Configuration-dependent diffusion can shift the kinetic transition state and barrier height of protein folding

We show that diffusion can play an important role in protein-folding kinetics. We explicitly calculate the diffusion coefficient of protein folding in a lattice model. We found that diffusion typically is configuration- or reaction coordinate-dependent. The diffusion coefficient is found to be decreasing with respect to the progression of folding toward the native state, which is caused by the collapse to a compact state constraining the configurational space for exploration. The configuration- or position-dependent diffusion coefficient has a significant contribution to the kinetics in addition to the thermodynamic free-energy barrier. It effectively changes (increases in this case) the kinetic barrier height as well as the position of the corresponding transition state and therefore modifies the folding kinetic rates as well as the kinetic routes. The resulting folding time, by considering both kinetic diffusion and the thermodynamic folding free-energy profile, thus is slower than the estimation from the thermodynamic free-energy barrier with constant diffusion but is consistent with the results from kinetic simulations. The configuration- or coordinate-dependent diffusion is especially important with respect to fast folding, when there is a small or no free-energy barrier and kinetics is controlled by diffusion.Including the configurational dependence will challenge the transition state theory of protein folding.

Novel prefractionation method can be used in proteomic analysis

For the first time, a novel prefractionation method used in proteomic analysis was developed, which is performed by a novel aqueous two-phase system (NATPS) composed of n-butanol, (NH4)(2)SO4, and water. It can separate proteomic proteins into multigroups by one-step extraction. The phase-separation conditions of n-butanol solutions were studied in the presence of commonly used inorganic salts. The NATPS was subsequently developed. Using human serum albumin, zein, and gamma-globulin as model proteins, the separation effectiveness of the NATPS for protein was studied under affection factors, i.e., pH, n-butanol volume, protein, or salt concentration. The model and actual protein samples were separated by the NATPS and then directly used for gel electrophoresis without separating the target proteins from phase-forming reagents. It revealed that the NATPS could separate proteomic proteins into multigroups by one-step extraction. The NATPS has the advantages of rapidity, simplicity, low cost, biocompability, and high efficiency. It need not separate target proteins from the phase-forming reagents. The NATPS has great significance in separation and extraction of proteomic proteins, as well as in methodology.

Pt nanoparticles: Heat treatment-based preparation and Ru(bpy)(3)(2+)-mediated formation of aggregates that can form stable films on bare solid electrode surfaces for solid-state electrochemiluminescence detection

A simple thermal process for the preparation of small Pt nanoparticles is presented, carried out by heating a H-2-PtCl6/3- thiophenemalonic acid aqueous solution. The following treatment of such colloidal Pt solution with Ru( bpy)(3)(2+) causes the assembly of Pt nanoparticles into aggregates. Most importantly, directly placing such aggregates on bare solid electrode surfaces can produce very stable films exhibiting excellent electrochemiluminescence behaviors.

Proteomic detection of changes in protein expression induced by cordycepin in human hepatocellular carcinoma BEL-7402 cells

The nucleoside analogue cordycepin (3'-deoxyodenosine, 3'-dA), one of the components of cordyceps militaris, has been shown to inhibit the growth of various tumor cells. However, the probable mechanism is still obscure. In this study, the inhibition of cell growth and changes in protein expression induced by cordycepin were investigated in BEL-7402 cells. Using the MTT assay and flow cytometry, we found that cordycepin inhibits cell viability and induces apoptosis in BEL 7402 cells. Additionally. the proteins were separated using two-dimensional polyacrylamide gel electrophoresis, and eight proteins were found to be significantly, affected by cordycepin compared to untreated control; among them, two were downregulated and six were upregulated. Of the eight proteins, six were identified with peptide mass fingerprinting using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) after in-gel trypsin digestion. These proteins are involved in various aspects of cellular metabolism. It is suggested that the effect of cordycepin on the growth of tumor cells is significantly related to the metabolism-associated protein expression induced by cordycepin. Copyright 2008 Prous Science, S.A.U. or its licensors. All rights reserved.

Rhein induces apoptosis and cell cycle arrest in human hepatocellular carcinoma BEL-7402 cells

Rhein, an anthraquinone derivative of rhubarb, inhibits the proliferation of various human cancer cells. In this paper, we focused on studying the effects of rhein on human hepatocelluar carcinoma BEL-7402 cells and further understanding the underlying molecular mechanism in an effort to make the potential development of rhein in the treatment of cancers. Using MTT assay and flow cytometry, we demonstrate a critical role of rhein in the suppression of BEL-7402 cell proliferation in a concentration- and time-dependent manner. The increase of apoptosis rate was observed after incubation of BEL-7402 cells with rhein at 50-200 mu M for 48 hours, and the cells exhibit typical apoptotic features including cellular morphological change and chromatin condensation. Moreover, rhein-induced cell cycle S-phase arrest. Additionally, after rhein treatment, expression levels of c-Myc gene were decreased, while those of caspase-3 gene were increased in a dose-dependent manner by using real-time PCR assay. The results demonstrate for the first time that cell cycle S-phase arrest is one of the mechanisms of rhein in inhibition of BEL-7402 cells. Rhein plays its role by inducing cell cycle arrest via downregulation of oncogene c-Myc and apoptosis through the caspase-dependent pathway. It is expected that rhein will be effective and useful as a new agent in hepatocelluar carcinoma treatment in the future.

基于CAN总线的机器人示教盒通讯系统的设计

研发了基于CAN总线的新型机器人示教盒系统,采用ARM芯片为核心,并在其上运行了实时操作系统μC/OS-II。设计了一套CAN网络通讯协议,实现了一个示教盒同时示教多台机器人的一对多示教模式,在很大程度上改进和提高了机器人示教盒的性能。

基于CAN的工业机器人内部通信总线设计

介绍了一种基于CAN总线的分布式工业机器人控制器的研究开发情况,实现了总线与各模块的接口设计,并制定出相应的机器人控制器内部通信协议。这种机器人控制器布线简单,系统可灵活扩展,有效提高了工业机器人的性能。

基于CAN总线的力传感器与机器人控制器通讯设计

研磨机器人系统中,研磨头与工件的接触力是保证加工精度,进行机器人力控制的一个重要因 素。采用 CAN 通讯可以确保力传感器准确、及时地把力信息传送给控制器进行力控制。本文 给出了6维腕力传感器与机器人控制器通讯的硬件结构,制定了可靠的通讯协议,实现了力信 息的正确读取,为研磨机器人控制系统获得可靠的力信息提供了一种新的解决方案。

基于CAN总线的物流拣选设备的设计

简要介绍了物流的发展现状 ,详细描述了基于CAN总线的物流拣选系统的结构、供电方式和参数设定方法 ,并为系统硬件设计中的电源转换、总线驱动和地址译码等公共电路以及总线控制器、电子标签和指示灯控制器等主要设备提供了设计方案 ,为系统软件设计中的C5 1编译、通信协议、命令类型和程序控制规划等问题给出了相应的解决方法 ,还与进口同类产品的性能和价格进行了比较

基于CAN总线的机器人网络互联

根据工业机器人的应用现状，利用现有的控制技术，结合控制局域网（CAN）技术和通信技术，通过对现有的机器人控制器进行硬件改进和软件开发，并相应开发出上位机监控系统，实现了多台机器人的网络互联，最终实现基于CAN网络的机器人生产线集成系统。

基于CAN总线的全数字伺服驱动系统的研究

本论文以创新课题“家用服务机器人的研究开发”为背景，对全数字电机伺服驱动系统进行了深入的研究，在此基础上提出了伺服驱动系统的总体设计方案，参与了硬件系统各子模块的设计与调试，完成了软件伺服控制，最终实现了基于CAN总线的全数字伺服驱动系统。论文结合开发的上位机测试软件进行了实验研究，取得了比较理想的实验结果。 本文以该系统为平台，对伺服驱动系统中的难点和热点问题进行了研究，针对这些问题，提出了以下系统设计和实现的新方法和新思路： 1. 将数字信号处理器DSP和现场总线CAN应用到伺服驱动系统中，采用CANopen通讯协议进行信息传输，保证了通讯功能的可靠性； 2. 在电机转速测量中，提出了一种高性能的自适应转速测量算法，与常用的算法相比，提出的算法可以在提高转速测量的准确性的同时，提高系统的响应时间； 3. 在电流测量中，应用巴特沃斯滤波器对电流信号进行滤波，以消除电流采样中的干扰，同时使用Smith预估器消除系统延时产生的影响； 4. 在电机控制算法的研究上，引进了参数模糊自整定PI控制器，该方法实现了高品质的动态和静态性能； 5. 将S/T曲线速度规划的思想引入全数字伺服驱动系统中，通过提高速度的平滑性，特别是高速启、制动状态，来提高伺服系统的整体控制性能。针对DSP芯片定点运算的限制，本文提出了一种余码补偿方案。 本论文理论与实际相结合，以自主研发的服务机器人为平台，对提出的方法进行了实验检验，实验的结果表明本文设计的软、硬件结构合理，控制精度高，响应快，可以满足生产使用的需求。

基于CAN总线的多机器人支撑环境的研究与实现

本论文旨在利用现有的机器人控制技术，结合现场总线（CAN）技术和通信技术，通过对现有机器人控制器进行的硬件改进和软件开发，在提高控制器性能的前提下，使其适合于多机器人生产线模式。并结合自行开发的上位机监控制软件，实现多台机器人的网络互联。本论文完成了从总体结构设计到具体实现工作，包括监控机系统软件、机器人控制器实时操作系统软件编制，为多机器人系统提供了强有力的支撑环境，实现了多机器人系统的在线状态查询、监控、作业文件下载和备伤等功能。并为控制器开发出内嵌软PLC，使多机器人生产线系统对自身及周边设备I/O具有了更强的适应能力。

基于CAN的仿人机器人控制器的设计与实现

本文针对仿人机器人的结构和控制性能的要求,设计并实现了基于CAN的关节控制器,并利用CAN把各个关节和力传感器及上位机连接在一起,构成了有效可靠的控制系统。主要包括仿人机器人的总体结构、控制器的硬件与软件的设计实现、控制系统的拓扑结构等,并提出了一些设想以提高系统的性能。

基于CAN总线的分布式数据采集与控制系统

本文给出了一种基于 CAN总线的分布式数据采集与控制系统的设计与应用，介绍了 CAN总线的硬件接口电路设计，并对系统的整体结构、硬件配置、软件功能及各节点功能分别作了详细说明。实验表明，该系统具有结构简单、可靠性高、性能价格比高等特点，有广阔的应用前景。