学生园地阿伏伽德罗常数与气体常数测定实验的改进

对阿伏伽德罗常数与气体常数测定实验进行了改进:将原实验中测阴极铜片增重改为测阳极铜片的减重;改变电解液的性质,引入EDTA络合铜离子;用相对更环保的锌片代替铜片等。经过反复实验,最终得到了较优化的实验方案。     

基于手持技术的阿伏伽德罗常数测定

借助手持技术通过电镀法和双液原电池法实验测定阿伏伽德罗常数,进而得出一种新的近似测定阿伏伽德罗常数的方法,并作为教材实验的有益补充,帮助学生理解概念,切实感受化学定量实验的魅力。     

“阿伏伽德罗常数”学习困境分析与对策探讨

探索"阿伏伽德罗常数"中"规定"表述背后隐藏的玄机:0.012 kg~(12)C中含有多少原子;"阿伏伽德罗常数"为什么选择~(12)C作为基准;"阿伏伽德罗常数"的数值如何确定等。得出启示,教师对于"规定"表述应当利用学生的原有经验,发挥学生的自主性;挖掘科学史资源,揭示知识的修正性;结合实验过程,突出实验的重要意义。     

摩尔新定义和准确测定的阿伏伽德罗常数

针对2019年国际SI单位新标准的实施,依据文献对阿伏伽德罗常数和摩尔物质量原理进行了简短的历史回顾。着重于摩尔新定义的概念和准确测定阿伏伽德罗常数的描述,突出了原子量精密测量技术、纳米量级精密测量技术以及材料制备和表征技术的发展。相对而言,摩尔新定义更能体现科学方法和科学思维同化学知识的关系,将会对无机化学、分析化学、物理化学等课程教学引起巨大的冲击波,并且会波及到每个化学专业本科生。本文内容可为提高本科生的科研思维和科研素质提供借鉴。     

单分子正则速率常数理论计算的研究

对单分子反应在不对称Eckart位垒隧道校正的基础上,通过计算累积反应几率N(E),而获得微正则速率常数K(E)和正则速率常数K(T).并设计了完整的计算程序,以HCN→CNH(Ⅰ)及FNC→NCF(Ⅱ)反应为例进行了计算.对于反应(Ⅰ)理论计算结果与实验数据一致,反应(Ⅱ)的计算结果与采用国际通用POLYRATE程序计算的k~(CVT/MEPSAG)(T)值相符合.     

单分子微正则系综振动选模反应速率常数的计算

以过渡状态理论为基础，研究了单分子振动选模反应的微正则系综速率常数的计算方法．在计算中考虑了量子力学隧道效应校正及振动对沿IRC运动的耦合作用校正．以反应C＝CH（F）→HC≡CF的氢迁移反应和C＝CF2→FC≡CF的氟迁移反应为例，研究了它们的面外振动选模反应的速率常数．结果表明，这两个反应在低能区有明显的选模性，在高能区选模性减弱．     

单分子微正则系综振动选模反应速率常数的计算

以过渡状态理论为基础，研究了单分子振动选模反应的微正则系综速率常数的计算方法．在计算中考虑了量子力学隧道效应校正及振动对沿IRC运动的耦合作用校正．以反应C＝CH（F）→HC≡CF的氢迁移反应和C＝CF2→FC≡CF的氟迁移反应为例，研究了它们的面外振动选模反应的速率常数．结果表明，这两个反应在低能区有明显的选模性，在高能区选模性减弱．     

生物分子的单分子检测研究

本文评述了生物单分子检测的方法及其在生物大分子结构与功能之间的关系、酶的活性、反应动力学、分子构象、DNA和RNA的转录、蛋白质折叠等生物学重要问题研究上的应用。对生物单分子检测技术这一研究领域的发展趋势作了展望。     

Aerolysin单分子界面的构建及高选择性单分子检测

提出了一种基于Aerolysin膜蛋白质分子构建单分子界面的方法, 运用蛋白质工程技术对单分子界面进行定点修饰, 所建立方法灵活、 可控且重复性好. 采用Poly(dA)₄为探针分子对修饰后的单分子界面进行了表征, 结果表明, 在孔口处的Arginine修饰影响了寡聚核苷酸的选择性. 为进一步理解Aerolysin单分子界面及合理设计功能性单分子界面提供了参考.     

丁酸甲酯单分子解离的非谐振效应

使用MP2/6-311++G（2d,2p）方法和基组,计算了丁酸甲酯单分子解离反应体系详细的势能面。应用RRKM理论,计算了在1000-5000 K的温度范围内的正则系综的速率常数。与此同时,在微正则系综下,我们计算了温度为1000-5000 K对应的能量从451.92到1519.52 kJ·mol^-1的速率常数。计算结果表明反应通道2、4和5的非谐振效应比较明显。因此对于丁酸甲酯单分子解离反应体系来说其非谐振效应是不能忽视的。     

荧光相关光谱单分子检测系统的研究

基于激光共焦构型,构建了一套高灵敏度和高稳定性的荧光相关光谱单分子检测系统。采用高数值孔径物镜使激光束高度聚焦,并用同一物镜收集样品的荧光,单光子计数器用于实时记录荧光信号。优化系统保持物镜焦点、针孔以及单光子计数器光敏区高度同轴。采用60×1.2(NA)的水浸物镜及直径为160μm的针孔得到的检测系统结构参数为ω0和z0分别为0.42μm和1.33μm,照射微区的体积为1.3fL。单个RhodamineGreen分子可获得13倍的信噪比。用该系统获得了小分子和生物大分子(DNA片段和蛋白质)的高质量荧光相关图谱,成功实现了单个分子的检测。     

基于原子力显微镜的高分子单分子力学研究

原子力显微镜(AFM)从根本上改变了人们对单个原子和分子的作用和认识方式。单分子力谱是基于原子力显微镜力的测量方法。概速了近年来利用基于原子力显微镜的单分子力谱研究单个高分子分子内及分子闻作用力的进展。     

Single‐Molecule Methods to Study Membrane Receptor Oligomerization

Membrane receptors control fundamental cellular processes. Binding of a specific ligand to a receptor initiates communication through the membrane and activation of signaling cascades. This activation process often leads to a spatial rearrangement of receptors in the membrane at the molecular level. Single‐molecule techniques contributed significantly to the understanding of receptor organization and rearrangement in membranes. Here, we review four prominent single‐molecule techniques that have been applied to membrane receptors, namely, stepwise photobleaching, Förster resonance energy transfer, sub‐diffraction localization microscopy and co‐tracking. We discuss the requirements, benefits and limitations of each technique, discuss target labeling, present a selection of applications and results and compare the different methodologies.     

Combination of Micro-fluidic Chip with Fluorescence Correlation Spectroscopy for Single Molecule Detection

A single molecule detection technique was developed by the combination of a single channel poly (dimethylsiloxane)/glass micro-fluidic chip and fluorescence correlation spectroscopy (FCS). This method was successfully used to determine the proportion of two model components in the mixture containing fluorescein and the rhodamine-green succinimidyl ester.     

Spectral Versatility of Single Reef Coral Fluorescent Proteins Detected by Spectrally‐Resolved Single Molecule Spectroscopy

We use spectrally‐resolved room temperature single molecule spectroscopy to yield insights into the occurrence and dynamics of spectral forms of single tetramers of DsRed and its variants DsRed2, Fluorescent Timer, DsRed_N42H and AG4. The red‐emitting chromophore in DsRed and all studied variants readily converts into a high quantum efficiency super‐red emitting form. We propose the existence of two super‐red forms of different quantum efficiencies. The observed emission from the green‐emitting chromophore is consistent with bulk spectroscopy. We further observe distinct new spectral forms from each variant, which we attribute to a photoinduced chemical reaction leading to a truncated form of the red‐emitting chromophore analogous to the chromophore in the visible fluorescent protein zFP538. Our results have implications for the accurate interpretation of biological and biochemical processes illuminated by fluorescent proteins as well as for choosing appropriate experimental configurations.     

Spectral Diffusion of Single Dibenzoterrylene Molecules in 2,3‐Dimethylanthracene

We study single dibenzoterrylene molecules embedded in the dipolar disordered crystal 2,3‐dimethylanthracene at 1.25 K. Broad linewidths (about 1 GHz, ～30 times broader than in the anthracene crystal), high saturation excitation intensities (～1000 times larger than in anthracene), as well as strong spectral diffusions are observed. Additionally, spectral jumping is studied by varying the excitation intensity and the temperature. We propose that the spectral diffusion and dynamic disorder in this system arise from the combination of a static disorder with slight reorientations of the methyl groups of the host molecules.     

A Novel Method for Studying the interaction of Macromolecule with Small Molecule by Means of Affinity Capillary Electrophoresis

IntroductionThedeterminationofbindingconstantsplaysanimportantroleforthestudiesofbiomoleculerecognition.Comparedwithtraditionalmethodstheaffinitycapillaryelectrophoresis(ACE)hasadvantagesofsmallsampleconsumption,andobservingtheinteractioninfreesoluti...     

周边硅笼取代的混杂酞菁卟啉三层铽单分子磁体

通过在铽的酞菁卟啉混杂三层的卟啉周边共价连接体积庞大的笼型倍半硅氧烷(POSS),得到了首个包含POSS的混 杂三层Tb₂(Pc)[T(OPOSS)₄PP]₂(1)[H₂Pc=phthalocyanine;H₂T(OPOSS)₄PP=5,10,15,20-tetra{[[N-[heptakis(isobutyl)propoxy]phenyl]octasiloxane]}porphyrin]。为了对比研究,同时合成了类似的三层化合物Tb₂(Pc)(TPP)₂(2)(H₂TPP=5,10,15,20-tetraphenyporphyrin)。尤其值得注意的是,在没有外加磁场的条件下,Tb₂(Pc)[T(OPOSS)₄PP]₂(1)和Tb₂(Pc)(TPP)₂(2)分别表现出单分子磁体和非单分子磁体的性质,这充分说明了共价连接均匀分布的POSS基团有效地分离了磁性核心,从而改善了酞菁卟啉混杂三层的磁性。