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

The calculation of rate coefficients is a discipline of nonlinear science of importance to much of physics, chemistry, engineering, and biology. Fifty years after Kramers' seminal paper on thermally activated barrier crossing, the authors report, extend, and interpret much of our current understanding relating to theories of noise-activated escape, for which many of the notable contributions are originating from the communities both of physics and of physical chemistry. Theoretical as well as numerical approaches are discussed for single- and many-dimensional metastable systems (including fields) in gases and condensed phases. The role of many-dimensional transition-state theory is contrasted with Kramers' reaction-rate theory for moderate-to-strong friction; the authors emphasize the physical situation and the close connection between unimolecular rate theory and Kramers' work for weakly damped systems. The rate theory accounting for memory friction is presented, together with a unifying theoretical approach which covers the whole regime of weak-to-moderate-to-strong friction on the same basis (turnover theory). The peculiarities of noise-activated escape in a variety of physically different metastable potential configurations is elucidated in terms of the mean-first-passage-time technique. Moreover, the role and the complexity of escape in driven systems exhibiting possibly multiple, metastable stationary nonequilibrium states is identified. At lower temperatures, quantum tunneling effects start to dominate the rate mechanism. The early quantum approaches as well as the latest quantum versions of Kramers' theory are discussed, thereby providing a description of dissipative escape events at all temperatures. In addition, an attempt is made to discuss prominent experimental work as it relates to Kramers' reaction-rate theory and to indicate the most important areas for future research in theory and experiment.

Reaction-rate theory: fifty years after Kramers

Sensor technology is one of the most important key technologies of the future with a constantly increasing number of applications, both in the industrial and in the private sectors. More and more gas sensors are used for the control of technical processes, in environment monitoring, healthcare, and automobiles. Consequently, the development of fast and sensitive gas sensors with small cross sensitivity is the subject of intense research, propelled by strategies based on nanoscience and -technology. Established systems can be improved and novel sensor concepts based on bottom-up approaches show that the sensor properties can be controlled by molecular design. This Review highlights the recent developments and reflects the impact of nanoscience on sensor technology.

Metal and Metal Oxide Nanoparticles in Chemiresistors: Does the Nanoscale Matter?

Xin Zhou,†,‡ Songyi Lee,† Zhaochao Xu,* and Juyoung Yoon*,† †Department of Chemistry and Nanoscience, Ewha Womans University, Seoul 120-750, Republic of Korea ‡Research Center for Chemical Biology, Department of Chemistry, Yanbian University, Yanjii 133002, People’s Republic of China Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Shahekou, Dalian, Liaoning, People’s Republic of China

Recent Progress on the Development of Chemosensors for Gases.

The article tells about the diversity of green spaces in London, the citizens’ attitude toward these spaces, and what Russian cities can learn from this experience.

Nature in London

Tunneling phenomena in chemical physics

Theory of tunnel transitions of atoms in solids

The conductometric response of SnO 2  + In 2 O 3 nanocomposite films to hydrogen and carbon monoxide in air are investigated experimentally for varying oxide compositions. The fundamental mechanism of sensory phenomena in such nanocomposite films is also discussed. The experimental results indicate that the response ( θ com ) of the sensor is determined by the current flow path in the film. For composites with In 2 O 3 composition ( X In ) less than 20 wt.%, current flows through the SnO 2 crystals. Due to electron transfer from the In 2 O 3 inclusions to the SnO 2 matrix, an increase in X In up to 20 wt.% leads to a significant increase in the conductivity of the composite sensor and θ com for both CO and H 2 . A further increase in X In results in percolation transition for In 2 O 3 nanocrystals, which form conducting clusters (threads) of In 2 O 3 , with electrical conductivity that is much higher than that of SnO 2 . The transition from conduction through the SnO 2 crystals to conduction through the In 2 O 3 crystals in the composite films occurs at X In in the range about 20–50 wt.%. For X In  ≥ 50 wt.%, θ com is entirely determined by the sensory properties of the In 2 O 3 conducting clusters, and electron transfer from In 2 O 3 clusters to SnO 2 results in a decrease of θ com .

Effect of composition on sensing properties of SnO2 + In2O3 mixed nanostructured films

This study reviews the structure and properties of nanostructured composite conductometric sensors based on semiconducting metal oxides, and the physico-chemical processes occurring when applied for detection of ambient reducing gases. It discusses the mechanisms of electronic and chemical sensitization in composites comprised of metal oxides of different electronic and chemical properties. In particular, the relationship between the conductivity mechanisms and sensory effect is examined, considering the transfer of electrons between the oxide components of the composite semiconductor sensor. A separate section is devoted to new systems consisting of composite nanofibers of the core-shell type, the sensory characteristics of which depend on the transfer of electrons between the core and the shell in the nanofiber. It is demonstrated that by changing the nature of the components and their relative locations in such nanofibers, the sensitivity and selectivity of the sensor system can be tailored to various chemical compounds. Thus, the use of composite metal oxide systems can lead to improved efficiency and selectivity of conductometric sensors, and enable the development of sensor systems with the desired operating properties.

Leonid I. Trakhtenberg

Papers

Tunneling phenomena in chemical physics

Theory of tunnel transitions of atoms in solids

Effect of composition on sensing properties of SnO2 + In2O3 mixed nanostructured films

The mechanisms of sensory phenomena in binary metal-oxide nanocomposites

Effect of pressure and temperature on the H-atom tunneling in solid phase chemical reactions. The acridine/fluorene system