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31.
Gräter F Heider P Zangi R Berne BJ 《Journal of the American Chemical Society》2008,130(35):11578-11579
The early events in protein collapse and folding are guided by the protein's elasticity. The contributions of entropic coiling and poor solvent effects like hydrophobic forces to the elastic response of proteins are currently unknown. Using molecular simulations of stretched ubiquitin in comparison with models of proteins as entropic chains, we find a surprisingly high stiffness of the protein backbone, reflected by a persistence length of 1.2 nm, which is significantly reduced by hydrophobic forces acting between protein side chains to an apparent persistence length of 0.3-0.6 nm frequently observed in single-molecule stretching experiments. Thus, the poor solvent conditions of a protein in water lead to a protein compaction much beyond the coiling of an entropic chain and thereby allow a protein to appear softer than when using good solvents. 相似文献
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Thevis M Wilkens F Geyer H Schänzer W 《Rapid communications in mass spectrometry : RCM》2006,20(22):3393-3402
The administration of growth-promoting agents such as human growth hormone as well as compounds with respective secretagogue activity is prohibited in sports according to the regulations of the World Anti-Doping Agency. Acetylcholine esterase inhibitors have been demonstrated to stimulate growth-hormone secretion in elderly humans, and new orally active drugs have been developed to provide alternatives to therapeutic injections of growth-hormone preparations. Preventive anti-doping strategies include method development for emerging drugs and potentially misused compounds. Hence, the mass spectrometric dissociation behavior of three acetylcholine esterase inhibitors (donepezil, galantamine and rivastigmine) and a structural analogue to the growth-hormone secretagogue SM-130686 were studied using high-resolution/high-accuracy orbitrap mass spectrometry. These data provided substantial information for screening procedures, complementing common methods of sports drug testing. Using liquid-liquid extraction and subsequent liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis, the four target analytes were determined at urinary concentrations of 15-20 ng/mL, recoveries ranged from 55-97%, and assay precisions were calculated at 5.2-15.8% (intraday) and 10.2-21.6% (interday) for all compounds. The applicability of the developed assay to authentic urine specimens was tested using two administration study urine samples after application of Reminyl (galantamine) and Aricept (donepezil). In both cases, the administered drug and the respective desmethylated metabolites were detected. 相似文献
35.
Thrun F Butschke B Graening T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(16):4854-4858
Don't hold on too tightly! In a new dirhodium catalyst for C-H functionalization reactions, two tropolonato ligands are introduced as hemilabile chelating ligands (see scheme). Only two bridges hold the Rh-Rh core together. The tropolonato ligands can liberate a binding site in the equatorial coordination sphere of the catalyst. This opens a doorway to new mechanistic channels in C-H functionalization. 相似文献
36.
The nitridogallate Ca2Ga3MgN5 was obtained from reaction of the elements in sodium flux with Na‐azide at 760 °C in weld shut niobium ampoules. Crystal structure solution and refinement was carried out on the basis of single‐crystal X‐ray diffraction data. Ca2Ga3MgN5 [space group C2/m (no. 12), a = 11.160(2), b = 3.2965(7), c = 8.006(2) Å, and β = 109.93(3)°, Z = 2] shows an anionic substructure made up of mixed (Mg/Ga)N4 tetrahedra, which are sharing both common vertices and edges building a three‐dimensional network. The crystal structure of Ca2Ga3MgN5 is related to known alkaline earth nitridosilicates (MII2Si5N8, MII = Sr, Ba), but is significantly higher condensed due to additional edge‐sharing in the anionic substructure. 相似文献
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Frauke Böttcher 《Mathematische Semesterberichte》2006,53(2):245-257
Zusammenfassung Mit diesem Beitrag wird an die Gelehrte émilie du Chatelet (1706–1749) erinnert, die vor 300 Jahren in Paris geboren wurde. Der Text soll Einblicke in ihr Leben und ihren wissenschaftlichen Kontext geben.émilie du Chatelet lernte und arbeitete mathematisch, naturphilosophisch und -wissenschaftlich zu einer Zeit, als Frauen von h?herer, wissenschaftlicher Bildung institutionell augeschlossen waren und es für Frauen als unschicklich galt, die eigene Gelehrsamkeit selbstbewu?t ?ffentlich zu zeigen.Trotz dieser Hindernisse, gelang es du Chatelet sich Kenntnisse anzueignen, die die der meisten ihrer Zeitgenossen bei weitem überragten. Sie schrieb naturwissenschaftliche Abhandlungen, verfa?te ein Physiklehrbuch und fertigte in ihren letzten Lebensjahren eine kommentierte übersetzung der Principia (1686) von Newton an. Mathematics Subject Classification (2000) 01-99 相似文献
39.
Summary Large soil samples (up to 500 g) can conveniently be disintegrated by hydrogen peroxide in an utility tank under alkaline conditions to determine subsequently 129I by neutron activation analysis. Interfering elements such as Br are removed already before neutron irradiation to reduce the radiation exposure of the personnel. The precision of the method is <10% (1 RSD). The accuracy was checked by determining 129I also by the combustion method. 相似文献
40.
Frauke Sprengel 《Numerical Algorithms》2001,26(2):111-121
We propose some algorithms to solve the system of linear equations arising from the finite difference discretization on sparse grids. For this, we will use the multilevel structure of the sparse grid space or its full grid subspaces, respectively. 相似文献