultaneous quantification of P-CTX-1, P-CTX-2, and P-CTX-3 in whole blood of marketed coral reef fish using sonication, solid-phase extraction (SPE), and liquid chromatography tandem mass spectrometry (LC-MS/MS) was developed. The optimized method gave acceptable recoveries of P-CTXs (74–103 %) in fish blood. Matrix effects (6–26 %) in blood extracts were found to be significantly reduced compared with those in muscle extracts (suppressed by 34–75 % as reported in other studies), thereby minimizing potential for false negative results. The target P-CTXs were detectable in whole blood from four coral reef fish species collected in a CFP-endemic region. Similar trends in total P-CTX levels and patterns of P-CTX composition profiles in blood and muscle of these fish were observed, suggesting a relationship between blood and muscle levels of P-CTXs. This optimized method provides an essential tool for studies of P-CTX pharmacokinetics and pharmacodynamics in fish, which are needed for establishing the use of fish blood as a reliable sample for the assessment and control of CFP. Figure
Chromatograph of P-CTXs in whole blood of wild-caught moray eel 相似文献
582.
Bo Li Shuang-Quan Zang Can Ji Thomas C.W. Mak 《Journal of organometallic chemistry》2011,696(15-16):2820-2828
A series of five silver coordination polymers [(AgL1)·(AgCF3COO)5·(H2O)3] (1), [(AgL1)2·(AgCF3COO)11·(H2O)6] (2), [(AgL2)·(AgCF3COO)3·(H2O)] (3), [(AgL3)·(AgCF3COO)4·(CH3CN)2] (4), and [(AgL3)·(AgCF3COO)7·(CH3CN)2·(H2O)2] (5) have been constructed from three flexible anionic ligands HL1, HL2, and HL3 (HL1 = 1-chloro-2-(prop-2-ynyloxy)benzene, HL2 = 1-chloro-3-(prop-2-ynyloxy)benzene, HL3 = 1-chloro-4-(prop-2-ynyloxy)benzene). In these compounds, the invariable appearance of the μ4- and μ5-ligation modes of the ethynide moiety affirms the general utility of the flexible silver-ethynide supramolecular synthon o-, m-, p-Cl?C6H5OCH2CC?Agn (n = 4, 5) in coordination network assembly. Among them, Ag?Cl interaction plays a vital role in assembling the supramolecular structures in complexes 1?3. 相似文献
583.
A two-stage "tandem strategy" for the synthesis of benzofused nitrogen heterocycles is described that is particularly useful for the construction of systems with a high level of substitution on the benzenoid ring. The first stage in the strategy involves a benzannulation based on the reaction of cyclobutenones with ynamides. This cascade process proceeds via a sequence of four pericyclic reactions and furnishes a multiply substituted aniline derivative which can bear a variety of functionalized substituents at the position ortho to the nitrogen. In the second stage of the tandem strategy, ring-closing metathesis generates the nitrogen heterocyclic ring. This two-step sequence provides efficient access to highly substituted dihydroquinolines, benzazepines, benzazocines, and related benzofused nitrogen heterocyclic systems. The application of this chemistry in a concise formal total synthesis of the anticancer agents (+)-FR900482 and (+)-FR66979 is described. 相似文献
584.
X.T. Li P.Y. Du H. Ye C.L. Mak K.H. Wong 《Applied Physics A: Materials Science & Processing》2008,92(2):397-400
Textured LixNi2-xO (LNO) thin films have been fabricated on (001)MgO substrates by pulsed laser deposition technique. The as-deposited LNO
films shows a conductivity of 2.5×10-3 Ω m and possess a transmittance of about 35% in the visible region. Subsequent deposition of Sr0.6Ba0.4Nb2O6 (SBN60) thin film on these LNO-coated MgO substrates resulted in a textured SBN layer with a 〈001〉 orientation perpendicular
to the substrate plane. Phi scans on the (221) plane of the SBN layer indicated that the films have two in-plane orientations
with respect to the substrate. The SBN unit cells were rotated in the plane of the film by ± 8.2° as well as ± 45° with respect
to the LNO/MgO substrate. Besides the highly (00l)-orientation, the SBN films also exhibited a dense microstructure as shown
by scanning electron microscopy. The electro-optic coefficient (r33) of the SBN film was measured to be 186 pm/V. On the basis of our results, we have demonstrated that the LNO film can be
used as a buffer layer as well as a transparent bottom electrode for waveguide applications. The SBN/LNO heterostructure is
also a suitable candidate for integrated electro-optics devices.
PACS 42.79.Gn; 42.82.Et; 78.20.Ci 相似文献
585.
Marijke WA de Backer Maike AD Brans Mieneke CM Luijendijk Keith M Garner Dianne MA van den Heuvel R Jeroen Pasterkamp Roger AH Adan 《BMC neuroscience》2010,11(1):94
Background
Multiple neuropeptides, sometimes with opposing functions, can be produced from one precursor gene. To study the roles of the different neuropeptides encoded by one large precursor we developed a method to overexpress minigenes and establish local secretion. 相似文献586.
Two particular exact solutions of thegravitational field equations for a homogeneous flatFriedmann-Robertson-Walker universe filled with a causalbulk viscous fluid in the framework of the fullIsrael-Stewart-Hiscock theory are presented. The dynamics of theuniverse is entirely determined in the present models byits thermal behavior. The solutions of the fieldequations are expressed in an exact closed parametric form and correspond to an inflationarytransition between a singular state and a Minkowskianspace-time and a quasi-Minkowskian era and aninflationary state, connected by a noninflationaryphase, respectively. The inflationary era of the first solution isassociated with an increase in temperature and energydensity (a heating period), but with a decrease of thecomoving entropy. The evolutionary period described by the second solution leads during itsnoninflationary phase to a rapid decrease in thetemperature, the energy density, and the comovingentropy of the corresponding universe. 相似文献
587.
Zuowei Xie Chaoguo Yan Qingchuan Yang Thomas C. W. Mak 《Angewandte Chemie (International ed. in English)》1999,38(12):1761-1763
The tetranion ligand η7-C2B10H124− has been observed for the first time in 1 , which was obtained from the reaction of o-C2B10H12 with excess K metal followed by treatment with UCl4. As shown in the picture (without K cations and coordinated THF molecules), 1 is a centrosymmetric dimer with a bent sandwich structure. 相似文献
588.
589.
In heme‐reconstituted heme proteins, the heme inserts such that some of the heme is rotated 180° about the α–γ meso axis, eventually equilibrating to native conformations. Also, proteins from different species may naturally possess both conformers. Resonance Raman (RR) spectroscopy is effective in signaling this conformational heterogeneity, detecting altered interactions with active site residues. While shifts of the vibrational modes of the two vinyl groups could be readily detected, they could not be assigned to a particular vinyl group. This deficiency is alleviated by employing a specifically labeled protoheme isotopomer, wherein only the 4‐vinyl group is labeled (i.e. –CH=C2H2), providing a spectral editing mechanism for selectively tracking the individual vinyl groups. The RR spectral data acquired here for the met‐, deoxy‐, and ferrous CO adduct of myoglobin, along with their ‘flipped heme’ isomers, provide convincing evidence for the anticipated effects of ‘swapping’ the environments of the two vinyl groups; i.e., in the native form, the 2‐vinyl group assumes a more out‐of‐plane orientation with respect to the pyrrole plane than does the (nearly in‐plane) 4‐vinyl group, whereas in the ‘reversed’ orientation, the 4‐vinyl group now assumes a position that is more out‐of‐plane than the newly positioned 2‐vinyl group. The ability of RR spectroscopy to document such differences in the orientation of the vinyl substituents is made important by the fact that changes in the disposition of these groups has long been known to carry functional consequences. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献