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

Single-molecule force spectroscopy has emerged as a powerful tool to investigate the forces and motions associated with biological molecules and enzymatic activity. The most common force spectroscopy techniques are optical tweezers, magnetic tweezers and atomic force microscopy. Here we describe these techniques and illustrate them with examples highlighting current capabilities and limitations.

Single-molecule force spectroscopy: optical tweezers, magnetic tweezers and atomic force microscopy

Silicon is an attractive material for anodes in energy storage devices1,2,3, because it has ten times the theoretical capacity of its state-of-the-art carbonaceous counterpart. Silicon anodes can be used both in traditional lithium-ion batteries and in more recent Li–O2 and Li–S batteries as a replacement for the dendrite-forming lithium metal anodes. The main challenges associated with silicon anodes are structural degradation and instability of the solid-electrolyte interphase caused by the large volume change (∼300%) during cycling, the occurrence of side reactions with the electrolyte, and the low volumetric capacity when the material size is reduced to a nanometre scale4,5,6,7. Here, we propose a hierarchical structured silicon anode that tackles all three of these problems. Our design is inspired by the structure of a pomegranate, where single silicon nanoparticles are encapsulated by a conductive carbon layer that leaves enough room for expansion and contraction following lithiation and delithiation. An ensemble of these hybrid nanoparticles is then encapsulated by a thicker carbon layer in micrometre-size pouches to act as an electrolyte barrier. As a result of this hierarchical arrangement, the solid-electrolyte interphase remains stable and spatially confined, resulting in superior cyclability (97% capacity retention after 1,000 cycles). In addition, the microstructures lower the electrode–electrolyte contact area, resulting in high Coulombic efficiency (99.87%) and volumetric capacity (1,270 mAh cm−3), and the cycling remains stable even when the areal capacity is increased to the level of commercial lithium-ion batteries (3.7 mAh cm−2). A Si anode with hierarchical morphology can accommodate large volume changes, demonstrates high Coulombic efficiency and cyclability as well as an areal capacity comparable to that of commercial Li-ion batteries.

A pomegranate-inspired nanoscale design for large-volume-change lithium battery anodes

The discovery of the enhancement of Raman scattering by molecules adsorbed on nanostructured metal surfaces is a landmark in the history of spectroscopic and analytical techniques. Significant experimental and theoretical effort has been directed toward understanding the surface-enhanced Raman scattering (SERS) effect and demonstrating its potential in various types of ultrasensitive sensing applications in a wide variety of fields. In the 45 years since its discovery, SERS has blossomed into a rich area of research and technology, but additional efforts are still needed before it can be routinely used analytically and in commercial products. In this Review, prominent authors from around the world joined together to summarize the state of the art in understanding and using SERS and to predict what can be expected in the near future in terms of research, applications, and technological development. This Review is dedicated to SERS pioneer and our coauthor, the late Prof. Richard Van Duyne, whom we lost during the preparation of this article.

/pdf/present-and-future-of-surface-enhanced-raman-scattering-34aqgcm385.pdf

Present and Future of Surface-Enhanced Raman Scattering

Coating is an essential step in adjusting the surface properties of materials. Superhydrophobic coatings with contact angles greater than 150° and roll-off angles below 10° for water have been developed, based on low-energy surfaces and roughness on the nano- and micrometer scales. However, these surfaces are still wetted by organic liquids such as surfactant-based solutions, alcohols, or alkanes. Coatings that are simultaneously superhydrophobic and superoleophobic are rare. We designed an easily fabricated, transparent, and oil-rebounding superamphiphobic coating. A porous deposit of candle soot was coated with a 25-nanometer-thick silica shell. The black coating became transparent after calcination at 600°C. After silanization, the coating was superamphiphobic and remained so even after its top layer was damaged by sand impingement.

Candle Soot as a Template for a Transparent Robust Superamphiphobic Coating

Colloidal self-assembly has been investigated as a promising and practical approach for the fabrication of photonic nanostructures, including colloidal crystals, composite and inverse opals, and photonic glasses. Depending on the interactions between the colloidal particles, colloidal structures can be affected dramatically and modulated by applying an additional external field. Furthermore, in contrast to other approaches, self-assembled nanostructures with large areas or designed shapes can be prepared at low cost. As a result, the use of such colloidal systems has been investigated in many practical photonic applications. In this review article, we describe the colloidal self-assembly of periodic and non-periodic photonic nanostructures in brief and then summarize recent achievements in the field of colloidal photonic nanostructures and their applications, which include displays, optical devices, photochemistry and biological sensors.

/pdf/self-assembled-colloidal-structures-for-photonics-2ub3985ctw.pdf

Self-assembled colloidal structures for photonics

We use digital holographic microscopy and Mie scattering theory to simultaneously characterize and track individual colloidal particles. Each holographic snapshot provides enough information to measure a colloidal sphere's radius and refractive index to within 1%, and simultaneously to measure its three-dimensional position with nanometer in-plane precision and 10 nanometer axial resolution.

http://physics.nyu.edu/grierlab/index12c/index12c.pdf

Characterizing and tracking single colloidal particles with video holographic microscopy

Synthesis and self-assembly of structured colloids is a nascent field. Recent advances in this area include the development of a variety of practical routes to produce robust photonic band-gap materials, colloidal lithography for nanopatterns, and hierarchically structured porous materials with high surface-to-volume ratios for catalyst supports. To improve their properties, non-conventional suprastructures have been proposed, which could be built up using binary or bimodal mixtures of spherical particles and particles with internal or surface nanostructures. This Feature Article will describe the state-of-the-art in colloidal particles and their assemblies. The paper consists of three main sections categorized by the type of colloid, namely shape-anisotropic particles, chemically patterned particles and internally structured particles. In each section, we will discuss not only synthetic routes to uniform colloids with a range of structures, features and shapes, but also self-organization of these colloids into macrocrystalline structures with varying nanoscopic features and functionalities. Finally, we will outline future perspectives for these colloidal suprastructures.

Synthesis and assembly of structured colloidal particles

Self-assembly of monodisperse colloidal particles into regular lattices has provided relatively simple and economical methods to prepare photonic crystals. The photonic stop band of colloidal crystals appears as opalescent structural colors, which are potentially useful for display devices, colorimetric sensors, and optical filters. However, colloidal crystals have low durability, and an undesired scattering of light makes the structures white and translucent. Moreover, micropatterning of colloidal crystals usually requires complex molding procedures, thereby limiting their practical applications. To overcome such shortcomings, we develop a pragmatic and amenable method to prepare colloidal photonic crystals with high optical transparency and physical rigidity using photocurable colloidal suspensions. The colloidal particles dispersed in a photocurable medium crystallized during capillary force-induced infiltration into a slab, and subsequent photopolymerization of the medium permanently solidifies the st...

Colloidal Photonic Crystals toward Structural Color Palettes for Security Materials

Polymersomes are vesicles which consist of compartments surrounded by membrane walls that are composed of lamellae of block copolymers; these are important for numerous applications in encapsulation and delivery of active ingredients such as food additives, drugs, fragrances and enzymes [2] . Polymersomes are typically prepared by precipitating block copolymers from their solvents through addition of a poor solvent for the copolymers, or by rehydrating a dried film of the copolymers. The unfavorable interactions between blocks in the copolymer and the poor solvent induce formation of aggregate structures ranging from micelles, wormlike micelles and vesicles. However, the resultant polymersomes are highly polydisperse and have poor encapsulation efficiency. Recently, a new approach has been developed to fabricate monodisperse polymersomes by using double emulsions as templates. Water-in-oil-in-water (W/O/W) double emulsions with a core-shell structure are first prepared in capillary microfluidic devices. Diblock copolymers, dissolved in the oil shell phase, assemble onto the walls of the polymersomes upon removal of the oil by evaporation 7] after adhesion of the diblock copolymeradsorbed interfaces. This approach leads to polymersomes with high size uniformity and excellent encapsulation efficiency; it also enables precise tuning of the polymersome structures. Advances in techniques for fabricating polymersomes have led to controlled spherical polymersomes with a single compartment. However, non-spherical capsules with multiple compartments also have great potential for encapsulation and delivery applications. By storing incompatible actives or functional components separately, polymersomes with multiple compartments can achieve encapsulation of multiple actives in single capsules and reduce the risk of cross contamination. Moreover, multiple reactants can be encapsulated separately to allow reaction upon triggering. By tuning the number of compartments containing each reactant, the stoichiometric ratio of the reactants for each reaction can be manipulated. These multi-compartment polymersomes will create new opportunities to deliver not only multiple functional components, but also multiple reactants for reactions on demand. In addition, with the versatility of synthetic polymer chemistry to tune properties such as polymer length, biocompatibility, functionality and degradation rates, non-spherical polymersomes with multiple compartments can be tailored for specific delivery targets. However, polymersomes that have been reported to date are almost exclusively spherical in shape, and have only one compartment; since most conventional polymersome fabrication processes rely on self-assembly of the block copolymer lamellae, little control over the size and structure of the resultant polymersomes is achieved. With the conventional emulsion-based methods, non-spherical droplets are also not favored because interfacial tension between the two immiscible phases favors spherical droplets, which have the smallest surface area for a given volume. Recent advances in microfluidic technologies enable high degree of control in droplet generation, and ease in tuning the device geometry; this offer a new opportunity to fabricate double emulsion with controlled morphology, which serve as templates for fabricating the nonspherical multi-compartment polymersomes. However, such investigations have not, as yet, been carried out. In this work, we demonstrate the generation of non-spherical polymersomes with multiple compartments. We use glass capillary microfluidics to prepare W/O/W double emulsions with different number of inner aqueous drops. These emulsions are initially stabilized by the amphiphilic diblock copolymers in the oil shells, which consist of a mixture of a volatile good solvent and a less volatile poor solvent for the copolymers. As the good solvent evaporates, the copolymers at the W/O and the O/W interfaces are attracted towards each other to form the membranes. As a result, neighboring inner droplets adhere to one another; this leads to formation of multi-compartment polymersomes, as schematically illustrated in Scheme 1. We also use a modified glass capillary device for generating double emulsions with two distinct inner phases containing different encapsulants; this process leads to the fabrication of non-spherical polymersomes with multiple compartments for separate encapsulation of multiple actives. A glass capillary microfluidic device is used to generate double emulsions with controlled morphology. (See Fig. S1 in Supporting Information) Due to the high degree of control afforded by microfluidics, the number of inner droplets in a W/O/W double emulsion system can be controlled by varying the flow rates of the three phases independently; 12] an example of the process is shown in Fig. 1A. The thickness of the double emulsion shells can be adjusted by changing the flow rates; however, as long as the flow rates are not altered enough to change the number of inner droplets of the double emulsion templates, change in shell thickness does not affect the morphology of the final polymersomes since all solvents in the shells is removed in subsequent steps. To prepare the double emulsion templates, multiple inner droplets are dispersed in drops of a mixture of chloroform and hexanes (36:65 v/v) with 10 mg/mL poly(ethylene-glycol)-b-poly(lactic acid), (PEG(5000)-bPLA(5000)); the drops-in-drops are suspended and stabilized in a poly(vinyl alcohol) (PVA) solution. A homopolymer, PEG, is added [] Prof. D. A. Weitz, Dr. H. C. Shum, Dr. S. H. Kim School of Engineering and Applied Sciences, Department of Physics and Kavli Institute for Bionano Science and Technology, Harvard University, Cambridge, Massachusetts 02138 (USA) Fax: (+1) 617-495-0426 E-mail: weitz@seas.harvard.edu Homepage: http://www.seas.harvard.edu/projects/weitzlab/

Shin-Hyun Kim

Papers

Self-assembled colloidal structures for photonics

Characterizing and tracking single colloidal particles with video holographic microscopy

Synthesis and assembly of structured colloidal particles

Colloidal Photonic Crystals toward Structural Color Palettes for Security Materials

Multicompartment polymersomes from double emulsions