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排序方式: 共有215条查询结果,搜索用时 15 毫秒
21.
Heiner Andreas P.; Berendsen Herman J.C.; van Gunsteren Wilfred F. 《Protein engineering, design & selection : PEDS》1993,6(4):397-408
In this paper we describe the achievements and pitfalls encounteredin doing structure predictions of protein mutants using moleculardynamics simulation techniques in which properties of atomsare slowly changed as a function of time. Basically the methodconsists of a thermodynamic integration (slow growth) calculationused for free energy determination, but aimed at structure prediction;this allows for a fast determination of the mutant structure.We compared the calculated structure of the mutants Met222Ala,Met222Phe and Met222Gln of subtilisin BPN' with the respectiveX-ray structures and found good agreement between predictedand X-ray structure. The conformation of the residue subjectto the mutation is relatively easy to predict and is mainlydetermined by packing criteria. When the side chain has polargroups its exact orientation may pose problems; long-range Coulombinteractions may generate a polarization feedback involvingsystem relaxation times beyond the simulation time. Changesinduced in the environment are harder to predict using thismethod. In particular, rearrangement of the hydration structurewas difficult to predict correctly, probably because of thelong relaxation times. In all conversions made the changes observedin the environment were found to be history-dependent and inparticular the hydrogen bonding patterns provided evidence formetastable substates. In all cases the structure predicted wascompared with available kinetic data and the reduced activitycould be explained in terms of changes in the configurationof the active site. 相似文献
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Increased computer speed has helped to proliferate tomography throughout the geosciences. Although best known from the medical CATscan, tomography is also a powerful tool for geological problems. Whereas qualitative tomography is widely used, quantitative data from tomograms are not so commonly available. Presented here are two programs, Electron Tomography Segmentation, surface Area, and Volume (ETSAV) and Electron Tomography CUTter (ETCut), that were written to obtain quantitative volume and surface-area data from tomograms. Based on a specified threshold value, ETSAV distinguishes objects within a tomogram and then returns volume and surface-area data for each object. If object separation is unsatisfactory using a single threshold, ETCut is called to digitally separate objects that appear connected in the tomogram, allowing ETSAV to perform its functions. By knowing the nature of the object of interest, error can be corrected to, on average, less than 5% for a single object; combined volumes of many particles of different sizes may result in lesser errors. A section of the Brenham pallasite meteorite was examined using the programs. Olivine comprises 67.2% of the volume (50.4% wt%), followed by FeNi metal at 23.1% (39.3% wt%), troilite at 4.4% (4.8% wt%), and schreibersite at 3.4% (5.5% wt%). In all, 56.1% and 44.7% of the troilite and schreibersite surface areas, respectively, border olivine, suggesting that they wet olivine. Since the programs can be applied to any tomogram, from any field, there are many potential applications. 相似文献
25.
Dipl. iur. Dipl. krim. Andrea Kemper Dr. med. Michael Kölch Prof. Heiner Fangerau Prof. Dr. med. Jörg M. Fegert 《Ethik in der Medizin》2010,22(1):33-47
Definition of the problem Medical confidentiality, which is one of the main pillars of medical ethics, has taken a decisive role in the latest discussions about the improvement of child protection laws. Inexplicit and plurivalent arrangements and procedures of how to legally handle child abuse cases when persons with legal custody refuse to take further support are seen as an obstacle for effective child protection. Arguments Non-specific legal regulations lead to task uncertainty and hesitation on the side of health care professionals, which can result in the delay or even prevention of necessary actions. Therefore, new laws on the federal level have been passed in order to establish certainty with regard to professional secrecy and in order to foster networking among the actors in the field of child protection. Conclusion The paper analyses and discusses these legal attempts at strengthening child protection. Although some of the federal laws have the potential of clarification, the great number of laws and their explication restricts their impact. 相似文献
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Heiner Fangerau 《Ethik in der Medizin》2011,18(3):87-88
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Mariya Aloshyna Begoa Milin Medina Lars Poulsen Juliette Moreau David Beljonne Jrme Cornil Giuseppe Di Silvestro Michele Cerminara Francesco Meinardi Riccardo Tubino Heiner Detert Sigurd Schrader Hans‐Joachim Egelhaaf Chiara Botta Johannes Gierschner 《Advanced functional materials》2008,18(6):915-921
Perhydrotriphenylene‐based channel‐forming inclusion compounds (ICs) and thin films made of polyphenylenevinylene (PPV)‐type oligomers with terminal alkoxy groups are investigated and compared in a combined experimental and theoretical approach. Interchromophore interactions and host‐guest interactions are elucidated by UV/Vis and Raman spectroscopy. The impact of the local environment of the chromophore on the optical and photophysical properties is discussed in light of quantum‐chemical calculations. In stark contrast to thin films where preferential side‐by‐side orientation leads to quenching of photoluminescence (PL) via non‐emissive traps, the ICs are found to be attractive materials for opto‐electronic applications: they offer high chromophore concentrations, but at the same time behave as quasi‐isolated entities of tightly packed, well‐oriented objects with high PL quantum yields and the possibility of color tuning. 相似文献
28.
Ulf Stalmach Heiner Detert Herbert Meier Volker Gebhardt Dietrich Haarer Andreas Bacher Hans-Werner Schmidt 《Optical Materials》1998,9(1-4):77-81
The preparation of LEDs with poly( p-phenylenevinylene) (PPV) as emitting material is well established. However, due to the presence of a distribution of conjugated chain lengths in the polymer, systematic investigations of the electroluminescence with polymeric materials are difficult, as far as the optical emission is concerned. We are studying the relationship between structural variation of substituted oligo(p-phenylenevinylene)s and their electroluminescent behaviour using a series of distyrylbenzenes with a variety of substituents in order to investigate their influence on the electroluminescence (EL). Furthermore, we synthesized a homologous series of monodisperse oligo(2,5-dipropoxy-1,4-phenylenevinylene)s with up to 11 repeating units. This series covers the spectrum from monomer to polymer. The influence on the EL can be investigated by preparing single layer LEDs using vapor deposition or spincoating of the oligomers in a polystyrene (PS) matrix. The comparison of photoluminescence (PL)- and EL-spectra shows that the photophysical properties of the oligomers are strongly altered by aggregation phenomena. 相似文献
29.
Andreas Mauerer Bastian Lange Goetz Hannes Welsch Frank Heidenau Werner Adler Raimund Forst Richard Heiner Richter 《Journal of materials science. Materials in medicine》2014,25(3):813-821
The aim of this study was the investigation of a copper-filled TiO2 coating, that in vitro showed good antibacterial properties combined with good tissue tolerance in an animal model. To better understand the antibacterial mechanism of the bioactive coating the release of copper (Cu) ions over time was monitored to be able to detect possible threats as well as possible fields of application. 30 New Zealand White rabbits were divided into two groups with 15 animals per group. In group 1 (control group) Ti6Al4 V bolts were implanted into the distal femur, in group 2 the Ti6Al4 V bolts were coated with four TiO2-coatings with integrated Cu2+-ions (4 × Cu–TiO2). Blood tests were performed weekly until the animals were sacrificed 4 weeks postoperative. The maximum peak of Cu and ceruloplasmin concentration could be seen in both groups one week postoperative, whereas the Cu values in group II were significantly higher. The Cu concentration in both groups approximated the initial basic values 4 weeks postoperative. The 4 × Cu–TiO2 coating tested in our rabbit model for total knee arthroplasty is an active coating that releases potentially antibacterial Cu2+ for 4 weeks with a peak 1 week postoperative. The bioactive coating could be a promising approach for a use in the field of implant related infection, orthopaedic revision and tumor surgery in the future. 相似文献
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