Mechanically driven ATP synthesis by F1-ATPase

ATP, the main biological energy currency, is synthesized from ADP and inorganic phosphate by ATP synthase in an energy-requiring reaction. The F1 portion of ATP synthase, also known as F1-ATPase, functions as a rotary molecular motor: in vitro its gamma-subunit rotates against the surrounding alpha3beta3 subunits, hydrolysing ATP in three separate catalytic sites on the beta-subunits. It is widely believed that reverse rotation of the gamma-subunit, driven by proton flow through the associated F(o) portion of ATP synthase, leads to ATP synthesis in biological systems. Here we present direct evidence for the chemical synthesis of ATP driven by mechanical energy. We attached a magnetic bead to the gamma-subunit of isolated F1 on a glass surface, and rotated the bead using electrical magnets. Rotation in the appropriate direction resulted in the appearance of ATP in the medium as detected by the luciferase-luciferin reaction. This shows that a vectorial force (torque) working at one particular point on a protein machine can influence a chemical reaction occurring in physically remote catalytic sites, driving the reaction far from equilibrium.     

Java字节码异常处理中信息流的分析

为提高Java移动代码动态安全验证的准确性和实用性,通过分析Java字节码中异常处理的方式与流程,提出了追踪、记录异常处理中信息流的方法.采用字节码改写技术,将异常处理中信息流的相关数据封装在异常类当中,从而保证了所采取的处理对Java虚拟机的透明性,并进一步提高了动态验证的精度.     

Crystal structure of the human centromeric nucleosome containing CENP-A

In eukaryotes, accurate chromosome segregation during mitosis and meiosis is coordinated by kinetochores, which are unique chromosomal sites for microtubule attachment. Centromeres specify the kinetochore formation sites on individual chromosomes, and are epigenetically marked by the assembly of nucleosomes containing the centromere-specific histone H3 variant, CENP-A. Although the underlying mechanism is unclear, centromere inheritance is probably dictated by the architecture of the centromeric nucleosome. Here we report the crystal structure of the human centromeric nucleosome containing CENP-A and its cognate α-satellite DNA derivative (147 base pairs). In the human CENP-A nucleosome, the DNA is wrapped around the histone octamer, consisting of two each of histones H2A, H2B, H4 and CENP-A, in a left-handed orientation. However, unlike the canonical H3 nucleosome, only the central 121 base pairs of the DNA are visible. The thirteen base pairs from both ends of the DNA are invisible in the crystal structure, and the αN helix of CENP-A is shorter than that of H3, which is known to be important for the orientation of the DNA ends in the canonical H3 nucleosome. A structural comparison of the CENP-A and H3 nucleosomes revealed that CENP-A contains two extra amino acid residues (Arg?80 and Gly?81) in the loop 1 region, which is completely exposed to the solvent. Mutations of the CENP-A loop 1 residues reduced CENP-A retention at the centromeres in human cells. Therefore, the CENP-A loop 1 may function in stabilizing the centromeric chromatin containing CENP-A, possibly by providing a binding site for trans-acting factors. The structure provides the first atomic-resolution picture of the centromere-specific nucleosome.     

电吉他增加畸变后的音色研究

声音畸变是电吉他音乐最重要的特性之一，对电吉他增加畸变后的音色的描述是目前的研究热点．笔者利用实验手段研究了不同畸变后得到的音色差别与从震源信号的自相关函数中提取出来的物理因子的关系，并利用自相关函数Φ（0）定义了一个因子WΦ（0）在利用模拟声音畸变进行的实验中，发现形WΦ（0）因子可以较好地描述声音的畸变，同时，音色的差别与WΦ（0）的平均值有较强的相关关系．另一项采用商业化效应器进行的实验也得到了类似的结果，这表明音色差异与WΦ（。0）的均值之间也有强的相关关系．     

用激光多普勒速度计测定瑞利波的声弹性效应

提出了一种利用激光技术非接触测量超声波速度的方法，用该方法测量了铝合金（Al5052)试件的声弹性系数，为了验证其可靠性，对同一试件用接触方法也进行了测量，并对实验结果进行了分析，结果表明，提出的非接触测量方法对提高测量精度是很有效的。     

合成气纯氧高压预混湍流火焰结构研究

为了理解高压下合成气纯氧预混湍流火焰中火焰与流动的耦合作用,利用OH-PLIF激光测量技术开展了高压条件下合成气纯氧预混湍流火焰结构研究,获得了高压下预混湍流火焰前锋面结构,得到了火焰前锋面尺度信息,包括火焰体积、火焰面密度和火焰前锋面尺度,并分析了预混湍流火焰前锋面与湍流尺度和层流火焰尺度的相互作用关系.研究结果表明:高压预混湍流火焰前锋面为褶皱火焰面结构,火焰面为小尺度的尖峰结构和大尺度的树干状结构互相叠加;合成气火焰前锋面结构比甲烷混合气火焰更加精细,尺度更小;合成气预混湍流火焰体积较小,放热区较小,在预混贫燃燃气轮机燃烧室中容易产生燃烧振荡;合成气和甲烷火焰在湍流燃烧速率上表现出不同的转折规律,这可以通过火焰前锋面尺度和火焰自身不稳定性尺度来解释;湍流流动对火焰前锋面的扰动受到火焰自身不稳定尺度的限制.     

Fabrication and characterization of TiO2 -based dye-sensitized solar cells

Dye-sensitized solar cells TiO_2 with were fabricated.The phase composition and microstructures of the solar cells were examined by X-ray diffractometry and transmission electron microscopy,and the energy levels of the present solar cells were also discussed.The results show that a solar cell mixed with xylenol orange and rose Bengal shows a higher conversion efficiency compared to solar cells with a single dye.An introduction of amorphous TiO_2 layers results in an improvement of the conversion efficien...