‘All That Glitters Is Not Gold’: High-Resolution Crystal Structures of Ligand-Protein Complexes Need Not Always Represent Confident Binding Poses

Our understanding of the structure–function relationships of biomolecules and thereby applying it to drug discovery programs are substantially dependent on the availability of the structural information of ligand–protein complexes. However, the correct interpretation of the electron density of a small molecule bound to a crystal structure of a macromolecule is not trivial. Our analysis involving quality assessment of ~0.28 million small molecule–protein binding site pairs derived from crystal structures corresponding to ~66,000 PDB entries indicates that the majority (65%) of the pairs might need little (54%) or no (11%) attention. Out of the remaining 35% of pairs that need attention, 11% of the pairs (including structures with high/moderate resolution) pose serious concerns. Unfortunately, most users of crystal structures lack the training to evaluate the quality of a crystal structure against its experimental data and, in general, rely on the resolution as a ‘gold standard’ quality metric. Our work aims to sensitize the non-crystallographers that resolution, which is a global quality metric, need not be an accurate indicator of local structural quality. In this article, we demonstrate the use of several freely available tools that quantify local structural quality and are easy to use from a non-crystallographer’s perspective. We further propose a few solutions for consideration by the scientific community to promote quality research in structural biology and applied areas.     

液晶微透镜技术研究新进展

液晶微透镜是一种利用电光效应来改变透镜折射率空间分布和微电子技术工艺制作的新型微透镜,是结合了微透镜技术和液晶良好电控特性的新型光学微纳器件。液晶微透镜具有尺寸微小,焦距可调等优点,在微光学系统和微光机电系统中具有广阔的应用前景。简要概述了液晶微透镜的基本原理和几种典型液晶微透镜类型,包括液晶(LC)和聚合物分散液晶(PDLC)透镜的发展,阐述了液晶微透镜的研究现状以及研究发展趋势。     

高精度蓝宝石卧式粘料机设计

针对在蓝宝石晶棒切割成片的过程中由于无法准确控制晶棒端面的晶向,导致晶棒切割成片后晶片精度达不到加工要求的问题,依据布拉格方程和晶体几何学原理,设计出了高精度蓝宝石卧式粘料机。该设备主要分为左右两部分：左侧包括一个轴向转动结构和滑动装置,可对晶棒端面的Y方向进行调节和修正;右侧主要包括一套压紧装置和水平调整机构,对晶棒端面的X方向进行调节。晶向调整好后直接在右侧的X光下进行准确粘接。经试验表明：切出的晶片晶向角度基本上都在正负3分以内,满足要求。     

双螺杆压缩机振动波动原因分析及处理

双螺杆压缩机是某装置的核心设备,振动时常出现波动现象,影响该装置的长周期平稳生产.由于振动波动出现时间的随机性,给波动信号的有效监测带来一定的困难,通过尝试使用在线监测系统,成功监测到振动波动信号,然后结合机组结构、工艺特点等方面进行深入全面的分析,最终诊断出振动波动原因并提出处理措施,处理之后振动波动现象消除.     

基于Fuzzy-PID双加热探空仪湿度传感器加热控制

为了有效解决了探空仪在高空低温环境中遇到的传感器结露、结冰问题,采用双加热湿度传感器自动轮换交替加热来去除传感器污染,提高测量精度.在常温常压下对双加热湿度传感器进行加热实验,得出在额定电压下,传感器上升温度与响应时间的关系曲线,运用扩充响应曲线法求出双加热湿度传感器加热片的加热模型,通过对加热模型的分析,利用Fuzzy-PID进行加热控制,仿真结果表明利用Fuzzy-PID能够满足实际高空探测的要求.     

纯钛空化水喷丸表面强化及空蚀损伤

采用空化水喷丸技术对工业纯钛表面进行强化处理,研究表面强化机理及空蚀过程。通过显微硬度仪、光学显微镜对空化水喷丸后试样的表面硬度、显微组织、表面形貌和表面粗糙度进行分析。结果表明:具有密排六方结构的纯钛经过水喷丸处理后,试样表面强化层有大量的变形孪晶和次生孪晶。试样表面硬度最大可提高118HV0.2,而表面粗糙度Ra仅为2.1μm,这说明空化水喷丸对纯钛表面的强化效果显著,而且表面损伤较小。在30MPa水喷丸压力下,纯钛水喷丸最佳时间为80min,强化效果最好。水喷丸后试样的强化表面可分为A、B和C 3个区域。A区表面空蚀最严重,空蚀坑小而密集,B区和C区因受到二次射流的作用,空蚀坑具有明显的方向性。     

Influence of Bridgman process conditions on microstructure and porosity of single crystal Ni-base superalloy CMSX-4

Abstract

Synchrotron radiation micro-X-ray fluorescence and micro-X-ray diffraction analysis, micro-computed tomography and transmission electron microscopy were used to investigate the microstructure of turbine blades made of a second generation nickel based superalloy CMSX-4 manufactured by investment casting process via Bridgman technique. The dependence of microstructure on process parameters, among others, on the withdrawal rate was analysed. The results set the stage for optimising the microstructure of the blades in terms of their mechanical properties.     

A comparative study of the local heat transfer distributions around various surface mounted obstacles

In many engineering applications, heat transfer enhancement techniques are of vital importance in order to ensure reliable thermal designs of convective heat transfer applications. This study examines experimentally the heat transfer characteristics on the base plate around various surface mounted obstacles. Local convection coefficients are evaluated in the vicinity of each individual protruding body with great spatial resolution using the transient liquid crystal technique. Five different obstacles of constant height-to-hydraulic diameter ratio （-1.3） are consid- ered. These include： a cylinder, a square, a triangle, a diamond and a vortex generator of delta wing shape design. The experiments were carried out over a range of freestream Reynolds numbers, based on the hydraulic diameter of each obstacle, varying from 4,000 to 13,000. The results indicate a negligible effect of the flow speed on the heat transfer topological structure and a considerable effect of the obstacle geometry on the level and distribution of heat transfer enhancement.     

DD6单晶高温合金再结晶形核位置和机制研究

采用压痕变形方法,利用扫描电镜研究了DD6单晶高温合金在不同温度和状态下的再结晶形核位置及形核机理。结果表明,在低于γ′相溶解温度(≤1 220℃)进行热处理,胞状再结晶可以在碳化物、显微疏松、共晶处形核,1 220℃热处理等轴状再结晶可在表面形核,形成表面再结晶层。在1 270℃热处理时除了第二相形核外,再结晶主要在枝晶干上形核,形成了枝晶状再结晶,再结晶形核的主要机制为亚晶聚合形核机制。     

Structural Feature and Electrochemical Performance of h-LiMnBO3 and Its Carbon Coated Material Prepared by Microwave Synthesis

采用微波合成法制备了LiMnBO3及其碳包覆材料LiMnBO3/C。考察了烧结温度和配料比对LiMnBO3结构的影响。利用XRD、SEM、HR-TEM对材料的结构和形貌进行了表征。通过恒电流充/放电性能及交流阻抗测试研究了材料的电化学性能。结果表明,实验所得LiMnBO3具有六方晶体结构(即制得h-LiMnBO3)。750℃烧结温度下,反应25 min,且nLi:nB:nMn=1:1:1时,材料结晶较为完善、晶粒细小、形貌规整。碳包覆后材料充/放电性能及电导率均有提高。LiMnBO3/C的初次放电比容量达到50.3 mAh/g。