抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Crystalline metal-organic frameworks (MOFs) are formed by reticular synthesis, which creates strong bonds between inorganic and organic units. Careful selection of MOF constituents can yield crystals of ultrahigh porosity and high thermal and chemical stability. These characteristics allow the interior of MOFs to be chemically altered for use in gas separation, gas storage, and catalysis, among other applications. The precision commonly exercised in their chemical modification and the ability to expand their metrics without changing the underlying topology have not been achieved with other solids. MOFs whose chemical composition and shape of building units can be multiply varied within a particular structure already exist and may lead to materials that offer a synergistic combination of properties.

The Chemistry and Applications of Metal-Organic Frameworks

This critical review will be of interest to the experts in porous solids (including catalysis), but also solid state chemists and physicists. It presents the state-of-the-art on hybrid porous solids, their advantages, their new routes of synthesis, the structural concepts useful for their ‘design’, aiming at reaching very large pores. Their dynamic properties and the possibility of predicting their structure are described. The large tunability of the pore size leads to unprecedented properties and applications. They concern adsorption of species, storage and delivery and the physical properties of the dense phases. (323 references)

Hybrid porous solids: past, present, future

New materials capable of storing hydrogen at high gravimetric and volumetric densities are required if hydrogen is to be widely employed as a clean alternative to hydrocarbon fuels in cars and other mobile applications. With exceptionally high surface areas and chemically-tunable structures, microporous metal–organic frameworks have recently emerged as some of the most promising candidate materials. In this critical review we provide an overview of the current status of hydrogen storage within such compounds. Particular emphasis is given to the relationships between structural features and the enthalpy of hydrogen adsorption, spectroscopic methods for probing framework–H2 interactions, and strategies for improving storage capacity (188 references).

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Hydrogen storage in metal–organic frameworks

Metal-organic framework-5 (MOF-5) of composition Zn4O(BDC)3 (BDC = 1,4-benzenedicarboxylate) with a cubic three-dimensional extended porous structure adsorbed hydrogen up to 4.5 weight percent (17.2 hydrogen molecules per formula unit) at 78 kelvin and 1.0 weight percent at room temperature and pressure of 20 bar. Inelastic neutron scattering spectroscopy of the rotational transitions of the adsorbed hydrogen molecules indicates the presence of two well-defined binding sites (termed I and II), which we associate with hydrogen binding to zinc and the BDC linker, respectively. Preliminary studies on topologically similar isoreticular metal-organic framework-6 and -8 (IRMOF-6 and -8) having cyclobutylbenzene and naphthalene linkers, respectively, gave approximately double and quadruple (2.0 weight percent) the uptake found for MOF-5 at room temperature and 10 bar.

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Hydrogen Storage in Microporous Metal-Organic Frameworks

The use of co-adsorption studies of N{sub 2} with H{sub 2} makes it possible to obtain information about adsorption of N{sub 2} by monitoring changes in the rotational spectrum of the co-adsorbed H{sub 2} molecules. We present such results on N{sub 2}/H{sub 2} in Na-13X.

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Co-adsorption studies of hydrogen with nitrogen in zeolites

The molecular role of organotin promoters, which confer functional group tolerance on supported Re catalysts for olefin metathesis, was explored through spectroscopic and computational analysis, as well as kinetic studies. On dehydrated silica and silica-alumina, the addition of SnMe4 results in two surface reactions: (i) in situ generation of MeReO3; and (ii) capping of Bronsted acid sites. The former is responsible for catalytic activity towards polar α-olefins; thus, an independentlyprepared sample of MeReO3/silica-alumina catalyzed the homometathesis of methyl3-butenoate. The latter stabilizes the catalyst: in sequential batch reactor tests involving propylene homometathesis, MeReO3 deposited on silica-alumina capped with hexamethyldisilazane (to eliminate Bronsted acidity) showed activity identical to that of the perrhenate/silica-alumina catalyst promoted with SnMe4. Thus, a completely Sn-free catalyst performs metathesis as efficiently as the organotincontaining perrhenate catalyst.

Supported Re Catalysts for Metathesis of Functionalized Olefins

A series of cycled Ni battery plate materials has been examined by means of inelastic neutron scattering spectroscopy in order to determine the nature of the protons in the discharged and cycled material. Our results clearly demonstrate that some amount of the NiOOH phases which form on oxidation does not convert back to β-Ni(OH) upon discharging the battery and that this amount increases with the number of cycles the battery undergoes. Moreover, we have identified vibrational signatures of lattice water and found that its amount increases with KOH concentration used in the cell. Since cells operated at higher KOH concentrations are known to fail after fewer cycles, our inelastic neutron scattering studies clearly implicate the irreversible formation of lattice water as one of the main reasons for this failure.

Effects of Cycling Conditions of Active Material from Discharged Ni Positive Plates Studied by Inelastic Neutron Scattering Spectroscopy

The Monte Carlo method is a powerful technique for neutron transport studies. While it has been applied for many years to the study of nuclear systems, there are few codes available for neutron transport in the optical regime. The recent surge of interest in so-called next generation spallation neutron sources and the desire to design new and optimized instruments for these facilities has led us to develop a Monte Carlo code geared toward the simulation of neutron scattering instruments. The time-of-flight multichopper spectrometer, of which IN5 at the ILL is the prototypical example, is the first spectrometer studied with the code. Some of the results of a comparison between the IN5 performance at a reactor and at a Long Pulse Spallation Source (LPSS) are summarized here.

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Juergen Eckert

Papers

Co-adsorption studies of hydrogen with nitrogen in zeolites

Supported Re Catalysts for Metathesis of Functionalized Olefins

Effects of Cycling Conditions of Active Material from Discharged Ni Positive Plates Studied by Inelastic Neutron Scattering Spectroscopy

Monte Carlo study of the performance of a time-of-flight multichopper spectrometer

Synthesis, characterization and properties of the new ionic intercalation compound (NH+4)0.22TiS0.22−2