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991.
Hyzak L Moos R von Rath F Wulf V Wirtz M Melchior D Kling HW Köhler M Gäb S Schmitz OJ 《Analytical chemistry》2011,83(24):9467-9471
Matrix-assisted laser desorption ionization (MALDI) is a very powerful and widely used mass spectrometric technique to ionize high molecular weight compounds. The most commonly used dried droplet (DD) technique can lead to a concentration distribution of the analyte on the target and is therefore often not suitable for reproducible analyses. We developed a new solvent-free deposition technique, called compressed sample (CS), to prevent the distribution of the analytes caused by the crystallization of the compounds. The CS technique presented in this work allows the quantitative analysis of synthetic polymers such as derivatized maltosides with correlation coefficients of 0.999 and peptides up to 3500 Da with correlation coefficients of at least 0.982 without the use of stable-isotope-labeled standards. 相似文献
992.
Geppert M Hohnholt MC Thiel K Nürnberger S Grunwald I Rezwan K Dringen R 《Nanotechnology》2011,22(14):145101
Magnetic iron oxide nanoparticles (Fe-NP) are currently considered for various diagnostic and therapeutic applications in the brain. However, little is known on the accumulation and biocompatibility of such particles in brain cells. We have synthesized and characterized dimercaptosuccinic acid (DMSA) coated Fe-NP and have investigated their uptake by cultured brain astrocytes. DMSA-coated Fe-NP that were dispersed in physiological medium had an average hydrodynamic diameter of about 60 nm. Incubation of cultured astrocytes with these Fe-NP caused a time- and concentration-dependent accumulation of cellular iron, but did not lead within 6 h to any cell toxicity. After 4 h of incubation with 100-4000 μM iron supplied as Fe-NP, the cellular iron content reached levels between 200 and 2000 nmol mg?1 protein. The cellular iron content after exposure of astrocytes to Fe-NP at 4?°C was drastically lowered compared to cells that had been incubated at 37?°C. Electron microscopy revealed the presence of Fe-NP-containing vesicles in cells that were incubated with Fe-NP at 37?°C, but not in cells exposed to the nanoparticles at 4?°C. These data demonstrate that cultured astrocytes efficiently take up DMSA-coated Fe-NP in a process that appears to be saturable and strongly depends on the incubation temperature. 相似文献
993.
Root turnover: an important source of microbial substrates in rhizosphere remediation of recalcitrant contaminants 总被引:4,自引:0,他引:4
The growth dynamics and phenolic content of mulberry (Morus sp.) fine roots (<1 mm diameter) were determined and examined in relationship to rhizosphere remediation of recalcitrant soil contaminants. Root turnover measurements of rhizotron-grown plants showed that 58% of the fine roots produced during a 6-month growing season (June-November) died at the end of the season. The concentration of phenolic compounds in fine roots increased approximately 2-fold during the later stages of the season, and the total phenolic content of dead fine roots reached a maximum value of 38 mg/g dry weight. The late-season increase in total phenolics was primarily due to accumulation of three different flavones (morusin, morusinol, and kuwanon C). These three flavones were shown to support the growth of the bacterium Burkholderia sp. LB400, a degrader of polychlorinated biphenyls (PCBs). Thus, it has been established that, upon death, the fine roots of mulberry can serve as a source of substrate for PCB-degrading bacteria. These results establish for the first time that the chemical content and turnover rate of fine roots should be considered an important aspect of rhizosphere remediation. 相似文献
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995.
Barbara Siegmund Erich Leitner Ingo Mayer W. Pfannhauser Pavel Farkas˘ Jana Sádecká Milan Kovác 《European Food Research and Technology》1997,205(1):73-75
5,6-Dihydro-2,4,6-trimethyl-4H-1,3,5-dithiazine (thialdine) is an aroma-active compound that has been isolated from different species of meat. In this study
we have investigated the formation of thialdine using the simultaneous distillation–extraction according to Likens–Nickerson for the extraction of aroma compounds. Three isomers of thialdine were identified in the aroma extract of cooked and dried
hen meat. It was shown that these compounds are not genuine substances from the sample examined, but that they are artefacts
formed during sample preparation.
Received: 30 October 1996 相似文献
996.
997.
Organic Electronics: Charge Transport Over Multiple Length Scales in Supramolecular Fiber Transistors: Single Fiber Versus Ensemble Performance (Adv. Mater. 3/2014) 下载免费PDF全文
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