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The reversible addition–fragmentation chain‐transfer (RAFT) process represents a sophisticated polymerization technique for the preparation of tailored and well‐defined polymers from acrylates, acrylamides, and (meth)acrylates. The direct switching from other methods, such as cationic polymerizations, without the need for tedious functionalization and purification steps remains challenging. Within this study, it is demonstrated that poly(2‐oxazoline) (P(Ox)) macro chain‐transfer agents (macro‐CTAs) can be prepared through the quenching of the cationic ring‐opening polymerization with a carbonotrithioate salt. The end‐functionalization of the P(Ox)s is observed to be almost quantitative and the macro‐CTAs could be directly used for RAFT polymerization without further purification. This one‐pot procedure could be extended to a variety of (multi)block copolymers consisting of different 2‐oxazolines and acrylates with good‐to‐excellent control. Kinetic studies revealed the controlled polymerization of block copolymers, which are further accessible for α‐ and ω‐end‐functionalization. The simplicity and versatility of the approach promise a straightforward access to block copolymers from cationic and controlled radical polymerizations.  相似文献   
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A liquid chromatographic/tandem mass spectrometric method was developed and validated for the quantitation of capecitabine and its metabolite 5-fluorouracil in human plasma. The simultaneous determination of both analytes was achieved by a column switching method using a trapping column and two analytical columns with different stationary phases. Isocratic elution was used for the separation of capecitabine on a C18 column whereas 5-fluorouracil was separated using gradient elution on an non-polar carbon phase. The calibration curves were linear for both compounds with a correlation factor (R2) > 0.9993 for 5-fluorouracil and >0.9942 for capecitabine. The assay was validated in the concentration range 5.00-1000 ng ml(-1) for both compounds. The intra-day precision was better than 10% for 5-fluorouracil and better than 11% for capecitabine whereas the inter-day precision was better than 8% for 5-fluorouracil and better than 14% for capecitabine.  相似文献   
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Different virtual screening techniques are available as alternatives to high throughput screening. These different techniques have been rarely used together on the same target. We had the opportunity to do so in order to discover novel blockers of the voltage-dependent potassium channel Kv1.5, a potential target for the treatment of atrial fibrillation. Our corporate database was searched, using a protein-based pharmacophore, derived from a homology model, as query. As a result, 244 molecules were screened in vitro, 19 of them (7.8%) were found to be active. Five of them, belonging to five different chemical classes, exhibited IC50 values under 10 microM. The performance of this structure-based virtual screening protocol has been compared with those of similarity and ligand-based pharmacophore searches. The analysis of the results supports the conventional wisdom of using as many virtual screening techniques as possible in order to maximize the chance of finding as many chemotypes as possible.  相似文献   
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  总被引:1,自引:0,他引:1  
Detection of autofluorescence at the skin surface is highly influenced by melanin and hemoglobin. Epidermal absorption and scattering may also be an influencing factor and is represented in this article as a quantitative parameter, epidermal thickness. To examine this parameter we measured the 370 nm fluorescence in vivo after excitation with 330 nm and the 455 nm fluorescence after excitation with 330 and 370 nm. Measurements were performed on sun-exposed skin at the dorsal aspect of the forearm and shoulder and on nonexposed buttock skin. Skin pigmentation and redness of the same body sites were measured by reflectance spectroscopy. The thickness of the stratum corneum and the cellular part of epidermis was quantified by light microscopy of skin biopsies. Multiple regression analysis was used to find correlations between autofluorescence and the potential influencing factors. We found a highly significant correlation of skin autofluorescence with pigmentation and redness for both emission wavelengths (Em). A small but significant correlation to epidermal thickness was found only for excitation wavelength (Ex) 370 nm and Em455 nm if body site was included in the analysis. No correlation between Ex330:Em370 and Ex330:Em455 and thickness of epidermis was found. For practical use, correction of skin autofluorescence for pigmentation is essential, correction for redness is of less importance and correction for epidermal thickness is unnecessary.  相似文献   
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For a long time d10‐ML2 fragments have been known for their potential to activate unreactive bonds by oxidative addition. In the development of more active species, two approaches have proven successful: the use of strong σ‐donating ligands leading to electron‐rich metal centers and the employment of chelating ligands resulting in a bent coordination geometry. Combining these two strategies, we synthesized bis‐NHC chelate complexes of nickel(0) and platinum(0). Bis(1,5‐cyclooctadiene)nickel(0) and ‐platinum(0) react with bisimidazolium salts, deprotonated in situ at room temperature, to yield tetrahedral or trigonal‐planar bis‐NHC chelate olefin complexes. The synthesis and characterization of these complexes as well as a first example of C? C bond activation with these systems are reported. Due to the enforced cis arrangement of two NHCs, these compounds should open interesting perspectives for bond‐activation chemistry and catalysis.  相似文献   
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