Programming biomolecular self-assembly pathways

In nature, self-assembling and disassembling complexes of proteins and nucleic acids bound to a variety of ligands perform intricate and diverse dynamic functions. In contrast, attempts to rationally encode structure and function into synthetic amino acid and nucleic acid sequences have largely focused on engineering molecules that self-assemble into prescribed target structures, rather than on engineering transient system dynamics. To design systems that perform dynamic functions without human intervention, it is necessary to encode within the biopolymer sequences the reaction pathways by which self-assembly occurs. Nucleic acids show promise as a design medium for engineering dynamic functions, including catalytic hybridization, triggered self-assembly and molecular computation. Here, we program diverse molecular self-assembly and disassembly pathways using a 'reaction graph' abstraction to specify complementarity relationships between modular domains in a versatile DNA hairpin motif. Molecular programs are executed for a variety of dynamic functions: catalytic formation of branched junctions, autocatalytic duplex formation by a cross-catalytic circuit, nucleated dendritic growth of a binary molecular 'tree', and autonomous locomotion of a bipedal walker.     

Tween-modified suspension array for sensitive biomolecular detection

Suspension arrays are attracting increasing interest for detecting and quantifying proteins, nucleic acids and other biomolecules. Among various suspension arrays, sillica-based suspension arrays which benefit from low fluorescence background and material stability have been widely used. Sillica-based suspension arrays are often manufactured with the popular aldehyde-aminosilane chemistry for the attachment of a variety of biomolecules. One drawback of this immobilization strategies is the relatively high array particles lost efficiency when washed by centrifugation. Due to this shortcoming, it is low reproductivity and limited in multiplex assay. Herein we report a novel method to fabricate Tween-coated suspension sillica particles, which could achieve good- reproductivity and the low limit of detection. Tween surfactants, each containing hydrophilic ethylene glycol head groups and a hydrophobic alkyl tail, prevent silica particles from being adsorbed onto the centrifuge tube wall and make beads resuspended well. Also, Tween with low fluorescence background could reduce non-specific protein adsorption. Also Tween surfactants are economic and facile agent. In this study, we demonstrate the preparation of the protein array to substantiate the applicability of our approach. Under the optimized experiment conditions, the limit of detection of our Tween-modified particles is as low as 50 pg/mL, which is sufficiently low for the current methods. We believe that the proposed method could provide a perspective on the improvement of self-encoded silica particle arrays.     

对语言起源的探索

语言的起源，历来是人们比较关注的问题，这里结合古今中外历史学，人类学和现代科学的理论，对语言起源的发展过程进行了初步的探索     

幼虫的起源

长期以来，幼虫和成虫是由同一基因物种进化而来这一假设与许多生物学现象有着难以调和的矛盾。本书的作者提出了一个大胆的猜想——决定幼虫形态的相关基因可能是由不同种类动物交互移植而来，并通过举例论证了这一幼虫基因移植论的可行性。     

Potential for biomolecular imaging with femtosecond X-ray pulses

Sample damage by X-rays and other radiation limits the resolution of structural studies on non-repetitive and non-reproducible structures such as individual biomolecules or cells. Cooling can slow sample deterioration, but cannot eliminate damage-induced sample movement during the time needed for conventional measurements. Analyses of the dynamics of damage formation suggest that the conventional damage barrier (about 200 X-ray photons per A2 with X-rays of 12 keV energy or 1 A wavelength) may be extended at very high dose rates and very short exposure times. Here we have used computer simulations to investigate the structural information that can be recovered from the scattering of intense femtosecond X-ray pulses by single protein molecules and small assemblies. Estimations of radiation damage as a function of photon energy, pulse length, integrated pulse intensity and sample size show that experiments using very high X-ray dose rates and ultrashort exposures may provide useful structural information before radiation damage destroys the sample. We predict that such ultrashort, high-intensity X-ray pulses from free-electron lasers that are currently under development, in combination with container-free sample handling methods based on spraying techniques, will provide a new approach to structural determinations with X-rays.     

台湾民族文化的源流初探

从台湾文化最初的源头开始,以大量的事实证明,台湾最早的居民是由东山陆桥到台湾的古越人。台湾原住民的民族文化就是古越人的文化,这在台湾考古文物和民俗文化中都得到了充分的证据。对于认为台湾原住民文化来自南岛的观点,也进行了分析,指出南岛文化的历史远比台湾雅美人等原住民的历史为短。台湾原住民的语言和文化,同大洋洲波利尼西亚居民的语言和文化有相似之处,是由于他们都是古越人的后裔,台湾也可能是古越人去南岛的中间站。当然,台湾有些民族是从南岛迁徙回来的,那已经是很晚的事情。故而台湾最原始的文化源头是在祖国大陆,这是众多人类学家、历史学家、考古学家、民俗学家、文化学家们公认的事实。     

“起源”的科学追问

<正>一些科学研究话题,注定要永远缠绕人类的神经,就像人与世界的"起源"问题。近50年来,"宇宙大爆炸"已成为最主流、最为广泛接受的宇宙生成模型理论,如今我们所谓的"宇宙"被描述为起源于大约137亿年前的一次大爆炸。现在宇宙物理学的几乎所有研究都与宇宙大爆     

Determination of the absolute handedness of knots and catenanes of DNA

DNA winds about itself in a right-handed or left-handed fashion at several structural levels. The double helix is generally right-handed and is given a (+) sign by convention, whereas supercoiling of the helix axis is always (-) in the cell. The winding in higher -order forms such as knots and catenanes is unknown, and this has impeded elucidation of the mechanisms of their formation and resolution by replication, recombination and topoisomerase action. We introduce here a procedure for determining the handedness of DNA winding by inspection of electron micrographs of DNA molecules coated with Escherichia coli RecA protein. We demonstrate the validity of the method and show that DNA topoisomerase I of E. coli generates an equal mixture of (+) and (-) duplex DNA knots, and that one product of recombination by resolvase of transposon Tn3 (refs 8, 9) is a catenane of uniquely (+) sign.     

浅析部分四川方言词语的民俗语源

本文分析了部分四川方言词语的民俗语源 ,并认为探究方言词语的语源 ,绝不应只拘泥于语言的内容研究 ,还应该结合其产生的一些文化背景     

Origins of major human infectious diseases

Many of the major human infectious diseases, including some now confined to humans and absent from animals, are 'new' ones that arose only after the origins of agriculture. Where did they come from? Why are they overwhelmingly of Old World origins? Here we show that answers to these questions are different for tropical and temperate diseases; for instance, in the relative importance of domestic animals and wild primates as sources. We identify five intermediate stages through which a pathogen exclusively infecting animals may become transformed into a pathogen exclusively infecting humans. We propose an initiative to resolve disputed origins of major diseases, and a global early warning system to monitor pathogens infecting individuals exposed to wild animals.     

论英语语法模糊性的哲学根源

语法是人类对纷繁复杂语言现象的抽象化和模块化,即范畴化。然而,由于客观事物的连续性、多样性和多变性,人类的思维在认识世界和借助语言对世界进行范畴化的过程中都发挥着积极主动的作用,语法范畴与概念范畴间必然存在差异性,因而导致了语法范畴的模糊性。