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

A revolution in novel nanoparticles and colloidal building blocks has been enabled by recent breakthroughs in particle synthesis These new particles are poised to become the ‘atoms’ and ‘molecules’ of tomorrow’s materials if they can be successfully assembled into useful structures Here, we discuss the recent progress made in the synthesis of nanocrystals and colloidal particles and draw analogies between these new particulate building blocks and better-studied molecules and supramolecular objects We argue for a conceptual framework for these new building blocks based on anisotropy attributes and discuss the prognosis for future progress in exploiting anisotropy for materials design and assembly

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Anisotropy of building blocks and their assembly into complex structures

Journal of Physics Condensed Matter: Preface

A challenging goal in materials chemistry and physics is spontaneously to form intended superstructures from designed building blocks. In fields such as crystal engineering and the design of porous materials, this typically involves building blocks of organic molecules, sometimes operating together with metallic ions or clusters. The translation of such ideas to nanoparticles and colloidal-sized building blocks would potentially open doors to new materials and new properties, but the pathways to achieve this goal are still undetermined. Here we show how colloidal spheres can be induced to self-assemble into a complex predetermined colloidal crystal-in this case a colloidal kagome lattice-through decoration of their surfaces with a simple pattern of hydrophobic domains. The building blocks are simple micrometre-sized spheres with interactions (electrostatic repulsion in the middle, hydrophobic attraction at the poles, which we call 'triblock Janus') that are also simple, but the self-assembly of the spheres into an open kagome structure contrasts with previously known close-packed periodic arrangements of spheres. This open network is of interest for several theoretical reasons. With a view to possible enhanced functionality, the resulting lattice structure possesses two families of pores, one that is hydrophobic on the rims of the pores and another that is hydrophilic. This strategy of 'convergent' self-assembly from easily fabricated colloidal building blocks encodes the target supracolloidal architecture, not in localized attractive spots but instead in large redundantly attractive regions, and can be extended to form other supracolloidal networks.

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Directed self-assembly of a colloidal kagome lattice

Controlling interparticle interactions, aggregation and cluster formation is of central importance in a number of areas, ranging from cluster formation in various disease processes to protein crystallography and the production of photonic crystals. Recent developments in the description of the interaction of colloidal particles with short-range attractive potentials have led to interesting findings including metastable liquid-liquid phase separation and the formation of dynamically arrested states (such as the existence of attractive and repulsive glasses, and transient gels). The emerging glass paradigm has been successfully applied to complex soft-matter systems, such as colloid-polymer systems and concentrated protein solutions. However, intriguing problems like the frequent occurrence of cluster phases remain. Here we report small-angle scattering and confocal microscopy investigations of two model systems: protein solutions and colloid-polymer mixtures. We demonstrate that in both systems, a combination of short-range attraction and long-range repulsion results in the formation of small equilibrium clusters. We discuss the relevance of this finding for nucleation processes during protein crystallization, protein or DNA self-assembly and the previously observed formation of cluster and gel phases in colloidal suspensions.

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Equilibrium cluster formation in concentrated protein solutions and colloids

Continuous phase transitions are characterized by universality: thermodynamic observables that diverge with power-law exponents whose values are governed by symmetry considerations and are insensitive to other details of the materials [1, 2] The nematic-smectic-A (NA) transition, where an ordered liquid acquires additional one-dimensional periodicity is one of the outstanding unsolved problems in this field of study [3, 4] Here the critical behaviour appears non-universal The order of the transition has been a matter of debate The complexity of the NA transition arises from an intrinsic coupling between two order parameters Indeed, even the direct determination of mean-field parameters has been a matter of recent study Due to this complexity, there are still unresolved issues after more than three decades of research The subtleties involved have been addressed theoretically via different approximations, leading to a rich addition to the phase transitions literature Experimentally, these subtleties have inspired precise high-resolution experiments This article focuses on experimental developments in the last decade that address aspects of the nature of the NA transition

Recent Experimental Developments at the Nematic to Smectic-A Liquid Crystal Phase Transition

Micromagnetic modeling provides a realistic description of the magnetic switching behavior in electrodeposited Co thin films that are either uniform (untemplated) or templated with an array of sub-micron spheres. Quantitative agreement between experimental results and simulations based on the Landau-Lifshitz-Gilbert equations is achieved for both in-plane and perpendicular MH loops at two temperatures. By accounting for the sweep-rate dependence in coercivity values from simulated loops (with sweep rates 104–10−1 Oe/ns) and then extrapolating to the experimental regime (measurement times of 10–100 s), a self-consistent set of microscopic parameters is established to accommodate the complexity of the electrodeposited films.

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Micromagnetic modeling of experimental hysteresis loops for heterogeneous electrodeposited cobalt films

We characterize the superdiffusive dynamics of tracer particles in an electrohydrodynamically driven emulsion of oil droplets in an immiscible oil medium, where the amplitude and frequency of an external electric field are the control parameters. In the weakly driven electrohydrodynamic regime, the droplets are trapped dielectrophoretically on a patterned electrode, and the driving is therefore spatially varying. We find excellent agreement with a $\ensuremath{\langle}{x}^{2}\ensuremath{\rangle}\ensuremath{\sim}{t}^{1.5}$ power law and find that this superdiffusive dynamics arises from an underlying displacement distribution that is distinctly non-Gaussian and exponential for small displacements and short times. While these results are comparable with a random-velocity field model, the tracer particle speeds are in fact spatially varying in two dimensions, arising from a spatially varying electrohydrodynamic driving force. This suggests that the important ingredient for the superdiffusive ${t}^{1.5}$ behavior observed is a velocity field that is isotropic in the plane and spatially correlated. Finally, we can extract, from the superdiffusive dynamics, a experimental length scale that corresponds to the lateral range of the hydrodynamic flows. This experimental length scale is non zero only above a threshold ion mobility length.

Anomalous dynamics in tracer-particle motions in an electrohydrodynamically driven oil-in-oil system.

High-resolution study of fluctuation effects at the nematic-smectic-A phase transition

Correction for 'Tunable hydrodynamics: a field-frequency phase diagram of a non-equilibrium order-to-disorder transition' by Somayeh Khajehpour Tadavani et al., Soft Matter, 2017, 13, 7412-7424.

https://pubs.rsc.org/en/content/articlepdf/2018/SM/C8SM90196A

Anand Yethiraj

Papers

Recent Experimental Developments at the Nematic to Smectic-A Liquid Crystal Phase Transition

Micromagnetic modeling of experimental hysteresis loops for heterogeneous electrodeposited cobalt films

Anomalous dynamics in tracer-particle motions in an electrohydrodynamically driven oil-in-oil system.

High-resolution study of fluctuation effects at the nematic-smectic-A phase transition

Tunable hydrodynamics: a field-frequency phase diagram of a non-equilibrium order-to-disorder transition