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

Nanocrystals are fundamental to modern science and technology. Mastery over the shape of a nanocrystal enables control of its properties and enhancement of its usefulness for a given application. Our aim is to present a comprehensive review of current research activities that center on the shape-controlled synthesis of metal nanocrystals. We begin with a brief introduction to nucleation and growth within the context of metal nanocrystal synthesis, followed by a discussion of the possible shapes that a metal nanocrystal might take under different conditions. We then focus on a variety of experimental parameters that have been explored to manipulate the nucleation and growth of metal nanocrystals in solution-phase syntheses in an effort to generate specific shapes. We then elaborate on these approaches by selecting examples in which there is already reasonable understanding for the observed shape control or at least the protocols have proven to be reproducible and controllable. Finally, we highlight a number of applications that have been enabled and/or enhanced by the shape-controlled synthesis of metal nanocrystals. We conclude this article with personal perspectives on the directions toward which future research in this field might take.

Shape‐Controlled Synthesis of Metal Nanocrystals: Simple Chemistry Meets Complex Physics?

5.1. Nanoalloys of Group 11 (Cu, Ag, Au) 865 5.1.1. Cu−Ag 866 5.1.2. Cu−Au 867 5.1.3. Ag−Au 870 5.1.4. Cu−Ag−Au 872 5.2. Nanoalloys of Group 10 (Ni, Pd, Pt) 872 5.2.1. Ni−Pd 872 * To whom correspondence should be addressed. Phone: +39010 3536214. Fax:+39010 311066. E-mail: ferrando@fisica.unige.it. † Universita di Genova. ‡ Argonne National Laboratory. § University of Birmingham. | As of October 1, 2007, Chemical Sciences and Engineering Division. Volume 108, Number 3

Nanoalloys: From Theory to Applications of Alloy Clusters and Nanoparticles

Supported metal nanostructures are the most widely used type of heterogeneous catalyst in industrial processes. The size of metal particles is a key factor in determining the performance of such catalysts. In particular, because low-coordinated metal atoms often function as the catalytically active sites, the specific activity per metal atom usually increases with decreasing size of the metal particles. However, the surface free energy of metals increases significantly with decreasing particle size, promoting aggregation of small clusters. Using an appropriate support material that strongly interacts with the metal species prevents this aggregation, creating stable, finely dispersed metal clusters with a high catalytic activity, an approach industry has used for a long time. Nevertheless, practical supported metal catalysts are inhomogeneous and usually consist of a mixture of sizes from nanoparticles to subnanometer clusters. Such heterogeneity not only reduces the metal atom efficiency but also frequent...

Single-atom catalysts: a new frontier in heterogeneous catalysis.

: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Photoelectron spectroscopy revealed that a 20-atom gold cluster has an extremely large energy gap, which is even greater than that of C60, and an electron affinity comparable with that of C60. This observation suggests that the Au20 cluster should be highly stable and chemically inert. Using relativistic density functional calculations, we found that Au20 possesses a tetrahedral structure, which is a fragment of the face-centered cubic lattice of bulk gold with a small structural relaxation. Au20 is thus a unique molecule with atomic packing similar to that of bulk gold but with very different properties.

http://cluster.physik.uni-freiburg.de/lehre/SS11/ueb11/Li2003b.pdf

Au20: A Tetrahedral Cluster

We report a joint experimental and theoretical study of the electronic and atomic structures of small gold clusters with up to 14 atoms. Well-resolved photoelectron spectra were obtained for AuN- (N = 1−14) at several photon energies. Even−odd alternations were observed, where the even-sized clusters (except Au10-) exhibit an energy gap between the lowest binding energy peak and the rest of the spectrum, indicating that all the neutral even-sized clusters have closed shells. The Au10- spectrum reveals the existence of isomers, with the ground-state cluster exhibiting an extremely high electron binding energy. Evidence of multiple isomers was also observed in the spectra of N = 4, 8, 12, and 13. The structures of the gold cluster anions in the range N = 4−14 were investigated using first-principles simulations. A striking feature of the anionic clusters in this range is the occurrence of planar ground-state structures, which were predicted in earlier theoretical studies (Hakkinen, H.; et al. Phys. Rev. Let...

On the Electronic and Atomic Structures of Small AuN- (N = 4−14) Clusters: A Photoelectron Spectroscopy and Density-Functional Study

Aromaticity is a concept invented to account for the unusual stability of an important class of organic molecules: the aromatic compounds. Here we report experimental and theoretical evidence of aromaticity in all-metal systems. A series of bimetallic clusters with chemical composition MAl4– (M = Li, Na, or Cu), was created and studied with photoelectron spectroscopy and ab initio calculations. All the MAl4– species possess a pyramidal structure containing an M+ cation interacting with a square Al42– unit. Ab initio studies indicate that Al42– exhibits characteristics of aromaticity with two delocalized π electrons (thus following the 4n + 2 electron counting rule) and a square planar structure and maintains its structural and electronic features in all the MAl4– complexes. These findings expand the aromaticity concept into the arena of all-metal species.

https://science.sciencemag.org/content/sci/291/5505/859.full.pdf

Observation of all-metal aromatic molecules.

The fullerenes are the first “free-standing” elemental hollow cages identified by spectroscopy experiments and synthesized in the bulk. Here, we report experimental and theoretical evidence of hollow cages consisting of pure metal atoms, Aun− (n = 16–18); to our knowledge, free-standing metal hollow cages have not been previously detected in the laboratory. These hollow golden cages (“bucky gold”) have an average diameter >5.5 A, which can easily accommodate one guest atom inside.

/pdf/evidence-of-hollow-golden-cages-2e7qzidinm.pdf

Evidence of hollow golden cages

The recently predicted W@Au12 cluster has been observed and probed experimentally using anion photoelectron spectroscopy. It is shown that this unique molecule and its Mo congener indeed possess an icosahedral structure and a large HOMO-LUMO gap. Relativistic density functional theory is used to calculate their geometries, energetics, and energy spectra. The simulated density-of-states spectra are in good agreement with the photoelectron spectra, confirming the icosahedral structure of these complexes.

Xi Li

Papers

Au20: A Tetrahedral Cluster

On the Electronic and Atomic Structures of Small AuN- (N = 4−14) Clusters: A Photoelectron Spectroscopy and Density-Functional Study

Observation of all-metal aromatic molecules.

Evidence of hollow golden cages

Experimental observation and confirmation of icosahedral W@Au12 and Mo@Au12 molecules.