Switchable DNA-origami nanostructures that respond to their environment and their applications

Structural DNA nanotechnology, in which Watson-Crick base pairing drives the formation of self-assembling nanostructures, has rapidly expanded in complexity and functionality since its inception in 1981. DNA nanostructures can now be made in arbitrary three-dimensional shapes and used to scaffold many other functional molecules such as proteins, metallic nanoparticles, polymers, fluorescent dyes and small molecules. In parallel, the field of dynamic DNA nanotechnology has built DNA circuits, motors and switches. More recently, these two areas have begun to merge—to produce switchable DNA nanostructures, which change state in response to their environment. In this review, we summarise switchable DNA nanostructures into two major classes based on response type: molecular actuation triggered by local chemical changes such as pH or concentration and external actuation driven by light, electric or magnetic fields. While molecular actuation has been well explored, external actuation of DNA nanostructures is a relatively new area that allows for the remote control of nanoscale devices. We discuss recent applications for DNA nanostructures where switching is used to perform specific functions—such as opening a capsule to deliver a molecular payload to a target cell. We then discuss challenges and future directions towards achieving synthetic nanomachines with complexity on the level of the protein machinery in living cells.     

Vaults bind directly to microtubules via their caps and not their barrels

Vaults are large (13 Mda) ribonucleoprotein particles that are especially abundant in multidrug resistant cancer cells and have been implicated in nucleocytoplasmic drug transport. To understand how these large barrel-shaped complexes are transported through the cytosol, we examined the association of vaults with microtubules both in vitro and in vivo. Within cells, a subpopulation of vaults clearly associates with microtubules, and these vaults remain associated with tubulin dimers/oligomers when microtubules are disassembled by nocodazole treatment. In vitro, a microtubule-pull down assay using highly purified rat vaults and reassembled microtubules reveals that vaults exhibit concentration-dependent binding to microtubules that does not require the carboxyl terminal end of tubulin. Remarkably, negative staining for electron microscopy reveals that vault binding to microtubules is mediated by the vault caps; more than 82% of bound vaults attach to the microtubule lattice with their long axes perpendicular to the long axis of the microtubule. Five to six vault particles were bound per micron of microtubule, with no crosslinking of microtubules observed, suggesting that only one end of the vault can bind microtubules. Taken together, the data support the model of vaults as barrel-shaped containers that transiently interact with microtubules.     

Epiphytes and their contribution to canopy diversity

About ten percent of all vascular plant species world-wide are epiphytes and they are almost exclusively found in tropical forests. Therefore, they constitute a large part of the global plant biodiversity (10% of all species), and in tropical countries represent up to 25% of all vascular plant species. Focusing on the differences between epiphytes in the strict sense or holo-epiphytes (non-parasitic plants that use other plants – usually trees – as growing sites all through their life-cycle) and hemi-epiphytes (half epiphytes which only spend part of their life as epiphytes until their aerial roots become connected to the ground), horizontal and vertical distribution patterns of both in relation to some of their ecological requirements are compared. Vertical ecological gradients (i.e., insolation and humidity differences from the forest floor to the canopy surface) are relevant for the composition of the holo- epiphytic vegetation. For hemi-epiphytes, however, ecological differences between distinct forest habitats (i.e., horizontal gradients) are relevant, but not primarily the canopy structure, as the individual host tree structure is more important. The scale-dependence of epiphyte diversity assessment (relatively small study areas for holo-epiphytes, large study areas for hemi-epiphytes) is mainly due to the striking differences in plant sizes and related mechanical and physiological requirements.     

生物样本库及其伦理问题简介

随着分子和基因组信息对流行病学影响的增加,无数遗传流行病学研究和后人类基因组计划的研究都越来越依赖人类生物样本库的使用。生物样本库的范围也已横跨学术或者医院环境下的小数量收集到大规模的全国性储藏。尽管生物样本库的概念并不新,但是在基因组研究和后人类基因组计划的背景下,伴随它们十几年极大发展的是无数待解决的伦理挑战。从生物样本库的概念着手,介绍了其与一般遗传数据库的区别以及建立生物样本库的意义;然后介绍并比较国际上已有的生物样本库,以及其伦理问题和伦理法律框架的发展趋势。     

Protandry models and their application to salmon

Mating systems characterized by restricted breeding seasons,male polygamy, and female monogamy are common among animals.In such systems (e.g., butterflies), the earlier emergenceof males than females to breeding areas (protandry) is a typicalphenological pattern. Protandry likely results from a timingstrategy that maximizes mating opportunities by males. In Pacific salmon (Oncorhynchus spp.), males typically arrive at the spawning grounds in advance of females. Using arrival-timing models,I found that under the mate-opportunity hypothesis, the matingsystem of salmon favors protandry. Protandry is predicted undera range of competitive scenarios, and the degree of protandryis especially sensitive to the duration of male spawning activity.Greater protandry is expected with increasing population sexratio (i.e., more males) when there is mate guarding, but lowerprotandry is expected with increasing population sex ratiowhen interference competition among males reduces male longevity.The timing of unequal competitors is expected to be similar,but among years, protandry may be less variable in the bettercompetitor.     

Introduction to beetle luciferases and their applications

All beetle luciferases have evolved from a common ancestor: they all use ATP, O₂, and a common luciferin as substrates. The most studied of these luciferases is that derived from the firefly Photinus pyralis, a beetle in the superfamily of Cantharoidea. The sensitivity with which the activity of this enzyme can be assayed has made it useful in the measurement of minute concentrations of ATP. With the cloning of the cDNA coding this luciferase, it has also found wide application in molecular biology as a reporter gene. We have recently cloned other cDNAs that code for luciferases from the bioluminescent click beetle, Pyrophorus plagiophthalamus, in the superfamily Elateroidea. These newly acquired luciferases are of at least four different types, distinguishable by their ability to emit different colours of bioluminescence ranging from green to orange. Unique properties of these luciferases, especially their emission of multiple colours, may make them additionally useful in applications.     

表观遗传学的相关概念和研究进展

表观遗传学是研究没有DNA序列变化并且可以遗传的基因功能变化之学科,就其中的X染色体刑量补偿、DNA甲基化、组蛋白密码、基因组印记、表观基因组学和人类表观基因组计划等等方面的问题进行了综述。     

Plant molybdoenzymes and their response to stress

Molybdenum-containing enzymes catalyse basic reactions in the nitrogen, sulphur and carbon metabolism. Mo-enzymes contain at their catalytic sites an organometallic structure termed the molybdenum cofactor or Moco. In higher plants, Moco is incorporated into the apoproteins of four enzymes: nitrate reductase (EC 1.6.6.1-3; NR), xanthine dehydrogenase (EC 1.1.1.204; XDH), aldehyde oxidase (EC 1.2.3.1; AO) and sulphite oxidase (EC1.8.3.1; SO). Molybdoenzymes in plants are key enzymes in nitrate assimilation, purine metabolism, hormone biosynthesis, and most probably in sulphite detoxification. They are considered to be involved in stress acclimation processes and, therefore, elucidation of the mechanisms of their response to environmental stress conditions is of agricultural importance for the improvement of plant stress tolerance. Here we would like to give a brief functional and biochemical characteristic of the four plant molybdoenzymes and to focus mainly on their sensitivity to environmental stress factors.     

Honeybees change their height to restore their optic flow

To further elucidate the mechanisms underlying insects’ height and speed control, we trained outdoor honeybees to fly along a high-roofed tunnel, part of which was equipped with a moving floor. Honeybees followed the stationary part of the floor at a given height. On encountering the moving part of the floor, which moved in the same direction as their flight, honeybees descended and flew at a lower height, thus gradually restoring their ventral optic flow (OF) to a similar value to that they had percieved when flying over the stationary part of the floor. This was therefore achieved not by increasing their airspeed, but by lowering their height of flight. These results can be accounted for by a control system called an optic flow regulator, as proposed in previous studies. This visuo-motor control scheme explains how honeybees can navigate safely along tunnels on the sole basis of OF measurements, without any need to measure either their speed or the clearance from the surrounding walls.     

Extracellular vesicles: exosomes,microparticles, their parts,and their targets to enable their biomanufacturing and clinical applications

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Orangutans modify their gestural signaling according to their audience's comprehension

When people are not fully understood, they persist with attempts to communicate, elaborating their speech in order to better convey their meaning [1]. We investigated whether captive orangutans (Pongo pygmaeus and Pongo abelii) would use analogous communicative strategies in signaling to a human experimenter, and whether they could distinguish different degrees of misunderstanding. Orangutans' behavior varied according to how well they had apparently been understood. When their aims were not met, they persisted in communicative attempts. However, when the interlocutor appeared partially to understand their meaning, orangutans narrowed down their range of signals, focusing on gestures already used and repeating them frequently. In contrast, when completely misunderstood, orangutans elaborated their range of gestures, avoiding repetition of failed signals. It is therefore possible, from communicative signals alone, to determine how well an orangutan's intended goal has been met. This differentiation might function under natural conditions to allow an orangutan's intended goals to be understood more efficiently. In the absence of conventional labels, communicating the fact that an intention has been somewhat misunderstood is an important way to establish shared meaning.     

In vivo immunosuppression by pan-T cell antibodies relates to their isotype and to their C1q uptake

There is considerable interest in the use of monoclonal anti-T cell antibodies for immunosuppression during organ transplantation. However, the in vitro cytotoxic titers of these monoclonal reagents do not correlate with their immunosuppressive potency when injected in vivo. A relationship nevertheless seems to exist between immunosuppression and the isotype of anti-mouse Thy-1 antibodies, because among several anti-Thy-1 antibodies of mouse and rat origin, the only two found to cause immunosuppression in vivo belonged to the rat IgG2b and mouse IgG2a isotype. We show here that a quantitative positive correlation exists between an antibody-induced humoral effector mechanism and immunosuppression. We measured the uptake of the C1q complement subunit by polyclonal rabbit and rat anti-thymocyte globulin and also seven monoclonal anti-Thy-1 antibodies in an immunohistochemical assay or a radioimmunoassay. Immunosuppression was studied in a murine graft-vs-host and skin allograft model. Our results suggest strongly that a stable association between the C1 protein and a potential binding antibody is an essential prerequisite of antibody-dependent cell inhibition in vivo that suppresses the immunoresponse against strongly incompatible transplantation antigens.