Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

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

Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles and self-assembled monolayers (SAMs). We will limit the present review to gold nanoparticles (AuNPs), also called gold colloids. AuNPs are the most stable metal nanoparticles, and they present fascinating aspects such as their assembly of multiple types involving materials science, the behavior of the individual particles, size-related electronic, magnetic and optical properties (quantum size effect), and their applications to catalysis and biology. Their promises are in these fields as well as in the bottom-up approach of nanotechnology, and they will be key materials and building block in the 21st century. Whereas the extraction of gold started in the 5th millennium B.C. near Varna (Bulgaria) and reached 10 tons per year in Egypt around 1200-1300 B.C. when the marvelous statue of Touthankamon was constructed, it is probable that “soluble” gold appeared around the 5th or 4th century B.C. in Egypt and China. In antiquity, materials were used in an ecological sense for both aesthetic and curative purposes. Colloidal gold was used to make ruby glass 293 Chem. Rev. 2004, 104, 293−346

Gold nanoparticles: assembly, supramolecular chemistry, quantum-size-related properties, and applications toward biology, catalysis, and nanotechnology.

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

A stepwise huisgen cycloaddition process: copper(I)-catalyzed regioselective "ligation" of azides and terminal alkynes.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/ange.201209124

Editorial: Von der supramolekularen zur Systemchemie: vom Einfachen zum Komplexen

Durch selbstassoziation zu isomeren 2-catenanen

Complexes of primary alkylammonium salts and secondary dialkylammonium salts with diazaparacyclophanes

Several different approaches to the stereoselective synthesis of xylitol (1), as well as the other two pentitols, ribitol (2) and DL-arabinitol DL-(3), from the (Z)- and (E)-1-hydroxpentadienes (4) and (5) and the (Z)- and (E)-4,5-epoxypent-2-enals (6) and (7) are described. They rely upon either (a) epoxidations of allylic CC double bonds followed by stereospecific (anti) and sometimes regioselective epoxide cleavages, or (b)syn-hydroxylations of allylic CC double bonds. Employing approach (a), the (Z)-isomers (4) and (6) do not afford any ribitol (2) among the products and the (E)-isomers do not afford any xylitol (1). The consequences are reversed when approach (b) is adopted. The most convenient synthesis of xylitol (1) starts from the (Z)-isomer (6) of 4,5-epoxypent-2-enal. The formyl group in (6) is reduced, provided acidic work-up conditions are employed, to yield (Z)-(4RS)-4,5-epoxy-1-hydroxypent-2-ene (9), which is characterised as its acetate (10). Opening of the epoxide ring in (10) with acetate ion gives the triacetate (11), which is deacetylated to afford a key intermediate, (Z)-(4RS)-1,4,5-trihydroxypent-2-ene (12). Epoxidation of (12) with peracids (e.g. p-nitroperbenzoic acid) yields (t-butyl hydroperoxide with catalytically active Ti4+, V5+, and Mo6+ complexes fails) two epoxides (13) and (14), arbitrarily named isomers A (13) and B (14) subsequently shown to have the relative stereochemistries (2S,3R,4R) and (2R,3R,4R), respectively. Epoxide ring opening with acetate ion in acetic anhydride of the more abundant isomer B (14), obtained with 70% diastereoselectivity, yields xylitol penta-acetate (16) as the major product (>80% diastereoselectivity) along with small and trace amounts of the other two pentitol penta-acetates. Epoxide ring opening of isomer A with acetate ion in acetic anhydride is not a straightforward reaction for the most part and has been found to involve the intermediacy of an isolatable bicyclic orthoester (23)en route to some of the xylitol penta-acetate (16) formed as the principal stable product during this reaction. These variations of approach (a) constitute stereoselective syntheses of xylitol (1), which are claimed to be acceptable on a laboratory scale. They provide a slightly better route than an alternative one involving the transformations (4)→(33)→(34)→(39)→(16)→(1), starting from (Z)-1-hydroxypenta-2,4-diene (4), principally because this particular precursor is less readily accessible than (Z)-4,5-epoxypent-2-enal (6). By contrast, the (E)-isomer (5) of 1-hydroxypenta-2,5-diene is obtainable in high yield from the reduction of vinyl acrylic acid and the analogous transformations [(5)→(26)→(27)→(28)→DL-(5)→DL-(3)] provide a highly stereoselective (91%) synthetic route to DL-arabinitiol DL-(3). Osmium-catalysed syn-hydroxylation of (E)-(4RS)-triacetoxypent-2-ene (22), prepared from (E)-4,5-epoxypent-2-enal (7) in two steps [(7)→(20)→(22)], provides yet another approach to DL-arabinitol DL-(3), but the stereoselectivity (76%) of this oxidation is not as good as that observed for the epoxidation of rel-(3R,4R)-3,4,5-triacetoxypent-1-ene (27) in the above transformation. The synthesis of ribitol (2) by osmium-catalysed syn-hydroxylation of the (Z)-isomer (11) of (22) was achieved with a modest stereoselectivity of 66% for the oxidation step.

J. Fraser Stoddart

Papers

Editorial: Von der supramolekularen zur Systemchemie: vom Einfachen zum Komplexen

Durch selbstassoziation zu isomeren 2-catenanen

Complexes of primary alkylammonium salts and secondary dialkylammonium salts with diazaparacyclophanes

Regioselective and stereoselective methods for the synthesis of the pentitols

Self‐Assembly and Self‐Organization of Self‐Recognizing Cyclophanes