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Julia Ertl Dr. Maria Elena Ortiz-Soto Thien Anh Le Julian Bechold Junwen Shan Dr. Jörg Teßmar Prof. Bernd Engels Prof. Jürgen Seibel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(26):6533-6541
Selective chemical modification of proteins plays a pivotal role for the rational design of enzymes with novel and specific functionalities. In this study, a strategic combination of genetic and chemical engineering paves the way for systematic construction of biocatalysts by tuning the product spectrum of a levansucrase from Bacillus megaterium (Bm-LS), which typically produces small levan-like oligosaccharides. The implementation of site-directed mutagenesis followed by a tyrosine-specific modification enabled control of the product synthesis: depending on the position, the modification provoked either enrichment of short oligosaccharides (up to 800 % in some cases) or triggered the formation of high molecular weight polymer. The chemical modification can recover polymerization ability in variants with defective oligosaccharide binding motifs. Molecular dynamic (MD) simulations provided insights into the effect of modifying non-native tyrosine residues on product specificity. 相似文献
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Melanie Schmidlehner Felix Faschinger Lorenz Michael Reith Martin Ertl Wolfgang Schoefberger 《应用有机金属化学》2013,27(7):395-405
In this study, novel water‐soluble corrole amino acid conjugates were synthesized and characterized. The coupling reaction of A2B‐ and A3‐corroles with glycine ethyl ester and taurine under strong basic conditions proved to be successful and yielded di‐ and trifunctionalized corrole amino acid conjugates in good yields. The subsequent metalation of the corrole/amino acid conjugates broadens the scope for applications considerably. As examples, we herein show the catalytic activity of the Mn(III) A3‐corrole towards O2 evolution. First we employed tert‐butyl hydroperoxide (t‐BuOOH) as oxidant to obtain the Mn(V)oxo species and tetrabutyl ammonium hydroxide (TBAH) as hydroxide donor agent. Furthermore, the binding properties of the non‐metalated and the Mn(III) A3‐corrole/amino sulfonic acid conjugates and transport of proteins were investigated and the conjugates exhibited binding to human serum albumin (HSA). Finally, a novel Ga(III) A3‐corrole/amino sulfonic acid derivative was synthesized and we briefly describe the photophysical properties of this compound. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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Nach Erläuterung der Modulationsüvbertragugsfunktion, einer wichtigen Kenngröβe eines szintigraphischen. Der Übertragungssystems, wird mit ihrer Hilfe ds Auflösungsvermögen von 3″ - und 5″ -Kollimator-Detektor-Systemen verglichen. Die Übertragungsfunktionen werden aus Linienverbreiterungsfunktionen ermittelt. Es wird der Verlauf der Modulationsübertragungs funktionen einzelner Kollimatoren der 3″ - und 5″-Systeme in Abhängigkeit vom Quellen-Kollimator-Abstand diskutiert. Ferner wird die λ/2-Regel benutzt, um Aussagen über die darstellbaren Detailgröβen zu machen, und schlieβlich wird die äquivalente Bandbreite für die einzelnen Modulationsübertragungsfunktionen angegeben. 相似文献
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Bădescu SC Salo P Ala-Nissila T Ying SC Jacobi K Wang Y Bedürftig K Ertl G 《Physical review letters》2002,88(13):136101
We present a combination of theoretical calculations and experiments for the low-lying vibrational excitations of H and D atoms adsorbed on the Pt(111) surface. The vibrational band states are calculated based on the full three-dimensional adiabatic potential energy surface obtained from first-principles calculations. For coverages less than three quarters of a monolayer, the observed experimental high-resolution electron peaks at 31 and 68 meV are in excellent agreement with the theoretical transitions between selected bands. Our results convincingly demonstrate the need to go beyond the local harmonic oscillator picture to understand the dynamics of this system. 相似文献
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Tip-enhanced Raman spectroscopy (TERS) is based on the optical excitation of localized surface plasmons in the tip-substrate cavity, which provides a large but local field enhancement near the tip apex. We report on TERS with smooth single crystalline surfaces as substrates. The adsorbates were CN- ions at Au(111) and malachite green isothiocyanate (MGITC) molecules at Au(111) and Pt(110) using either Au or Ir tips. The data analysis yields Raman enhancements of about 4 x 10(5) for CN- and up to 10(6) for MGITC at Au(111) with a Au tip, probing an area of less than 100 nm radius. 相似文献
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