四氟乙烯齐聚体的反应 四氟乙烯四、五聚体和芳香胺的反应

前已报道四氟乙烯四聚体(全氟-3,4-甲基己烯-3)(1)、五聚体(全氟-3,4-二甲基-4-乙基己烯-2)(2)和脂肪烷氧以及脂肪胺的亲核反应.本文报道化合物1,2和芳香胺如苯胺、β-萘胺的反应.由于烯烃1、2双键处于分子中间,因而当亲核试剂进攻时,双键容易发生重排,生成的末端基烯烃更具反应性,故导致一取代、二取代、三取代以及环化降解等复杂产物.     

Toward amino acid typing for proteins in FFLUX

Continuing the development of the FFLUX, a multipolar polarizable force field driven by machine learning, we present a modern approach to atom‐typing and building transferable models for predicting atomic properties in proteins. Amino acid atomic charges in a peptide chain respond to the substitution of a neighboring residue and this response can be categorized in a manner similar to atom‐typing. Using a machine learning method called kriging, we are able to build predictive models for an atom that is defined, not only by its local environment, but also by its neighboring residues, for a minimal additional computational cost. We found that prediction errors were up to 11 times lower when using a model specific to the correct group of neighboring residues, with a mean prediction of ∼0.0015 au. This finding suggests that atoms in a force field should be defined by more than just their immediate atomic neighbors. When comparing an atom in a single alanine to an analogous atom in a deca‐alanine helix, the mean difference in charge is 0.026 au. Meanwhile, the same difference between a trialanine and a deca‐alanine helix is only 0.012 au. When compared to deca‐alanine models, the transferable models are up to 20 times faster to train, and require significantly less ab initio calculation, providing a practical route to modeling large biological systems. © 2016 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc.     

Spreading and retraction dynamics of smectic liquid crystal domains at interfaces

The spreading of a liquid drop over liquid subphase can be driven by change in interfacial tension mediated through a surfactant, volatile solvent or photoinduced reaction. In contrast to the spreading dynamics of a liquid drop, a liquid crystal drop with anisotropic structure can lead to interesting behaviour due to its viscoelasticity and anchoring at the interfaces. Recently, we have reported studies on unusual spreading and retraction dynamics of a smectic domain doped with a fluorescent dye in the collapsed state of a Langmuir monolayer. Under epifluorescence microscope, during excitation, a stack of layers of the dye-doped smectic domain gets sheared causing the domain to spread asymmetrically. Further, due to line tension, the domain transforms into a circular shape. We also find the domain size to be about twice that of the initial size. Interestingly, in the absence of excitation, the domain retracts to a smaller area. During retraction of the domain, successive generation of edge dislocation loops arising from a nucleus results in an increase in the domain thickness. The dynamics of spreading and retraction of the domain can be understood by invoking changes in the spreading coefficient due to photoinduced modification of the interfacial tension.     

Superiority of a new gradient system utilizing a critical threshold for the adsorption capacity of polypeptides to column packing when compared with a standard gradient system for the simultaneous and quantitative analysis of polypeptides

Compared with a standard gradient system, the new gradient system which we developed has a major advantage because it permits a wide range of acetonitrile content, e.g. more than the critical threshold, in the polypeptide solution and allows the quantitative analysis of the polypeptide with satisfactory analytical precision. Additionally, this new gradient system allows the enhancement of the sensitivity of the polypeptide analysis proportionate to the increased volume of solution loaded with the same levels of precision. In contrast, when using a standard gradient system it is difficult to analyze a polypeptide quantitatively with good precision due to either adsorption to various materials or to irregular change in the ratio between a retained and a passed peak of the polypeptide. Additionally, the appearance of a passed peak results in a loss in the sensitivity of the polypeptide analysis, although no adsorption of a polypeptide to various materials occurs in a solution with acetonitrile content more than the critical threshold. Consequently, the new gradient system is effective for the simultaneous and quantitative analysis of different polypeptides with good precision and without any loss of sensitivity due to either adsorption to various materials or the appearance of a passed peak.     

Analysis of genome sequences for genes of cyanophycin metabolism: identifying putative cyanophycin metabolizing prokaryotes

CGP, a copolymer of aspartate and arginine, serves as a storage compound for nitrogen, carbon and energy in many cyanobacteria. Analysis of available genome sequences from prokaryotes identified ORFs putatively encoding proteins of high similarity to known cyanophycin synthetases and cyanophycinases from cyanobacteria in various strains of bacteria belonging to different phylogenetic taxa and not closely related to cyanobacteria. Genes of CGP metabolism occur in a wide range of bacteria exhibiting diverse metabolic capabilities, including aerobic and anaerobic respiration, fermentation, phototrophy and chemolithoautotrophy. This study identified different groups of cyanophycin synthetases and cyanophycinases, respectively, and proposes a collective terminology for the putative genes and enzymes of cyanophycin metabolism. Among 570 different microbial strains, whose genomes have been partially or completely sequenced and are publicly accessible, we identified 44 prokaryotes which possess a cyanophycin synthetase and are putatively able to synthesize CGP. From these, 31 prokaryotes harbor also a cyanophycinase enabling them to degrade CGP to dipeptides. From the latter, 24 strains possess in addition a dipeptidase necessary to hydrolyze beta-Asp-Arg dipeptides, thereby enabling them to completely utilize CGP. Therefore, CGP seems to have a much wider distribution among prokaryotes than previously recognized. Genes putatively encoding cyanophycin synthetase homologues were not identified in the genomes of Eukarya and Archaea and are therefore obviously only occurring in Eubacteria. In addition, the outcome of this detailed in silico analysis proposes to distinguish 10 different groups of cyanophycin synthetases.     

Global approach for the selection of high temperature comprehensive two-dimensional gas chromatography experimental conditions and quantitative analysis in regards to sulfur-containing compounds in heavy petroleum cuts

Extending the knowledge on sulfur-containing compounds is crucial for the petroleum industry because they contribute to atmospheric pollution by combustion. Most of them are concentrated in heavy petroleum cuts, such as vacuum gas oils (VGOs). However, the resolution of the existing analytical methods does not allow a quantitative speciation of S-compounds contained in VGOs. Therefore, a high temperature GC×GC chromatograph hyphenated to a SCD was implemented in this study to obtain a quantitative S-compounds speciation. Firstly, various thermally stable stationary phases, in particular the new ionic liquid IL59 and Mega Wax-HT, were investigated in 1D-GC as a way to reduce the number of columns sets to be used in GC×GC. Consequently, several normal and reversed configurations of these columns were selected and tested in GC×GC. Then, a decision method was applied to facilitate the choice of the best combination of columns. Finally, the most adapted methods led to an innovative group type quantification and to a quantitative distribution of heavy sulfur species contained in a VGO sample. These results represent a major step towards the study of S-compounds in heavy petroleum cuts.     

Monitoring and classification of wastewater quality using supervised pattern recognition techniques and deterministic resolution of molecular absorption spectra based on multiwavelength UV spectra deconvolution

A field flow approach for the in situ monitoring of wastewater quality is developed and assessed in this work, based on a combination of methods employing deconvolution of molecular absorption spectra and in situ/on-line analysis of wastewater effluent of various origin. The approach involves in situ immersion probes to monitor basic physicochemical parameters followed by UV spectrum deconvolution in order to provide a rapid estimate of organic matter, suspended solids and nitrate and on-line analysis of phosphates in a fully automated setup. The collected data are then treated with a series of supervised pattern recognition techniques in order to classify wastewater effluent according to their origin in three major categories namely municipal, industrial and hospital. The results suggest that the method affords a good approximation of realistic concentrations, as determined by reference methods, while it affords a good classification among various wastewater effluents of different origin. In that manner, the method enables a rapid inference of treated wastewater quality and a robust assessment of treatment process state, especially with regards to violations of effluent quality parameters.     

Hydrogen-bonding cooperativity: using an intramolecular hydrogen bond to design a carbohydrate derivative with a cooperative hydrogen-bond donor centre

Neighbouring groups can be strategically located to polarise HO.OH intramolecular hydrogen bonds in an intended direction. A group with a unique hydrogen-bond donor or acceptor character, located at hydrogen-bonding distance to a particular OH group, has been used to initiate the hydrogen-bond network and to polarise a HO.OH hydrogen bond in a predicted direction. This enhanced the donor character of a particular OH group and made it a cooperative hydrogen-bond centre. We have proved that a five-membered-ring intramolecular hydrogen bond established between an amide NH group and a hydroxy group (1,2-e,a), which is additionally located in a 1,3-cis-diaxial relationship to a second hydroxy group, can be used to select a unique direction on the six-membered-ring intramolecular hydrogen bond between the two axial OH groups, so that one of them behaves as an efficient cooperative donor. Talose derivative 3 was designed and synthesised to prove this hydrogen-bonding network by NMR spectroscopy, and the mannopyranoside derivatives 1 and 2 were used as models to demonstrate the presence in solution of the 1,2-(e,a)/five-membered-ring intramolecular hydrogen bond. Once a well-defined hydrogen-bond is formed between the OH and the amido groups of a pyranose ring, these hydrogen-bonding groups no longer act as independent hydrogen-bonding centres, but as hydrogen-bonding arrays. This introduces a new perspective on the properties of carbohydrate OH groups and it is important for the de novo design of molecular recognition processes, at least in nonpolar media. Carbohydrates 1-3 have shown to be efficient phosphate binders in nonpolar solvents owing to the presence of cooperative hydroxy centres in the molecule.     

Experimental study of dielectrophoresis and liquid dielectrophoresis mechanisms for particle capture in a droplet

This work presents a microfluidic system that can transport, concentrate, and capture particles in a controllable droplet. Dielectrophoresis (DEP), a phenomenon in which a force is exerted on a dielectric particle when it is subjected to a non-uniform electric field, is used to manipulate particles. Liquid dielectrophoresis (LDEP), a phenomenon in which a liquid moves toward regions of high electric field strength under a non-uniform electric field, is used to manipulate the fluid. In this study, a mechanism of droplet creation presented in a previous work that uses DEP and LDEP is improved. A driving electrode with a DEP gap is used to prevent beads from getting stuck at the interface between air and liquid, which is actuated with an AC signal of 200 V(pp) at a frequency of 100 kHz. DEP theory is used to calculate the DEP force in the liquid, and LDEP theory is used to analyze the influence of the DEP gap. The increment of the actuation voltage due to the electrode with a DEP gap is calculated. A set of microwell electrodes is used to capture a bead using DEP force, which is actuated with an AC signal of 20 V(pp) at a frequency of 5 MHz. A simulation is carried out to investigate the dimensions of the DEP gap and microwell electrodes. Experiments are performed to demonstrate the creation of a 100-nL droplet and the capture of individual 10-μm polystyrene latex beads in the droplet.     

Palladium‐Assisted Cleavage of Peptides and Proteins Containing a Backbone with Thiazolidine Linkage

The design and synthesis of biomolecules that are responsive to external stimuli is of great interest in various research areas, such as in the preparation of smart biomaterial and chemical biology. Polypeptide backbone disassembly as a response to a particular stimulus is of interest, as it leads to a complete loss of the protein tertiary structure and, as a result, to a loss of function. In this study, a strategy based on palladium‐assisted efficient cleavage of backbone thiazolidine linkage in peptides and proteins was developed. Using a fluorescence‐based assay, encompassing ubiquitinated peptide with a quenching florescence pair, it was possible to optimize the cleavage step after rapid screening of various conditions, such as the type of metal complexes and reaction additives. The optimized conditions prompted fast cleavage of the thiazolidine linkage. The straightforward introduction of a backbone thiazolidine linkage in peptide and proteins coupled with the chemical methods used offers new opportunities in controlling macromolecule function and might, with the aid of cellular protein delivery methods, be applied in cellular settings.     

Cooperative Chemotaxis of Magnesium Microswimmers for Corrosion Spotting

Numerous artificial micro- and nanomotors, as well as various swimmers have been inspired by living organisms that are able to move in a coordinated manner. Their cooperation has also gained a lot of attention because the resulting clusters are able to adapt to changes in their environment and to perform complex tasks. However, mimicking such a collective behavior remains a challenge. In the present work, magnesium microparticles are used as chemotactic swimmers with pronounced collective features, allowing the gradual formation of macroscopic agglomerates. The formed clusters act like a single swimmer able to follow pH gradients. This dynamic behavior can be used to spot localized corrosion events in a straightforward way. The autonomous docking of the swimmers to the corrosion site leads to the formation of a local protection layer, thus increasing corrosion resistance and triggering partial self-healing.     

Applications of rule-induction in the derivation of quantitative structure-activity relationships

Summary Recently, methods have been developed in the field of Artificial Intelligence (AI), specifically in the expert systems area using rule-induction, designed to extract rules from data. We have applied these methods to the analysis of molecular series with the objective of generating rules which are predictive and reliable.The input to rule-induction consists of a number of examples with known outcomes (a training set) and the output is a tree-structured series of rules. Unlike most other analysis methods, the results of the analysis are in the form of simple statements which can be easily interpreted. These are readily applied to new data giving both a classification and a probability of correctness.Rule-induction has been applied to in-house generated and published QSAR datasets and the methodology, application and results of these analyses are discussed.The results imply that in some cases it would be advantageous to use rule-induction as a complementary technique in addition to conventional statistical and pattern-recognition methods.     

Excited-State Intramolecular Proton Transfer Dyes with Dual-State Emission Properties: Concept,Examples and Applications

Dual-state emissive (DSE) fluorophores are organic dyes displaying fluorescence emission both in dilute and concentrated solution and in the solid-state, as amorphous, single crystal, polycrystalline samples or thin films. This comes in contrast to the vast majority of organic fluorescent dyes which typically show intense fluorescence in solution but are quenched in concentrated media and in the solid-state owing to π-stacking interactions; a well-known phenomenon called aggregation-caused quenching (ACQ). On the contrary, molecular rotors with a significant number of free rotations have been engineered to show quenched emission in solution but strong fluorescence in the aggregated-state thanks to restriction of the intramolecular motions. This is the concept of aggregation-induced emission (AIE). DSE fluorophores have been far less explored despite the fact that they are at the crossroad of ACQ and AIE phenomena and allow targeting applications both in solution (bio-conjugation, sensing, imaging) and solid-state (organic electronics, data encryption, lasing, luminescent displays). Excited-State Intramolecular Proton Transfer (ESIPT) fluorescence is particularly suitable to engineer DSE dyes. Indeed, ESIPT fluorescence, which relies on a phototautomerism between normal and tautomeric species, is characterized by a strong emission in the solid-state along with a large Stokes’ shift, an enhanced photostability and a strong sensitivity to the close environment, a feature prone to be used in bio-sensing. A drawback that needs to be overcome is their weak emission intensity in solution, owing to detrimental molecular motions in the excited-state. Several strategies have been proposed in that regard. In the past few years, a growing number of examples of DSE-ESIPT dyes have indeed emerged in the literature, enriching the database of such attractive dyes. This review aims at a brief but concise overview on the exploitation of ESIPT luminescence for the optimization of DSE dyes properties. In that perspective, a synergistic approach between organic synthesis, fluorescence spectroscopy and ab initio calculations has proven to be an efficient tool for the construction and optimization of DSE-ESIPT fluorophores.     

Long-lived charge-transfer states in compact donor-acceptor dyads.

Photoinduced electron transfer is a widely applied method to convert photon energy into a useful (electro)chemical potential, both in nature and in artificial devices. There is a continuing effort to develop molecular systems in which the charge-transfer state, populated by photoinduced electron transfer, survives sufficiently long to tap the energy stored in it. In general this has been found to require the construction of rather complex molecular systems, but more recently a few approaches have been reported that allow the use of much more simple and relatively small electron donor-acceptor dyads for this purpose. The most successful examples of such systems seem to be those that apply "electron spin control" to slow down the spontaneous decay of the charge-transfer state, and these are reviewed in this minireview, with a discussion of the underlying principles and a critical evaluation of some of the claims made with regard to using a pronounced "inverted-region effect" as an alternative method to prolong the lifetime of charge-transfer states.     

Borylated 2,3,4,5-Tetrachlorophthalimide and Their 2,3,4,5-Tetrachlorobenzamide Analogues: Synthesis,Their Glycosidase Inhibition and Anticancer Properties in View to Boron Neutron Capture Therapy

Tetrachlorinated phthalimide analogues bearing a boron-pinacolate ester group were synthesised via two synthetic routes and evaluated in their glycosidase modulating and anticancer properties, with a view to use them in boron neutron capture therapy (BNCT), a promising radiation type for cancer, as this therapy does little damage to biological tissue. An unexpected decarbonylation/decarboxylation to five 2,3,4,5-tetrachlorobenzamides was observed and confirmed by X-ray crystallography studies, thus, giving access to a family of borylated 2,3,4,5-tetrachlorobenzamides. Biological evaluation showed the benzamide drugs to possess good to weak potencies (74.7–870 μM) in the inhibition of glycosidases, and to have good to moderate selectivity in the inhibition of a panel of 18 glycosidases. Furthermore, in the inhibition of selected glycosidases, there is a core subset of three animal glycosidases, which is always inhibited (rat intestinal maltase α-glucosidase, bovine liver β-glucosidase and β-galactosidase). This could indicate the involvement of the boron atom in the binding. These glycosidases are targeted for the management of diabetes, viral infections (via a broad-spectrum approach) and lysosomal storage disorders. Assays against cancer cell lines revealed potency in growth inhibition for three molecules, and selectivity for one of these molecules, with the growth of the normal cell line MCF10A not being affected by this compound. One of these molecules showed both potency and selectivity; thus, it is a candidate for further study in this area. This paper provides numerous novel aspects, including expedited access to borylated 2,3,4,5-tetrachlorophthalimides and to 2,3,4,5-tetrachlorobenzamides. The latter constitutes a novel family of glycosidase modulating drugs. Furthermore, a greener synthetic access to such structures is described.     

Application of Capillary Electromigration Methods in the Analysis of Textile Dyes—Review

Fiber traces are one of (micro)traces that can be found at a crime scene. They are easily transferable and, like other forms of evidence, can provide a link between a suspect and a victim. The main purpose of this review is to present methods developed to examine textile dyes extracted for forensic purposes using different capillary electromigration methods (CEMs). Scientific papers, mainly from the 20th century, provide reliable methods for the separation of water-soluble dyes. However, dyes insoluble in aqueous solutions have been and still are a challenge. Another problem is the sensitivity of the developed methods, which is, in most cases, insufficient for forensic examination of dyes extracted from a single fiber preserved at the crime scene. Although the methodologies already developed and presented in this review have the potential to be applied in a comparative analysis of textile dye traces, there seems to be a lot of work to be conducted. Some ideas on how to resolve these problems are presented and discussed in the article.     

A fresh view on phoresis and self-phoresis

Phoresis, a classic example of particle transport driven by thermodynamic gradients, is enjoying a resurgent research interest motivated both by technological developments and by its relevance to the motility of chemically active particles. Here we succinctly review, using the case of chemophoresis (also called diffusiophoresis), the general framework of phoresis and self-phoresis formulated as a Stokes-flow problem for a liquid solution (solvent and solute) maintained out of thermodynamic equilibrium by solute gradients. Within the constraints of local equilibrium, we discuss the simplest extension of the theory in order to account for correlations in the fluid. We show that this leads to a shift from the paradigm based on the ideal case, in that self-phoresis can no longer be represented as phoresis in a self-generated composition gradient. Our review concludes with a concise overview of a few directions which we think hold the potential to reveal a rich behavior in future investigations.     

Molecular signal suppression by in situ microextraction in nuclear magnetic resonance spectroscopy

The detailed characterization of complex mixtures by NMR is often hampered by the presence of signals from uninformative compounds, the resonances of which overlap with those of the molecules of interest. We provide here a proof of principle for an approach to NMR signal suppression in complex samples using Molecularly Imprinted Polymers (MIPS). Addition of a few milligrams of polymer to a solution traps the target molecule in typical micromolar to millimolar concentration, thus achieving in situ signal suppression, without altering any other spectral features. This method minimized any manipulation or perturbation of the spectrum and was applied to a complex mixture of known compounds and to a plant extract, in both cases spiked with a compound (bisphenol A), which was subsequently removed by selective binding to a complementary MIP. What is described in this report is comparable with microextraction and may in due course be applied to a large number of analytical challenges. Copyright © 2014 John Wiley & Sons, Ltd.