Solution equilibria of aromatic dinitroso compounds: a combined NMR and DFT study

Solution-state nitroso monomer-azodioxide equilibria and conformational freedom of several aromatic dinitroso derivatives, differing in the spacer group between the aromatic rings, were studied by one- and two-dimensional variable temperature ¹H NMR spectroscopy and by quantum chemical calculations. The proton signals of nitroso monomer-azodioxide mixtures revealed by low-temperature NMR were assigned and validated using B3LYP-D3/6-311+G(2d,p)/SMD level of theory. In almost all cases, a preference towards the formation of only one azodioxy isomer of aromatic dinitroso compounds was found, which was assigned to Z-dimer according to computational data. Nevertheless, the computed small energy difference between the Z- and E-isomer could not account for the extreme preference for Z-dimer formation, indicating an influence of entropic or solvent effects. The formation of shorter oligomers in solution was excluded based on integrated ¹H NMR signal intensities. The experimental results indicated an average dimerization Gibbs energy of about ??5 kJ/mol at 223 K and were found to be in very good correlation with dimerization energies obtained by solution-phase optimization.

     

Arrangements on Parametric Surfaces I: General Framework and Infrastructure

We introduce a framework for the construction, maintenance, and manipulation of arrangements of curves embedded on certain two-dimensional orientable parametric surfaces in three-dimensional space. The framework applies to planes, cylinders, spheres, tori, and surfaces homeomorphic to them. We reduce the effort needed to generalize existing algorithms, such as the sweep line and zone traversal algorithms, originally designed for arrangements of bounded curves in the plane, by extensive reuse of code. We have realized our approach as the Cgal package Arrangement_on_surface_2. We define a compact and modular interface for our framework; for a given application a required small subset of the interface can be identified. Then, only this subset must be implemented. A companion paper describes concretizations for several types of surfaces and curves embedded on them, and applications. This is the first implementation of a generic algorithm that can handle arrangements on a large class of parametric surfaces.     

Aromatic Polynitro Ether Derivatives of Cellulose

The nucleophilic reaction of sodium cellulosate in the form of membrane or cotton fabric with 2, 4-dinitrohalo-benzenes, 2, 4, 6-trinitrochlorobenzene, 2, 4, 6-trinitrobenzyl bromide, and 2, 4, 6-trinitrostyrene was investigated. The degree of substitution attained with the dinitroaryl derivatives was much higher than that with the trinitroaryl derivatives. The reaction proceeded through Meisen-heimer complexes, which in the case of the trinitro derivatives could be isolated. The ability of the polynitro phenyl ether derivatives of the cellulose to form n- and π-complexes was investigated using naphthalene and p-toluidine. No -π- complex was formed with the former, and the latter gave complexes only with the 2, 4, 6-trinitrobenzyl or -phenethyl cellulose derivatives but not with the trinitrophenyl. The results were explained as due to steric hindrance from the polymeric cellulosic backbone.     

Biologically Relevant Molecular Transducer with Increased Computing Power and Iterative Abilities

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Spin Selectivity in Electron Transfer in Photosystem I

Photosystem I (PSI) is one of the most studied electron transfer (ET) systems in nature; it is found in plants, algae, and bacteria. The effect of the system structure and its electronic properties on the electron transfer rate and yield was investigated for years in details. In this work we show that not only those system properties affect the ET efficiency, but also the electrons’ spin. Using a newly developed spintronic device and a technique which enables control over the orientation of the PSI monolayer relative to the device (silver) surface, it was possible to evaluate the degree and direction of the spin polarization in ET in PSI. We find high‐spin selectivity throughout the entire ET path and establish that the spins of the electrons being transferred are aligned parallel to their momenta. The spin selectivity peaks at 300 K and vanishes at temperatures below about 150 K. A mechanism is suggested in which the chiral structure of the protein complex plays an important role in determining the high‐spin selectivity and its temperature dependence. Our observation of high light induced spin dependent ET in PSI introduces the possibility that spin may play an important role in ET in biology.     

数字合成(上)

什么是数字合成?当我们讨论它的时候,首先我们试着把多个元素整合成一个单个的完整的整体图像,当大多数这些技术仍然适用于图像时,我们将关注有用的和合理的能处理大的图像序列的工具和方法。正如您所见的,一个技术很好的合成师是可以包括从技师到艺术家的,不只是需要基本了解“操作的工具”,这里包括多种软件,而且必须是一个能洞察视觉本质的人。记住这一点,当遇到“它看起来是否正确?”的问题时,所有技术考虑都是不重要了,很明显只是一个对主题的把握,同时一个好的合成师都应以高要求来做出每个决定。定义什么是合成?有一个基本的定义:把…     

H,C, N and S stable isotopes and mineral profiles to objectively guarantee the authenticity of grated hard cheeses

In compliance with the European law (EC No. 510/2006), geographical indications and designations of origin for agricultural products and foodstuffs must be protected against mislabelling. This is particularly important for PDO hard cheeses, as Parmigiano Reggiano, that can cost up to the double of the no-PDO competitors.     

Detection of Metal Ions (Cu2+, Hg2+) and Cocaine by Using Ligation DNAzyme Machinery

The Cu²⁺‐dependent ligation DNAzyme is implemented as a biocatalyst for the colorimetric or chemiluminescence detection of Cu²⁺ ions, Hg²⁺ ions, or cocaine. These sensing platforms are based on the structural tailoring of the sequence of the Cu²⁺‐dependent ligation DNAzyme for specific analytes. The tethering of a subunit of the hemin/G‐quadruplex DNAzyme to the ligation DNAzyme sequence, and the incorporation of an imidazole‐functionalized nucleic‐acid sequence, which acts as a co‐substrate for the ligation DNAzyme that is tethered to the complementary hemin/G‐quadruplex subunit. In the presence of different analytes, Cu²⁺ ions, Hg²⁺ ions, or cocaine, the pretailored Cu²⁺‐dependent ligation DNAzyme sequence stimulates the respective ligation process by combining the imidazole‐functionalized co‐substrate with the ligation DNAzyme sequence. These reactions lead to the self‐assembly of stable hemin/G‐quadruplex DNAzyme nanostructures that enable the colorimetric analysis of the substrate through the DNAzyme‐catalyzed oxidation of 2,2′‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonic acid), ABTS^2?, by H₂O₂ into the colored product ABTS^.?, or the chemiluminescence detection of the substrate through the DNAzyme‐catalyzed oxidation of luminol by H₂O₂. The detection limits for the sensing of Cu²⁺ ions, Hg²⁺ ions, and cocaine correspond to 1 nM , 10 nM and 2.5 μM , respectively. These different sensing platforms also reveal impressive selectivities.