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Claudia Poloni Marc C. A. Stuart Pieter van der Meulen Wiktor Szymanski Ben L. Feringa 《Chemical science》2015,6(12):7311-7318
The external photocontrol over peptide folding, by the incorporation of molecular photoswitches into their structure, provides a powerful tool to study biological processes. However, it is limited so far to switches that exhibit only a rather limited geometrical change upon photoisomerization and that show thermal instability of the photoisomer. Here we describe the use of an overcrowded alkene photoswitch to control a model β-hairpin peptide. This photoresponsive unit undergoes a large conformational change and has two thermally stable isomers which has major influence on the secondary structure and the aggregation of the peptide, permitting the phototriggered formation of amyloid-like fibrils. 相似文献
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Jan E. Almlöf P. Ulf Isacsson P. Johan Mjöberg Wiktor M. Ralowski 《Chemical physics letters》1974,26(2):215-217
Minimal basis set ab initio SCF LCAO MO calculations with gaussian-type have been performed for different conformations of the styrene molecule. The computations show the molecule to be planar and the rotational barrier of the vinyl group is estimated to 3.9 kcal/mole. 相似文献
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Wiktor Wawrzyczek Andrzej Benedict und Ryszard Jagosz 《Fresenius' Journal of Analytical Chemistry》1965,214(4):258-261
Zusammenfassung Eine schnelle und zuverlässige, potentiometrische Titrationsmethode zur Bestimmung von Erbium mit Ammoniumoxalatlösung in wäßrig-acetonischem Medium im Verhältnis 11 wurde ausgearbeitet. Man titriert in dem System Pt | ErCl3 | Hg2Cl2 + KCl | Hg. Der Potentialsprung im Äquivalenzsättigungspunkt ist bereits auf Zugabe eines Tropfens Reagenslösung sehr deutlich. Der Meßfehler überschreitet nicht die Grenzen ±0,5%.Die Methode ist bei Metallionen, die mit Ammoniumoxalat schwerlösliche Niederschläge bilden, nicht anwendbar.
Summary A rapid and accurate method for the potentiometric titration of erbium by means of ammonium oxalate solution in a water-acetone medium (11) has been worked out. The system Pt | ErCl3 | Hg2Cl2 + KCl | Hg was used. The potential jump at the neutral point is distinct, even if only one drop of the reagent is added. The error of the measurement is not greater than ±0,5%- Metal ions forming insoluble precipitates with ammonium oxalate interfere with this method.相似文献
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Wiktor Szczyrba 《Communications in Mathematical Physics》1978,60(3):215-232
Canonical variables for the generalized (non-metric) Einstein-Cartan theory of gravity are defined. The space of solutions is equipped with a closed differential 2-form . The symplectic 2-form has a diagonal representation in terms of canonical variables. A geometric interpretation of the canonical variables is presented and the 3+1 formulation of the field equations is given. 相似文献
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Over the last years, scientific interest in noncovalent interactions based on the presence of electron-depleted regions called σ-holes or π-holes has markedly accelerated. Their high directionality and strength, comparable to hydrogen bonds, has been documented in many fields of modern chemistry. The current review gathers and digests recent results concerning these bonds, with a focus on those systems where both σ and π-holes are present on the same molecule. The underlying principles guiding the bonding in both sorts of interactions are discussed, and the trends that emerge from recent work offer a guide as to how one might design systems that allow multiple noncovalent bonds to occur simultaneously, or that prefer one bond type over another. 相似文献
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Light‐Controlled Histone Deacetylase (HDAC) Inhibitors: Towards Photopharmacological Chemotherapy 下载免费PDF全文
Dr. Wiktor Szymanski Maria E. Ourailidou Dr. Willem A. Velema Prof. Dr. Frank J. Dekker Prof. Dr. Ben L. Feringa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(46):16517-16524
Cancer treatment suffers from limitations that have a major impact on the patient’s quality of life and survival. In the case of chemotherapy, the systemic distribution of cytotoxic drugs reduces their efficacy and causes severe side effects due to nonselective toxicity. Photopharmacology allows a novel approach to address these problems because it employs external, local activation of chemotherapeutic agents by using light. The development of photoswitchable histone deacetylase (HDAC) inhibitors as potential antitumor agents is reported herein. Analogues of the clinically used chemotherapeutic agents vorinostat, panobinostat, and belinostat were designed with a photoswitchable azobenzene moiety incorporated into their structure. The most promising compound exhibits high inhibitory potency in the thermodynamically less stable cis form and a significantly lower activity for the trans form, both in terms of HDAC activity and proliferation of HeLa cells. This approach offers a clear prospect towards local photoactivation of HDAC inhibition to avoid severe side effects in chemotherapy. 相似文献