用经典力学计算氢分子的键长键能及力常数

氢原子中1 s电子的电子云呈球形，电子的最大几率密度分布出现在玻尔半径a0的球壳内，认为几率密度分布及电子云属统计规律，意味着已经使用了宏观时标，这样就使氢分子体系中能量和时间的作用量远大于普郎克常数；根据电子云的交叠，用经典力学计算了基态氢分子的结构常数，获得键长、键能及力常数的表达式分别为采用原子单位（a.u.）时z、e及a0均为1，获得Re=1.414a.u.，De=0.177a.u.，k=0.354a.u.，这些数值与实验值的相对误差分别<1%，<2%和<4%；成键模型直观，物理意义明确，计算中不含任何人为性参数。     

高聚物分子结构对发泡成型的影响

介绍了高聚物的分子结构和塑料的发泡成型，从微观的角度分析了高聚物的分子结构及动态加工因素对发泡成型的影响。     

鱼类抗菌肽的研究进展

抗菌肽是鱼类先天免疫的重要组成部分,有望成为下一代抗菌药物。收集了鱼类抗菌肽的5个大类Piscidin, Defensin, Hepcidin, Cathelicidin, Pardaxin及25个亚类的基本信息。分析了其电荷、疏水结构和二级结构的特征和比较了其对细菌、真菌的抗菌谱。探讨了电荷、疏水性、二级结构和二硫键等影响抗菌肽作用的机制。指出开发表面固定化技术,研究抗菌肽的缓控释新剂型,机器学习有助于开发活性高、抗菌谱广和低毒的新型抗菌肽。抗菌肽应用于渔业生产和防病治病,有助于开发绿色环保养殖技术,促进养殖渔业健康可持续发展。     

Strategy for Internal Labeling of Large RNAs with Minimal Perturbation by Using Fluorescent PNA

Fluorescence techniques for the investigation of biomolecules and their folding pathways require an efficient labeling strategy. A common method to internally label large RNAs involves the introduction of long loops for hybridization of fluorophore‐carrying DNA strands. Such loops often disturb the structure, and thus the functionality, of the RNA. Here we show, in a proof of concept study with a >600 nucleotide group II intron ribozyme, that the usage of the nucleic acid analogue peptide nucleic acid (PNA) is more efficient in several aspects, minimizing the required structural modifications of the RNA. We demonstrate by various methods, including smFRET, that much smaller concentrations and shorter PNAs can be applied, compared to DNA, for rapid and specific internal RNA labeling. The folding pathway and catalytic activity of this large ribozyme is only minimally affected by the PNA, but the background signal is significantly reduced.     

Direct Measurement of Raman Scattering Tensor of Orientation‐Fixed Single Iodine Molecules

Raman spectroscopy is the most widely used noninvasive analytical technique. Apart from the fingerprint Raman frequency for identifying vibrational mode of certain functional groups, the Raman scattering tensor can also be used to determine the corresponding vibrational symmetry as well as the orientation of this functional group with respect to the rest of the molecule. For gaseous single molecules, only limited structural information can be obtained from Raman spectroscopy owing to their freely rotating and randomly oriented nature. Here, a method, for the first time, is developed to directly determine the Raman scattering tensor on orientation‐fixed single iodine molecules, which are confined inside the nano‐sized channels of zeolite AlPO₄–11 (AEL) single crystal. The experimental results are in good agreement with theoretical predictions based on a density functional theory. The optical transparency and appreciable size of the crystal facilitate the Raman exploration and the 3D manipulation. It is also demonstrated that iodine molecules' orientations are randomly distributed inside the nano‐channels of AlPO₄–5 (AFI) crystal, which indicates that by carefully choosing the relevant zeolite crystal, the big family of zeolites can be utilized as directing template database for orienting a large number of guest molecules to estimate their structures by polarized Raman spectroscopy.     

分子自组装对缔合压裂液黏度“回复”的机理分析

近些年,通过疏水缔合聚合物与表面活性剂复配所形成的具有"超分子结构"的缔合体系,被作为新型清洁压裂液已有相关的报道。绝大多数文章关注稠化剂的研发和性能评价,对这种缔合压裂液体系的成网机理、剪切"回复性"机理等基础研究较少。通过变剪切流变实验、环境扫描电镜、支撑剂悬浮实验,对缔合压裂液体系的成网机理、剪切"回复性"机理进行了分析研究,从可视化的角度直观地分析并阐述了分子自组装对缔合压裂液体系表观黏度"回复"的作用。分析研究结果表明,缔合压裂液的"空间网络状结构"是通过疏水支链与表面活性剂"共用"胶束、疏水缔合聚合物分子间缔合和分子间缠绕的方式形成的;剪切作用撤销以后,拆散了的表面活性剂自组装成新的"胶束"并与剪碎了的疏水缔合聚合物的疏水支链,重新自组装形成新"网络状结构";分子层间的"滑移"作用,使缔合压裂液体系新"网络状结构"处于一种"动态平衡"状态,并以新构建的"网络状结构"悬浮支撑剂。      

Nanogap Electrodes towards Solid State Single‐Molecule Transistors

With the establishment of complementary metal‐oxide‐semiconductor (CMOS)‐based integrated circuit technology, it has become more difficult to follow Moore's law to further downscale the size of electronic components. Devices based on various nanostructures were constructed to continue the trend in the minimization of electronics, and molecular devices are among the most promising candidates. Compared with other candidates, molecular devices show unique superiorities, and intensive studies on molecular devices have been carried out both experimentally and theoretically at the present time. Compared to two‐terminal molecular devices, three‐terminal devices, namely single‐molecule transistors, show unique advantages both in fundamental research and application and are considered to be an essential part of integrated circuits based on molecular devices. However, it is very difficult to construct them using the traditional microfabrication techniques directly, thus new fabrication strategies are developed. This review aims to provide an exclusive way of manufacturing solid state gated nanogap electrodes, the foundation of constructing transistors of single or a few molecules. Such single‐molecule transistors have the potential to be used to build integrated circuits.     

A Bipedal DNA Motor that Travels Back and Forth between Two DNA Origami Tiles

In this work, the successful operation of a dynamic DNA device constructed from two DNA origami building blocks is reported. The device includes a bipedal walker that strides back and forth between the two origami tiles. Two different DNA origami tiles are first prepared separately; they are then joined together in a controlled manner by a set of DNA strands to form a stable track in high yield as confirmed by single‐molecule fluorescence (SMF). Second, a bipedal DNA motor, initially attached to one of the two origami units and operated by sequential interaction with “fuel” and “antifuel” DNA strands, moves from one origami tile to another and then back again. The operational yield, measured by SMF, was similar to that of a motor operating on a similar track embedded in a single origami tile, confirming that the transfer across the junction from one tile to the other does not result in dissociation that is any more than that of steps on a single tile. These results demonstrate that moving parts can reliably travel from one origami unit to another, and it demonstrates the feasibility of dynamic DNA molecular machines that are made of more than a single origami building block. This study is a step toward the development of motors that can stride over micrometer distances.     

用于DNA分子检测的纳米电极

基于纳米孔技术的新兴单分子传感技术已开发用于DNA测序,使得测序技术读取数据更快、测序成本降低、测序样品简化、无需标记.纳米孔孔内集成横向纳米电极可实现二维双通道同时检测易位信号的变化,从而提高纳米孔测序的精确度.目前纳米电极的制备方法主要包括:机械可控劈裂结法、电子束光刻法、电子束诱导沉积法、聚焦离子束刻蚀法、透射电镜刻蚀法等.分析纳米电极不同制备方法、应用范围、表征及其优缺点,可为后续纳米孔技术应用到DNA测序平台提供高效、稳定的选择.