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?

Since the discovery of mechanically exfoliated graphene in 2004, research on ultrathin two-dimensional (2D) nanomaterials has grown exponentially in the fields of condensed matter physics, material science, chemistry, and nanotechnology. Highlighting their compelling physical, chemical, electronic, and optical properties, as well as their various potential applications, in this Review, we summarize the state-of-art progress on the ultrathin 2D nanomaterials with a particular emphasis on their recent advances. First, we introduce the unique advances on ultrathin 2D nanomaterials, followed by the description of their composition and crystal structures. The assortments of their synthetic methods are then summarized, including insights on their advantages and limitations, alongside some recommendations on suitable characterization techniques. We also discuss in detail the utilization of these ultrathin 2D nanomaterials for wide ranges of potential applications among the electronics/optoelectronics, electrocat...

Recent Advances in Ultrathin Two-Dimensional Nanomaterials

Graphene oxide: preparation, functionalization, and electrochemical applications.

Human skin is a remarkable organ. It consists of an integrated, stretchable network of sensors that relay information about tactile and thermal stimuli to the brain, allowing us to maneuver within our environment safely and effectively. Interest in large-area networks of electronic devices inspired by human skin is motivated by the promise of creating autonomous intelligent robots and biomimetic prosthetics, among other applications. The development of electronic networks comprised of flexible, stretchable, and robust devices that are compatible with large-area implementation and integrated with multiple functionalities is a testament to the progress in developing an electronic skin (e-skin) akin to human skin. E-skins are already capable of providing augmented performance over their organic counterpart, both in superior spatial resolution and thermal sensitivity. They could be further improved through the incorporation of additional functionalities (e.g., chemical and biological sensing) and desired properties (e.g., biodegradability and self-powering). Continued rapid progress in this area is promising for the development of a fully integrated e-skin in the near future.

25th Anniversary Article: The Evolution of Electronic Skin (E-Skin): A Brief History, Design Considerations, and Recent Progress

Being the newest member of the carbon materials family, graphene possesses many unique physical properties resulting is a wide range of applications. Recently, it was discovered that graphene oxide can effectively adsorb DNA, and at the same time, it can completely quench adsorbed fluorophores. These properties make it possible to prepare DNA-based optical sensors using graphene oxide. While practical analytical applications are being demonstrated, the fundamental understanding of binding between graphene oxide and DNA in solution received relatively less attention. In this work, we report that the adsorption of 12-, 18-, 24-, and 36-mer single-stranded DNA on graphene oxide is affected by several factors. For example, shorter DNAs are adsorbed more rapidly and bind more tightly to the surface of graphene. The adsorption is favored by a lower pH and a higher ionic strength. The presence of organic solvents such as ethanol can either increase or decrease adsorption depending on the ionic strength of the so...

/pdf/adsorption-and-desorption-of-dna-on-graphene-oxide-studied-3dsxl08802.pdf

Adsorption and desorption of DNA on graphene oxide studied by fluorescently labeled oligonucleotides.

Touch (or tactile) sensors are gaining renewed interest as the level of sophistication in the application of minimum invasive surgery and humanoid robots increases. The spatial resolution of current large-area (greater than 1 cm 2 ) tactile sensor lags by more than an order of magnitude compared with the human finger. By using metal and semiconducting nanoparticles, a ∼100-nm-thick, large-area thin-film device is self-assembled such that the change in current density through the film and the electroluminescent light intensity are linearly proportional to the local stress. A stress image is obtained by pressing a copper grid and a United States 1-cent coin on the device and focusing the resulting electroluminescent light directly on the charge-coupled device. Both the lateral and height resolution of texture are comparable to the human finger at similar stress levels of ∼10 kilopascals.

/pdf/high-resolution-thin-film-device-to-sense-texture-by-touch-51ov78ie7o.pdf

High-resolution thin-film device to sense texture by touch.

Interfacing DNA oligonucleotides with graphene-based materials, especially graphene oxide, has produced many new sensors and devices. Since graphene oxide is an excellent fluorescence quencher, fluorescently labeled DNAs (probes) are nearly fully quenched upon adsorption. Addition of the complementary DNA results in probe desorption and fluorescence enhancement. Aside from its analytical applications, this system provides a fascinating topic for biointerface science. DNA can be adsorbed by graphene oxide via π–π stacking and hydrogen bonding, while it must overcome electrostatic repulsion at the same time. The mechanism of DNA-induced probe desorption has also been a topic of extensive discussion. In this article, DNA adsorption and desorption reactions and interactions with graphene oxide and related materials (e.g. graphene) are reviewed based on the current understandings. A few representative applications based on these processes are also described briefly.

DNA adsorbed on graphene and graphene oxide: Fundamental interactions, desorption and applications

Our sense of touch enables us to recognize texture and shape and to grasp objects. The challenge in making an electronic skin which can emulate touch for applications such as a humanoid robot or minimally invasive and remote surgery is both in mimicking the (passive) mechanical properties of the dermis and the characteristics of the sensing mechanism, especially the intrinsic digital nature of neurons. Significant progress has been made towards developing an electronic skin by using a variety of materials and physical concepts, but the challenge of emulating the sense of touch remains. Recently, a nanodevice was developed that has achieved the resolution to decipher touch on a par with the human finger; this resolution is over an order of magnitude improvement on previous devices with a sensing area larger than 1 cm(2). With its robust mechanical properties, this new system represents an important step towards the realization of artificial touch.

Tactile devices to sense touch on a par with a human finger.

Interfacing cells with nanomaterials such as graphene, nanowires, and carbon nanotubes is useful for the integration of cellular physiology with electrical read outs. Here we show the interfacing of graphene sheets on the surface of yeast cells, leading to electromechanical coupling between the sheets and the cells. The cells are viable after the interfacing. The response caused by physiologically stressing the cells by exposure to alcohols, which causes a change in cell volume, can be observed in the electrical signal through graphene. The change in the cell volume leads to straining of the sheets, forming wrinkles which reduce the electrical conductivity. As the dynamic response of the cell can be observed, it is possible to differentiate between ethanol, 2-propanol, and water. We believe this will lead to further development of cell-based electrical devices and sensors.

Vivek Maheshwari

Papers

Adsorption and desorption of DNA on graphene oxide studied by fluorescently labeled oligonucleotides.

High-resolution thin-film device to sense texture by touch.

DNA adsorbed on graphene and graphene oxide: Fundamental interactions, desorption and applications

Tactile devices to sense touch on a par with a human finger.

Graphene as cellular interface: electromechanical coupling with cells.