The multi-step phosphorelay mechanism of unorthodox two-component systems in E. coli realizes ultrasensitivity to stimuli while maintaining robustness to noises

E. coli has two-component systems composed of histidine kinase proteins and response regulator proteins. For a given extracellular stimulus, a histidine kinase senses the stimulus, autophosphorylates and then passes the phosphates to the cognate response regulators. The histidine kinase in an orthodox two-component system has only one histidine domain where the autophosphorylation occurs, but a histidine kinase in some unusual two-component systems (unorthodox two-component systems) has two histidine domains and one aspartate domain. So, the unorthodox two-component systems have more complex phosphorelay mechanisms than orthodox two-component systems. In general, the two-component systems are required to promptly respond to external stimuli for survival of E. coli. In this respect, the complex multi-step phosphorelay mechanism seems to be disadvantageous, but there are several unorthodox two-component systems in E. coli. In this paper, we investigate the reason why such unorthodox two-component systems are present in E. coli. For this purpose, we have developed simplified mathematical models of both orthodox and unorthodox two-component systems and analyzed their dynamical characteristics through extensive computer simulations. We have finally revealed that the unorthodox two-component systems realize ultrasensitive responses to external stimuli and also more robust responses to noises than the orthodox two-component systems.     

Dynamic Responsive Systems for Catalytic Function

Responsive systems have recently gained much interest in the scientific community in attempts to mimic dynamic functions in biological systems. One of the fascinating potential applications of responsive systems lies in catalysis. Inspired by nature, novel responsive catalytic systems have been built that show analogy with allosteric regulation of enzymes. The design of responsive catalytic systems allows control of catalytic activity and selectivity. In this Review, advances in the field over the last four decades are discussed and a comparison is made amongst the dynamic responsive systems based on the principles underlying their catalytic mechanisms. The catalyst systems are sorted according to the triggers used to achieve control of the catalytic activity and the distinct catalytic reactions illustrated.     

Structural evolution in binary halide systems with cations in the oxidation state +1

We analyze the structural evolution of binary halide systems with a common anion and cations in the oxidation state +1. For eutectic-type liquid-solid diagrams and in diagrams containing incomplete solid solutions or solid solutions with a liquidus minimum, absolute and relative deflections of the experimental liquidus curve from the ideal curve were determined. The major factors are recognized influencing the structural evolution from systems containing solid solutions to eutectic systems with a positive deflection of the experimental liquidus from the ideal curve and then to ideal eutectic systems, as well as from ideal eutectic systems to eutectic systems with a negative deflection of the experimental liquidus from the ideal curve and then to systems containing compounds.     

Small-angle neutron scattering studies of dynamics and hierarchical pattern formation in binary mixtures of polymers and small molecules

We present the dynamics of the composition fluctuations and pattern formation of two-component systems in both single-phase and two-phase states as studied by time-resolved small-angle neutron scattering and light scattering. Two-component systems to be covered here include not only dynamically symmetric systems, in which each component has nearly identical self-diffusion coefficients, but also dynamically asymmetric systems, in which each component has different self-diffusion coefficients. We compare the dynamic behaviors of the two systems and illuminate their important differences. The scattering studies presented for dynamically asymmetric systems highlight that stress–diffusion coupling and viscoelastic effects strongly affect the dynamics and pattern formation. For dynamically symmetric systems, we examine the universality existing in both polymer systems and small-molecule systems as well as new features concerning the time evolution of hierarchical structures during phase separation via spinodal decomposition over a wide range of wave numbers (up to four orders of magnitude). For both systems, we emphasize that polymers provide good model systems for studying the dynamics and pattern formation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3027–3062, 2004     

Molecular and Supramolecular Multiredox Systems

The design and synthesis of molecular and supramolecular multiredox systems have been summarized. These systems are of great importance as they can be employed in the next generation of materials for energy storage, energy transport, and solar fuel production. Nature provides guiding pathways and insights to judiciously incorporate and tune the various molecular and supramolecular design aspects that result in the formation of complex and efficient systems. In this review, we have classified molecular multiredox systems into organic and organic-inorganic hybrid systems. The organic multiredox systems are further classified into multielectron acceptors, multielectron donors and ambipolar molecules. Synthetic chemists have integrated different electron donating and electron withdrawing groups to realize these complex molecular systems. Further, we have reviewed supramolecular multiredox systems, redox-active host-guest recognition, including mechanically interlocked systems. Finally, the review provides a discussion on the diverse applications, e. g. in artificial photosynthesis, water splitting, dynamic random access memory, etc. that can be realized from these artificial molecular or supramolecular multiredox systems.     

Multiple hyphenation of liquid chromatography with nuclear magnetic resonance spectroscopy, mass spectrometry and beyond

The advent of sensitive and reliable HPLC-NMR and HPLC-MS systems has revolutionised the identification of compounds eluting from chromatographic systems. More recently systems have been described wherein both NMR and MS are used together to provide an immensely powerful means of characterising compounds in chromatographic eluents. Here the construction and application of combined HPLC-NMR-MS systems to the analysis of mixtures of pharmaceuticals, drug metabolites in biological fluids and natural products in plant extracts is reviewed. In addition preliminary work with alternative systems such as HPLC-UV-NMR-FTIR-MS is highlighted and the prospects for such complex systems considered.     

Time-based flow injection analysis

Time-based flow-injection systems are novel measurement systems which use induced dispersion of the sample in the system and measurement of time to evaluate the concentration of the analyte in the sample. There are two types of time-based system. In the standard systems, assays are based on the chemistries of the classical intensity assays; in the pseudo-titration systems, the assays are based on classical titration chemistries. These systems are discussed in terms of basic theory, classification of the systems and their advantages.     

Expert systems for method development and validation in HPLC

ESCA, Expert Systems Applied to Chemical Analysis, started its research in March 1987, with the aim of building prototype expert systems for HPLC method development. Results of this research have been published as the work has progressed. The project is now completed and this paper summarises some of the overall project conclusions. Seven different expert systems have been built which tackle problems throughout the process of method development, four stand-alone systems and three integrated systems. The object of ESCA was to evaluate the applicability of expert system technology to analytical chemistry and not all the systems were built for commercial uses. Many of the systems tackle problems specific to one or more of the partners and thus may not be useful outside this environment. However, the results of the work are still pertinent to analysts wishing to build their own systems. These results are described, however, the emphasis of the paper is on those systems developed for method validation.Method validation for HPLC is a complex task which requires many characteristics of the method to be tested, e.g. accuracy, precision, etc. The expert systems built within ESCA concern the validation of precision. Two systems were developed for repeatability testing and ruggedness testing. The method validation process can be divided into several discrete stages, these include: (1) The selection of the method feature to test, for instance which factors can influence the ruggedness of a method. (2) The definition of a test procedure, for instance an efficient statistical design. (3) The execution of experiments and the interpretation of results. (4) A diagnosis of any observed problem. This paper describes these two systems in some detail and summarises some of the results obtained from their evaluation. It concludes that expert systems can be useful in solving analytical problems and the integration of several expert systems can provide extremely powerful tools for the analyst.     

Flow injection on-line electrothermal atomic absorption spectrometry

Today the greatest hindrances to couple the continuous FI system to discrete ETAAS operations have been overcome as demonstrated by the great number of papers published in the last few years. This paper reviews 109 references to the development and expansion of the FI-ETAAS methodology. The selected FI-ETAAS systems, namely: on-line column preconcentration and separation systems; on-line knotted reactor preconcentration systems; on-line aerosol deposition systems; flow-injection for in situ trapping of volatile compounds and miscellaneous on-line systems.     

Solvents showing the external heavy atom effect in phosphorimetry

Ten solvents containing heavy atoms were examined for suitability for use in the external heavy atom effect for routine phosphorimetry. In previous work only iodine-containing solvent systems have been used, and the incongruity of enhancement results for structurally similar compounds suggests that the ultraviolet transmission characteristics of the solvent systems may be responsible for fractional enhancements. In this study the effect of chlorine-, bromine-, and iodine-containing solvent systems on phosphorescence and fluorescence intensities was investigated. Generally, chlorine-, and bromine-containing solvent systems showed a significant improvement in phosphorimetric enhancements with slightly longer lifetimes than in solvent systems containing iodine. As expected from their smaller spin-orbit coupling, chlorine-containing solvent systems yield smaller enhancements than bromine-containing solvent systems. Solvent systems containing bromine seem to offer the best compromise between ultraviolet transmission characteristics and large spin-orbit coupling constants.     

Automatic deductive systems for chemistry

Deductive systems are general programs intended to assist in the design of experiments and in data processing. In such systems no mathematical assumptions are made; only the fundamental law of conservation of energy/mass is used; and the systems have a predictive capability that does not use “state-of-the-art libraries”. Two kinds of deductive systems are available: numeric deductive systems which have computative as well as predictive capabilities, and alphanumeric deductive systems which have only predictive capabilities and can be used to predict possible reaction paths. The current status of both kinds is reviewed, and examples of the use of a fully operational numerical deductive system are discussed.     

On the geometry of chemical reaction and phase equilibria

Kuhn-Tucker optimization theory is employed to obtain new results for the problem of the determination of equilibria in multi-phase multi-reaction systems. The results provide a complete classification of the possible types of behaviour that can occur for such systems. In this classification, there is an essential difference between the cases of systems for which no reactions have a set of stoichiometric coefficients that sum algebraically to zero, and systems for which this is not the case. The results yield a geometric interpretation that can be viewed as an extension of the corresponding interpretation of the geometry of systems undergoing phase equilibria alone. Illustrations are given of all possible cases of binary and ternary reacting systems.     

Hierarchical Self-organization of Complex Systems

Researches on organization and structure in complex systems are academic and industrial fronts in mod-ern sciences. Though many theories are tentatively proposed to analyze complex systems, we still lack a rig-orous theory on them. Complex systems possess various degrees of freedom, which means that they should exhibit all kinds of structures. However, complex systems often show similar patterns and structures. Then the question arises why such similar structures appear in all kinds of complex systems. The paper outlines a theory on freedom degree compression and the existence of hierarchical self-organization for all complex sys-tems is found. It is freedom degree compression and hierarchical self-organization that are responsible for the existence of these similar patterns or structures observed in the complex systems.     

Unveil the potential function of CD in surfactant systems

CDs may have promising functions in surfactant systems far beyond simply being disadvantageous to the formation of micelles. In this paper we review the recent literature and our work on the interesting effect of CDs on amphiphilic systems, especially on the concentrated single surfactant systems and catanionic surfactant mixed systems, both of them have been scarcely focused upon in the literature. In concentrated single surfactant systems, the 2:1 surfactant-CD inclusion complexes may form hierarchical self-assemblies such as lamellae, microtubes, and vesicles which are driven by hydrogen bonding. In nonstoichiometrically mixed catanionic surfactant systems, CDs behave as a stoichiometry booster that always selectively binds to the excess component so as to shift the mixing ratio to electro-neutral in the aggregates. In this way, CDs reduce the electrorepulsion in the aggregates and trigger their growth. Upon analysis of literature work and our own results, we expect that a new era focusing on the new function of CDs on surfactant systems will come.     

Comparison of TEVA<Superscript>®</Superscript> resin beads,PAN fibers,and ePTFE membranes as a solid support for Aliquat-336 in immobilized liquid extraction chromatography for separation of actinides

The following paper covers a comparison of two new systems to traditional TEVA^® resin systems for the analytical separation of actinides by immobilized liquid–liquid extraction using Aliquat-336. The new systems are using expanded polytetrafluroethane (ePTFE) membrane or polyacrylonitrile (PAN) fibers as the solid support. The systems are compared in two ways. First in how much Aliquat-336 they contain with the Vs, ratio of volume of Aliquat-336 to volume of polymeric support, being 0.158, 0.483, and 0.590 for the TEVA^® resin, PAN fibers, and the ePTFE systems, respectively. The second comparison is in their performance capacity of extraction of uranyl chloride anion complex. The fiber and resins systems show similar capacities, and the membrane system being an order of magnitude less than the other systems. A cost comparison demonstrates the savings advantages of using a fiber based support compared with resin and membrane support systems.     

Revision of UNIFAC group interaction parameters of group contribution models to improve prediction results of vapor–liquid equilibria for solvent–polymer systems

The objective of this work was to improve the accuracy of group contribution models for prediction of solvent activities in polymer solutions by revising UNIFAC group interaction parameters using a wide range of vapor–liquid equilibrium (VLE) data of solvent–polymer systems. The group contribution models considered in this work were UNIFAC-FV, Entropic-FV, GK-FV and UNIFAC-ZM models. A total of 142 systems that consisted of 16 polymers and 36 solvents containing a large variety of solvent–polymer systems ranging from non-polar to polar substances were considered to optimize 46 pairs of group interaction parameters. Data considered were split up into systems containing alkane and cycloalkane, aromatic, and polar solvents. For athermal systems, the UNIFAC-FV model gave the best results. Therefore, the model was used in optimizing the group parameters. Revised group interaction parameters were found to improve the reliability of VLE predictions in solvent–polymer systems. A significant improvement of prediction results was achieved by UNIFAC-FV model from 20.0 to 10.8% absolute average deviation (AAD) in solvent activities for systems containing polar solvents and from 16.7 to 10.9% AAD for all systems. The prediction results of GK-FV and UNIFAC-ZM models were also improved.     

分析实验室UPS电源配置与使用维护

对分析实验室仪器配置Uninterruptible Power System（UPS）电源的必要性进行了分析与探讨,介绍了如何合理配置UPS电源的方法,对UPS电源的使用与维护给出了建议。     

Challenges for the Periodic Systems of Elements: Chemical,Historical and Mathematical Perspectives

We celebrate 150 years of periodic systems that reached their maturity in the 1860s. They began as pedagogical efforts to project corpuses of substances on the similarity and order relationships of the chemical elements. However, these elements are not the canned substances wrongly displayed in many periodic tables, but rather the abstract preserved entities in compound transformations. We celebrate the systems, rather than their tables or ultimate table. The periodic law, we argue, is not an all-encompassing achievement, as it does not apply to every property of all elements and compounds. Periodic systems have been generalised as ordered hypergraphs, which solves the long-lasting question on the mathematical structure of the systems. In this essay, it is shown that these hypergraphs may solve current issues such as order reversals in super-heavy elements and lack of system predictive power. We discuss research in extending the limits of the systems in the super-heavy-atom region and draw attention to other limits: the antimatter region and the limit arising from compounds under extreme conditions. As systems depend on the known chemical substances (chemical space) and such a space grows exponentially, we wonder whether systems still aim at projecting knowledge of compounds on the relationships among the elements. We claim that systems are not based on compounds anymore, rather on 20th century projections of the 1860s systems of elements on systems of atoms. These projections bring about oversimplifications based on entities far from being related to compounds. A linked oversimplification is the myth of vertical group similarity, which raises questions on the approaches to locate new elements in the system. Finally, we propose bringing back chemistry to the systems by exploring similarity and order relationships of elements using the current information of the chemical space. We ponder whether 19th century periodic systems are still there or whether they have faded away, leaving us with an empty 150^th celebration.