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

Energy harvested directly from sunlight offers a desirable approach toward fulfilling, with minimal environmental impact, the need for clean energy. Solar energy is a decentralized and inexhaustible natural resource, with the magnitude of the available solar power striking the earth’s surface at any one instant equal to 130 million 500 MW power plants.1 However, several important goals need to be met to fully utilize solar energy for the global energy demand. First, the means for solar energy conversion, storage, and distribution should be environmentally benign, i.e. protecting ecosystems instead of steadily weakening them. The next important goal is to provide a stable, constant energy flux. Due to the daily and seasonal variability in renewable energy sources such as sunlight, energy harvested from the sun needs to be efficiently converted into chemical fuel that can be stored, transported, and used upon demand. The biggest challenge is whether or not these goals can be met in a costeffective way on the terawatt scale.2

http://pubs.acs.org/doi/pdf/10.1021/cr1002326

Solar Water Splitting Cells

Objective evaluation of the activity of electrocatalysts for water oxidation is of fundamental importance for the development of promising energy conversion technologies including integrated solar water-splitting devices, water electrolyzers, and Li-air batteries. However, current methods employed to evaluate oxygen-evolving catalysts are not standardized, making it difficult to compare the activity and stability of these materials. We report a protocol for evaluating the activity, stability, and Faradaic efficiency of electrodeposited oxygen-evolving electrocatalysts. In particular, we focus on methods for determining electrochemically active surface area and measuring electrocatalytic activity and stability under conditions relevant to an integrated solar water-splitting device. Our primary figure of merit is the overpotential required to achieve a current density of 10 mA cm–2 per geometric area, approximately the current density expected for a 10% efficient solar-to-fuels conversion device. Utilizing ...

Benchmarking Heterogeneous Electrocatalysts for the Oxygen Evolution Reaction

A fundamental change has been achieved in understanding surface electrochemistry due to the profound knowledge of the nature of electrocatalytic processes accumulated over the past several decades and to the recent technological advances in spectroscopy and high resolution imaging. Nowadays one can preferably design electrocatalysts based on the deep theoretical knowledge of electronic structures, via computer-guided engineering of the surface and (electro)chemical properties of materials, followed by the synthesis of practical materials with high performance for specific reactions. This review provides insights into both theoretical and experimental electrochemistry toward a better understanding of a series of key clean energy conversion reactions including oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). The emphasis of this review is on the origin of the electrocatalytic activity of nanostructured catalysts toward the aforementioned reactions by correlating the apparent electrode performance with their intrinsic electrochemical properties. Also, a rational design of electrocatalysts is proposed starting from the most fundamental aspects of the electronic structure engineering to a more practical level of nanotechnological fabrication.

Design of electrocatalysts for oxygen- and hydrogen-involving energy conversion reactions

Chemically derived graphene oxide (GO) is an atomically thin sheet of graphite that has traditionally served as a precursor for graphene, but is increasingly attracting chemists for its own characteristics. It is covalently decorated with oxygen-containing functional groups - either on the basal plane or at the edges - so that it contains a mixture of sp(2)- and sp(3)-hybridized carbon atoms. In particular, manipulation of the size, shape and relative fraction of the sp(2)-hybridized domains of GO by reduction chemistry provides opportunities for tailoring its optoelectronic properties. For example, as-synthesized GO is insulating but controlled deoxidation leads to an electrically and optically active material that is transparent and conducting. Furthermore, in contrast to pure graphene, GO is fluorescent over a broad range of wavelengths, owing to its heterogeneous electronic structure. In this Review, we highlight the recent advances in optical properties of chemically derived GO, as well as new physical and biological applications.

/pdf/graphene-oxide-as-a-chemically-tunable-platform-for-optical-2c6i758087.pdf

Graphene oxide as a chemically tunable platform for optical applications

The collisions of single platinum nanoparticles at an ultramicroelectrode were observed electrochemically by their characteristic current−time transients for a particle-catalyzed reaction. A single event is characterized by the current generated by an electrocatalyzed reaction of an indicator species (proton, hydrogen peroxide) present in solution. Since the indicator reaction does not occur at the selected ultramicroelectrode and can involve a high concentration of indicator species with a much larger diffusion coefficient than the nanoparticle, large amplification (10 orders of magnitude or more) in the current occurs. Every collision produces a unique current−time profile that can be correlated with the particle size, the particle residence time, and the nature of the particle interaction with the electrode surface. Applications to studying heterogeneous kinetics at single nanoparticles, determining particle size distributions, and as a very sensitive electroanalytical technique are suggested.

/pdf/observing-single-nanoparticle-collisions-at-an-3adj20c2jc.pdf

Observing single nanoparticle collisions at an ultramicroelectrode by electrocatalytic amplification.

Electrochemical hydrazine oxidation and proton reduction occur at a significantly higher rate at Pt than at Au or C electrodes. Thus, the collision and adhesion of a Pt particle on a less active Au or C electrode leads to a large current amplification by electrocatalysis at single nanoparticles (NPs). At low particle concentrations, the collision of Pt NPs was characterized by current transients composed of individual current profiles that rapidly attained a steady state, signaling single NP collisions. The characteristic steady-state current was used to estimate the particle size. The fluctuation in collision frequency with time indicates that the collision of NPs at the detector electrodes occurs in a statistically random manner, with the average frequency a function of particle concentration and diffusion coefficient. A longer term current decay in single current transients, as opposed to the expected steady-state behavior, was more pronounced for proton reduction than for hydrazine oxidation, revealing microscopic details of the nature of the particle interaction with the detector electrode and the kinetics of electrocatalysis at single NPs. The study of single NP collisions allows one to screen particle size distributions and estimate NP concentrations and diffusion coefficients.

/pdf/current-transients-in-single-nanoparticle-collision-events-51absi0xnp.pdf

Current transients in single nanoparticle collision events.

This paper offers a perspective on inner-sphere heterogeneous electron-transfer reactions and electrocatalysis as it is applied to electrochemical energy conversion systems. Fundamental concepts and an overview of past approaches to studies of these types of reactions are discussed. A method for the discovery of new electrocatalysts (for example, ones for the oxygen reduction reaction) and photocatalysts (for solar energy conversion to fuels) based on scanning electrochemical microscopy is briefly described, as well as new surface interrogation techniques for quantifying intermediates.

/pdf/inner-sphere-heterogeneous-electrode-reactions-wotgqv1ltl.pdf

Inner-Sphere Heterogeneous Electrode Reactions. Electrocatalysis and Photocatalysis: The Challenge

Journal of the American Chemical Society is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Polymer films on electrodes. 5. Electrochemistry and chemiluminescence at Nafion-coated electrodes Israel Rubinstein, and Allen J. Bard J. Am. Chem. Soc., 1981, 103 (17), 5007-5013• DOI: 10.1021/ja00407a006 • Publication Date (Web): 01 May 2002 Downloaded from http://pubs.acs.org on February 13, 2009

Polymer Films on Electrodes. 5. Electrochemistry and Chemiluminescence at Nafion-Coated Electrodes

The identity of charges generated by contact electrification on dielectrics has remained unknown for centuries and the precise determination of the charge density is also a long-standing challenge. Here, electrostatic charges on Teflon (polytetrafluoroethylene) produced by rubbing with Lucite (polymethylmethacrylate) were directly identified as electrons rather than ions by electrochemical (redox) experiments with charged Teflon used as a single electrode in solution causing various chemical reactions: pH increases; hydrogen formation; metal deposition; Fe(CN)(6)(3-) reduction; and chemiluminescence in the system of Teflon(-)/Ru(bpy)(3)(2+)/S(2)O(8)(2-) (analogous to electrogenerated chemiluminescence). Moreover, copper deposition could be amplified by depositing Pd first in a predetermined pattern, followed by electroless deposition to produce Cu lines. This process could be potentially important for microelectronic and other applications because Teflon has desirable properties including a low dielectric constant and good thermal stability. Charge density was determined using Faraday's law and the significance of electron transfer processes on charged polymers and potentially other insulators have been demonstrated.

/pdf/electrostatic-electrochemistry-at-insulators-49i08j7v7p.pdf

Allen J. Bard

Papers

Observing single nanoparticle collisions at an ultramicroelectrode by electrocatalytic amplification.

Current transients in single nanoparticle collision events.

Inner-Sphere Heterogeneous Electrode Reactions. Electrocatalysis and Photocatalysis: The Challenge

Polymer Films on Electrodes. 5. Electrochemistry and Chemiluminescence at Nafion-Coated Electrodes

Electrostatic electrochemistry at insulators.