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21.
We present a study of single color (2 + 1) resonance-enhanced multiphoton ionization (REMPI) of H2O, D2O, and HDO via several Rydberg states lying in the energy range from 80 000 to 86 000 cm−1. Photoelectron spectra (PES) show that the corresponding cations can be vibrationally state-selected for most vibrational states. The exception is the bend of H2O+ and HDO+, where mixing in the REMPI intermediate level results in weak ion intensity and only 50% state purity. 相似文献
22.
[reaction: see text] Psymberin is a sponge-derived natural product that shows striking selectivity as a cytotoxic agent. Conformational mobility has precluded stereochemical assignment for the acyl fragment of this molecule (psymberic acid) by NMR. Herein we report stereoselective syntheses of all four stereoisomers of psymberic acid. A comparison of the acid-mediated cyclization products of these compounds to the product of psymberin's acidic methanolysis showed the stereochemical configuration of this fragment to be 4S,5S. 相似文献
23.
Peter LM Riley DJ Tull EJ Wijayantha KG 《Chemical communications (Cambridge, England)》2002,(10):1030-1031
CdS quantum dots can be self-assembled on high surface area nanocrystalline TiO2 electrodes; spectroscopic and photoelectrochemical studies indicate that the size, and hence the absorption edge, of the CdS particles can be controlled; efficient photosensitization of the TiO2 electrode by the Q-particles has been achieved. 相似文献
24.
The synthesis of 3-pyridyl biaryl systems can be readily achieved by means of palladium-catalyzed Suzuki cross-coupling reactions between aryl halides and 3-pyridylboroxin. A series of cross-couplings were conducted in order to investigate the scope and limitations of this protocol. 相似文献
25.
Micklefield J 《Chemistry & biology》2005,12(6):611-613
(2S)-4-amino-2-hydroxybutyrate (AHBA) is a side chain that is important for the antibiotic activities of aminoglycosides. The elucidation of the biosynthetic pathway to AHBA, by Spencer et al. in this issue of Chemistry & Biology [1], reveals several surprises and will facilitate biosynthetic engineering of new improved aminoglycoside antibiotics. 相似文献
26.
A computational study has been performed to examine the reactions of a model beta-diketiminatoaluminium (I) complex with the hydrogen atom and with the electron. It was found that the hydrogen atom adds to the metal centre exothermically (DeltaH(rxn)=-202 kJ mol(-1)), and the spin density in the resulting radical resides entirely on the beta-diketiminato ligand. The spin density of the corresponding radical anion is very similar to the H-adduct. 相似文献
27.
Keiper JS Behles JA Bucholz TL Simhan R DeSimone JM Lynn GW Wignall GD Melnichenko YB Frielinghaus H 《Langmuir : the ACS journal of surfaces and colloids》2004,20(4):1065-1072
Anionic phosphodiester surfactants, possessing either two fluorinated chains (F/F) or one hydrocarbon chain and one fluorinated chain (H/F), were synthesized and evaluated for solubility and self-assembly in liquid and supercritical carbon dioxide. Several surfactants, of both F/F and H/F types and having varied counterions, were found to be capable of solubilizing water-in-CO2 (W/C), via the formation of microemulsions, expanding upon the family of phosphate fluorosurfactants already found to stabilize W/C microemulsions. Small-angle neutron scatteringwas used to directly characterize the microemulsion particles at varied temperatures, pressures, and water loadings, revealing behavior consistent with previous results on W/C microemulsions. 相似文献
28.
Recent analytical innovations for nucleic acid detection have revolutionized the biological sciences. Single nucleic acid sequence detection methods have been expanded to incorporate multiplexed detection strategies. A variety of nucleic acid detection formats are now available that can address high throughput genomic interrogation. Many of these parallel detection platforms or arrays, employ fluorescence as the signaling method. Fluorescence-based assays offer many advantages, including increased sensitivity, safety and multiplexing capabilities, as well as the ability to measure multiple fluorescence properties. Multiplexed microarray platforms provide parallel detection capabilities capable of measuring thousands of simultaneous responses. This review will discuss both single target detection and microarray applications with a focus on gene expression and pathogenic microorganism (PM) detection. 相似文献
29.
Bianconi PA Joray SJ Aldrich BL Sumranjit J Duffy DJ Long DP Lazorcik JL Raboin L Kearns JK Smulligan SL Babyak JM 《Journal of the American Chemical Society》2004,126(10):3191-3202
The synthesis of poly(hydridocarbyne), one of a class of carbon-based random network polymers and a structural isomer of polyacetlyene, is reported. The network backbone of this polymer is primarily composed of tetrahedrally hybridized carbon atoms, each bearing one hydride substituent and linked via three carbon-carbon single bonds into a three-dimensional random network of fused rings. This atomic-level carbon network backbone confers unusual properties on the polymer, including facile thermal decomposition to form diamond or diamond-like carbon high-quality films at atmospheric pressure, by direct deposition or by chemical vapor deposition (CVD), without the use of hydrogen or any other reagent. 相似文献
30.
Commercially available Ti(NMe(2))(4) has been used effectively as a precatalyst in a facile protocol for the intramolecular hydroamination of aminoalkenes to yield pyrrolidine and piperidine heterocyclic products with isolated yields up to 92%. Geminally substituted substrates display the highest reactivity. This precatalyst is also effective for the hydroamination of activated internal alkenes, providing access to more complex heterocyclic target molecules. 相似文献