Threefold parallel interwoven (6,3) nets were assembled from Ni(II) cyclam complex and 1,3,5-tris[2-(4-carboxyphenyl)-1-ethynyl]benzene. The network generates triangular voids of effective size ca. 18.4 x 14.7 x 9.5 A. It contains 35% free volume of the crystal volume and is stable up to 300 degrees C. 相似文献
An X-ray structural study of the trinuclear complex Fe3(CO)7[Pn2PC4(CF3)2 PPh2 (I) has shown that the conversion of another trinuclear complex Fe3(CO)8[Ph2PC4(CF3)2]PPh2 (II) to (I) involves intramolecular CO elimination, metalmetal bond formation and novel structural changes in a diphenylphosphide bridge. 相似文献
A rapid screening procedure is described for the simultaneous determination of 13 β-blockers in urine at the range of 0.010-1.0 μg mL−1. The procedure involves N-ethoxycarbonyl (EOC) derivatization of β-blockers in urine sample, followed by extraction and further conversion to trimethylsilyl (TMS) derivatives for the analysis by gas chromatography-mass spectrometry (GC-MS) in selected ion monitoring (SIM) mode (GC-SIM-MS). The characteristic fragment ions at m/z 260 and m/z 144, and [M − 15]+ ions permitted sensitive and selective detection of most of the β-blockers in the presence of co-extracted urinary amino alcohols at much higher levels. The whole procedure of EOC/TMS derivatization with subsequent GC-SIM-MS analysis was linear (r ≥ 0.9988). The LODs were varied from 0.03 to 2.7 ng mL−1. The ranges of precision (%relative standard deviation) and accuracy (%relative error) of the overall procedure at two different added amounts (0.02 and 0.5 μg mL−1) in urine matrix varied from 1.3 to 9.4 and from −9.6 to 9.7, respectively. The recoveries were measured to be ranged from 90.4 to 109.7%. 相似文献
The important anticancer drug Taxol (paclitaxel, PTX) owes its unique activity to its ability to bind to tubulin in a stoichiometric ratio and promote its assembly into microtubules. The conformation of the microtubule-bound drug has been the focus of numerous research efforts, since the inability of polymerized tubulin to form crystals precludes structure proof by X-ray crystallography. Likewise, although the alpha,beta-tubulin dimer structure has been solved by electron crystallography, the 3.7 A resolution is too low to permit direct determination of either ligand conformation or binding pose. In this article, we present experimental results from 2H{19F} REDOR NMR that provide direct confirmation that paclitaxel adopts a T-shaped conformation when it is bound to tubulin. 相似文献
The entrapment of a protein in porous poly(d,l ‐lactide‐co‐glycolide) (PLGA) microspheres is demonstrated through the closure of their outer surface pores for sustained delivery of the protein. The porous PLGA microspheres with less than 10 μm in size are prepared by electrospraying. Aqueous solutions containing fluorescein isothiocyanate‐dextran or bovine serum albumin (BSA) are penetrated into the inner pores as a result of vacuum treatment, and the outer surface pores of the porous PLGA microspheres are then closed using a solvent (dimethyl sulfoxide) to ensure entrapment of the macromolecules. Confocal microscopy images confirm the presence of a large amount of the macromolecules inside the porous structure. Circular dichroism spectroscopy and release analysis reveal that BSA is entrapped without denaturation and released in a sustained manner for a period of over 2 months, respectively.
A doubly interpenetrating porous metal–organic framework ( SNU‐77 ) has been synthesized from the solvothermal reaction of the extended carboxylic acid tris(4′‐carboxybiphenyl)amine (H3TCBPA) and Zn(NO3)2 ? 6H2O in N,N‐dimethylacetamide (DMA). SNU‐77 undergoes single‐crystal‐to‐single‐crystal transformations during various activation processes, such as room‐temperature evacuation, supercritical CO2 drying, and high temperature evacuation, to afford SNU‐77R , SNU‐77S , and SNU‐77H , respectively. These guest‐free MOFs exhibited different fine structures with different window shapes and different effective window sizes at room temperature. Variable‐temperature synchrotron single‐crystal X‐ray analyses reveal that the guest‐free structure is also affected by changes in temperature. Despite the different fine structures, SNU‐77R , SNU‐77S , and SNU‐77H show similar gas sorption properties due to the nonbreathing nature of the framework and an additional structural change upon cooling to cryogenic gas sorption temperature. SNU‐77H exhibits a large surface area (BET, 3670 m2 g?1), a large pore volume (1.52 cm3 g?1), and exceptionally high uptake capacities for N2, H2, O2, CO2, and CH4 gases. 相似文献
An appealing avenue for organic spintronics lies in direct coherent control of the spin population by means of pulsed electron spin resonance techniques. Whereas previous work has focused on the electrical detection of coherent spin dynamics, we demonstrate here the equivalence of an all-optical approach, allowing us to explore the influence of materials chemistry on the spin dynamics. We show that deuteration of the conjugated polymer side groups weakens the local hyperfine fields experienced by electron-hole pairs, thereby lowering the threshold for the resonant radiation intensity at which coherent coupling and spin beating occur. The technique is exquisitively sensitive to previously obscured material properties and offers a route to quantifying and tuning hyperfine fields in organic semiconductors. 相似文献