J. Fraser Stoddart

Bio: J. Fraser Stoddart is an academic researcher from Northwestern University. The author has contributed to research in topics: Catenane & Supramolecular chemistry. The author has an hindex of 147, co-authored 1239 publications receiving 96083 citations. Previous affiliations of J. Fraser Stoddart include Zhejiang University & Northwest University (United States).

Radically Enhanced Dual Recognition.

Abstract: Complexation between a viologen radical cation (V.+ ) and cyclobis(paraquat-p-phenylene) diradical dication (CBPQT2(.+) ) has been investigated and utilized extensively in the construction of mechanically interlocked molecules (MIMs) and artificial molecular machines (AMMs). The selective recognition of a pair of V.+ using radical-pairing interactions, however, remains a formidable challenge. Herein, we report the efficient encapsulation of two methyl viologen radical cations (MV.+ ) in a size-matched bisradical dicationic host - namely, cyclobis(paraquat-2,6-naphthalene)2(.+) , i.e., CBPQN2(.+) . Central to this dual recognition process was the choice of 2,6-bismethylenenaphthalene linkers for incorporation into the bisradical dicationic host. They provide the space between the two bipyridinium radical cations in CBPQN2(.+) suitable for binding two MV.+ with relatively short (3.05-3.25 A) radical-pairing distances. The size-matched bisradical dicationic host was found to exhibit highly selective and cooperative association with the two MV.+ in MeCN at room temperature. The formation of the tetrakisradical tetracationic inclusion complex - namely, [(MV)2 ⊂CBPQN]4(.+) - in MeCN was confirmed by VT 1 H NMR, as well as by EPR spectroscopy. The solid-state superstructure of [(MV)2 ⊂CBPQN]4(.+) reveals an uneven distribution of the binding distances (3.05, 3.24, 3.05 A) between the three different V.+ , suggesting that localization of the radical-pairing interactions has a strong influence on the packing of the two MV.+ inside the bisradical dicationic host. Our findings constitute a rare example of binding two radical guests with high affinity and cooperativity using host-guest radical-pairing interactions. Moreover, they open up possibilities of harnessing the tetrakisradical tetracationic inclusion complex as a new, orthogonal and redox-switchable recognition motif for the construction of MIMs and AMMs.

Macrocyclic polyethers incorporating resorcinol residues as templates for cyclobis(paraquat-p-phenylene) in the self-assembly of [2]catenanes

Abstract: The self-assembly of [2]catenanes incorporating cyclobis(paraquat-p-phenylene) and either bis(metaphenylene)-32-crown-10 or tris(metaphenylene)-48-crown-15 has been achieved. The dynamic processes associated with the relative motions of the two rings have been studied by variable temperature 1H NMR spectroscopy. Both [2]catenanes display rapid relative movements of the two components, associated with free energies of activation in the region 12–14 kcal mol−1 for different processes. The resorcinol residues of the macrocyclic polyethers are bound in the cavity of the cyclophane by π-π stacking, electrostatic interactions, and T-type hydrogen bonding.

Recognition between V- and dumbbell-shaped molecules

Abstract: A series of 2,6-bis(imino)pyridyl-based V-shaped compounds bearing various para-substituents on the terminal aromatic rings [C5H3N(CHN–C6H4R)2; R = OMe, iPr, Me, H, Cl, F, and CF3] have been prepared and investigated for their reversible binding with the dumbbell-shaped cations NH2+–{CH2–C6H3(OMe-3,5)2}2 and 9-anthryl–CH2–NH2+–CH2–C6H3(OMe-3,5)2. Three crystalline V-shaped compounds and a dumbbell hexafluorophosphate were characterised in the solid state by X-ray structural analysis. The binding mode of the 1 : 1 V-shaped molecule·dumbbell complexes was evaluated by 1H NMR spectroscopy. The binding constants (90–400 M−1 in dichloromethane) and stoichiometries of the complexes were determined using the Method of Continuous Variations and the Rose-Drago Method based on 1H NMR spectroscopic data. In a series of V-shaped compounds, the binding strength with both dumbbell cations diminishes with the decreasing electron-donating ability of the R substituents. Specifically, one of the diimine V-shaped compounds shows a stronger binding with the symmetrical dumbbell than with the unsymmetrical anthracene-containing dumbbell. Fluorescence measurements of equimolar mixtures of the V-shaped compounds and the unsymmetrical dumbbell have revealed a reduced anthracene emission which is approximately 50% that of the original intensity. Rapid and complete dissociation (<5 min) of the V-shaped compounds from the dumbbells was realised using an excess of acid or base, whereas only partial dissociation of the complexes was achieved with a large excess of water (<1 h).

Fast parallel algorithms for short-range molecular dynamics

Abstract: 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.

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

Abstract: 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。

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

Abstract: 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

The Chemistry and Applications of Metal-Organic Frameworks

Abstract: 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.