水溶液中DNA紫外辐射损伤的分子机制研究

以激光喇曼光谱分析技术,对不同紫外辐射时间条件下ＤＮＡ在水溶液中产生的损伤状况进行研究,结果表明,体外条件下单纯ＤＮＡ水溶液中由紫外辐射直接造成Ｃ→Ｔ的可能性（具体反映在Ｃ→Ｕ这一过程中）是不存在的。胞嘧啶有Ｃ４原子处氨基减少可能,但并无假设衍生形成的尿嘧啶的Ｃ４Ｏ增色表现,不支持胞嘧啶脱氨基直接转变为酮式（成为尿嘧啶）的模型。胞嘧喧Ｎ４Ｈ变形振动的减色似可能证明胞嘧啶的亚氨基化,６１６ｃｍ＾－１     

密度泛函方法研究气相胞嘧啶的互变异构化

分别采用7种基组、3种理论方法对胞嘧啶异构体Cyt1的结构进行优化,通过与Cyt1的实验结果进行比较,选取了适合研究胞嘧啶分子的B3LYP/6311+G方法.用该方法对胞嘧啶分子的8种异构体构型进行了充分优化,研究了其中能量较低的6种胞嘧啶异构体的互变异构化过程.对于得到的所有优化构型都进行了频率分析.对于基态构型,所有的频率都是正的;对于过渡态构型,只有一个虚频.同时,做了详尽的内禀反应坐标计算,以保证所得到的过渡态连接相应的始末异构体.所有给出的能量都已做了零点能校正.理论研究结果可以对已有的实验结果给予合理解释.     

基序B参与调控模板依赖的聚合酶抑制作用

RNA依赖的RNA聚合酶是参与新冠病毒进行RNA复制与转录的主要分子机器. 之前的实验研究表明瑞德西韦在模板链上时存在两次抑制作用,即不仅可以抑制与之互补的尿嘧啶核苷三磷酸的加成,还可以抑制下一位核苷三磷酸的加成. 然而,第二次抑制作用的分子机制尚未阐明. 本文运用了分子动力学模拟,发现瑞德西韦在模板链上的第二次抑制不是直接作用于核苷酸在活性位点的加成,而是源于瑞德西韦从+1位点到-1位点的迁移过程受到阻碍,这将导致活性位点无法空出,核苷三磷酸无法进入活性位点从而产物链的延长被终止. 首先,发现了基序B中G683会和瑞德西韦的1''-氰基相互作用,导致移位后态的RNA双链配对稳定性低于移位前态,从而使得瑞德西韦的移位在热力学上不易发生. 其次,由于瑞德西韦的1''-氰基在迁移过程中会与基序B的S682产生位阻,进一步从动力学上阻碍了瑞德西韦动态移位的发生. 本研究不仅揭示了基序B上两个相邻且高度保守的氨基酸可以调控瑞德西韦沿模板链的移位过程,同时,本文的发现也进一步完善了对瑞德西韦抑制新冠病毒RNA复制和转录的分子机制的理解.     

HIV蛋白酶多肽抑制剂的理论研究

艾滋病病毒的发现距今已有二十多年的历史了.它仍然以很快的速度在全球范围速蔓延.研发抗艾滋病药物是当代药学的重大课题之一.在以往研究的基础上,我们利用分子叠合和分子对接这两种分子模拟手段,把从PDB数据库中得到的与HIV蛋白酶结合的12个肽类分子和已经上市的抗艾滋病的药物Saquinavir做比较.根据结构相同或相近的分子具有相同的活性原理,运用分子叠合初部判断分子活性,特别是药效团的特征比对揭示了分子活性的原因,为进一步的药物设计奠定了良好的基础.进而采用分子对接的分子模拟方法对这12个肽类分子的活性构象进行了深入的分析,预测出了这12个分子对HIV病毒蛋白酶的不同抑制作用.研究发现:P01、P05、P09、P12可能与已知药物Saquinavir在与HIV蛋白酶结合时具有相似的活性,其中P9的活性最强,有望成为抗HIV药物的理想前体,为下一步的HIV药物的设计研究提供了理论依据.     

紫玉兰素A与人端粒G-四链体相互作用的光谱学研究,第一个木脂素类衍生物与G-四链体相互作用

人端粒G-四链体结构是指端粒末端富含鸟嘌呤(G)的DNA序列在一价阳离子(如K+和Na+)诱导下通过G碱基间Hoogsteen氢键连接形成的DNA二级结构.能够稳定端粒G-四链体的配体通常为端粒酶抑制剂,其可能成为抗肿瘤药物.应用CD,FRET,NMR光谱方法第一次较全面地研究了一种木脂素衍生物,紫玉兰素A (liliflorin A)与人端粒序列dGGG (TTAG(G)3G-四链体HTG21的相互作用,采用分子对接技术进一步研究紫玉兰素A与人端粒序列dTAGGG(TIAGC)3 G-四链体HTG23的结合位点.CD实验数据表明紫玉兰素A提高HTG21解链温度,FRET实验测得4.0μmol·L-1紫玉兰素A可以将HTG21稳定温度提高3.2℃.NMR实验结果表明,加入紫玉兰素A三小时后HTG21核磁谱图出现明显变化.分子对接结果表明紫玉兰素A结合到HTG23较宽沟槽上,结合位点为G9,G10,G16和G17.紫玉兰素A是第一个能够选择性稳定人端粒G四链体HTG21的木脂素类衍生物配体.实验结果为以人端粒G-四链体为靶点的抗肿瘤药物设计提供了新型候选化合物.     

用全内反射瞬逝场照明磁镊研究Bloom解旋G-四联体

G-四联体(G-quadruplex,G4)是广泛存在于细胞基因组中的一种DNA结构,在DNA的代谢如复制、转录、同源重组等过程中起重要作用.G4解旋酶近年来受到广泛研究,其中Bloom(BLM)解旋酶的研究已经相当丰富,但仍有一些基本问题不清楚.我们应用全内反射瞬逝场照明磁镊对BLM解旋G4的动力学过程进行了深入研究,观察到了BLM解旋G4的分步过程.相对于单分子荧光共振能量转移技术而言,借助磁镊的长时间观测性能,我们在近饱和三磷酸腺苷(ATP)浓度的实验体系中观察到BLM长时间反复解开G4或者长时间维持G4于打开状态的两种作用方式.最后,使用相同的实验条件做了单分子荧光共振能量转移实验,确定了加载2-3 pN的外力对BLM解旋G4没有显著影响.     

胞嘧啶分子拉曼光谱研究

本文通过实验测量了胞嘧啶的常规拉曼光谱,有四个弱拉曼峰在以前胞嘧啶的常规拉曼光谱中未检测到。采用密度泛函(Density Function Theory)B3LYP/6-31+G(d,p)计算了胞嘧啶分子的拉曼光谱。结合理论计算结果对实验拉曼光谱振动模式进行了指认,并对其中几个拉曼峰非常弱的原因进行了分析。     

氟代吡啶阳离子的理论研究

利用量子化学密度泛函理论B3LYP方法及 6 31G(d ,p)、6 311G(d ,p)、6 31+G(d ,p)和 6 311+G(d ,p)基组对五氟代吡啶、2 ,6 二氟代吡啶和 2 氟代吡啶分子的阳离子进行了计算研究 .B3LYP构型优化和频率分析计算结果表明这三种氟代吡啶阳离子的结构分别具有C2v、C2v和Cs 对称性 ,电子基态分别为2 A2 、2 A2 和2 A″ .对离子和分子的计算构型做了比较 .利用B3LYP方法和不同的基组对这三种阳离子及其分子进行了自然布居分析计算 .用B3LYP方法对这三种阳离子 (自由基 )中的超精细结构进行了计算 ,对五氟代吡啶、2 ,6 二氟代吡啶和2 氟代吡啶分子的垂直电离势和绝热电离势进行了计算 ,与实验值符合得很好     

苯氨基磺酸衍生物作为HPTPβ抑制剂的Topomer CoMFA研究及分子对接

采用Topomer CoMFA方法对27个苯氨基磺酸衍生物进行了三维定量构效关系研究。得到了3D-QSAR模型,其交互验证系数q2为0.713,非交叉相关系数r2为0.995,主成分数N为6,标准估计误差SEE为0.183。结果表明该模型有较好的预测能力。采用Topomer Search技术在ZINC数据库中进行R基的筛选,并设计了5个新分子,最后用分子对接技术研究了新分子与苯氨基磺酸衍生物大分子蛋白的作用模式,从结果中可以看到,新分子与苯氨基磺酸衍生物蛋白的A/ARG220、A/ARG63和A/ASN115位点作用显著.     

3种核酸碱基(胞嘧啶、胸腺嘧啶、尿嘧啶)在银电极表面的吸附形态

通过表面增强拉曼散射研究了胞嘧啶、胸腺嘧啶和尿嘧啶在粗糙银电极表面上的吸附形态随电极电位的变化关系.大量的结构信息可从丰富的表面拉曼信号及其随电极电位相应的变化而获得.分析表明在电极电位负移过程中,胞嘧啶一直通过N3位垂直吸附于纳米银颗粒表面;而胸腺嘧啶分子和尿嘧啶分子在表面的吸附状态都随电位改变发生了变化,较正电位下...     

Electron microscopy studies on luteovirid transmission by aphids

Transmission electron microscopy (TEM) observations have been extensively applied to follow the route of luteovirids in their vectors. Luteovirids are icosahedral plant viruses which are phloem-limited and strictly transmitted in a circulative manner by aphids. Virus particles, acquired by aphids while feeding on an infected plant, circulate in the aphid's body without replication and are internalized during this process in two different cell types (intestinal and accessory salivary gland cells). The endocytosis mechanism at the gut level seems to rely on a clathrin-mediated entry process and virions are observed in the aphid's gut cells in various vesicular structures. After exocytosis from intestinal cells, virions are released in the aphid's body cavity where they are thought to bind to symbionin, an endosymbiotic protein. Transcytosis of the accessory salivary gland cells occurs similarly as at the gut level but in the reverse direction. Using engineered virus mutants, viral proteins required for transmission and involved in virus retention in the hemocoel have been identified. Virus mutants poorly or non aphid-transmitted have also been localized in the aphid's body by TEM. These observations reveal the crucial role of the minor capsid protein in gut internalization. While not strictly required, this protein seems to play an important role in the efficiency of this process by interacting with putative virus receptors localized on the gut apical membrane. More recently, some aphid proteins have also been shown to exhibit in vitro virus binding capacity and could potentially be components of the endocytotic apparatus.     

Design, synthesis and biological evaluation of indolizine derivatives as HIV-1 VIF–ElonginC interaction inhibitors

The HIV-1 viral infectivity factor (VIF) protein is essential for viral replication. VIF recruits cellular ElonginB/C-Cullin5 E3 ubiquitin ligase to target the host antiviral protein APOBEC3G (A3G) for proteasomal degradation. Thus, the A3G-Vif–E3 complex represents an attractive target for the development of novel anti-HIV drugs. In this study, we describe the design and synthesis of indolizine derivatives as VIF inhibitors targeting the VIF–ElonginC interaction. Many of the synthesized compounds exhibited obvious inhibition activities of VIF-mediated A3G degradation, and 5 compounds showed improvement of activity compared to the known VIF inhibitor VEC-5 (1) with IC $_{50 }$ values about 20 $\upmu $ M. The findings described here will be useful for the development of more potent VIF inhibitors.     

Application of transmission electron microscopy to the clinical study of viral and bacterial infections: present and future

Transmission electron microscopy has had a profound impact on our knowledge and understanding of viruses and bacteria. The 1000-fold improvement in resolution provided by electron microscopy (EM) has allowed visualization of viruses, the existence of which had previously only been suspected as the causative agents of transmissible infectious disease. Viruses are grouped into families based on their morphology. Viruses from different families look different and these morphological variances are the basis for identification of viruses by EM. Electron microscopy initially came to prominence in diagnostic microbiology in the late 1960s when it was used in the rapid diagnosis of smallpox, by differentiating, on a morphological basis, poxviruses from the less problematic herpesviruses in skin lesions. Subsequently, the technique was employed in the diagnosis of other viral infections, such as hepatitis B and parvovirus B19. Electron microscopy has led to the discovery of many new viruses, most notably the various viruses associated with gastroenteritis, for which it remained the principal diagnostic method until fairly recent times. Development of molecular techniques, which offer greater sensitivity and often the capacity to easily process large numbers of samples, has replaced EM in many areas of diagnostic virology. Hence the role of EM in clinical virology is evolving with less emphasis on diagnosis and more on research, although this is likely only to be undertaken in specialist centres. However, EM still offers tremendous advantages to the microbiologist, both in the speed of diagnosis and the potential for detecting, by a single test, any viral pathogen or even multiple pathogens present within a sample. There is continuing use of EM for the investigation of new and emerging agents, such as SARS and human monkeypox virus. Furthermore, EM forms a vital part of the national emergency response programme of many countries and will provide a frontline diagnostic service in the event of a bioterrorism incident, particularly in the scenario of a deliberate release of smallpox virus. In the field of bacteriology, EM is of little use diagnostically, although some bacterial pathogens can be identified in biopsy material processed for EM examination. Electron microscopy has been used, however, to elucidate the structure and function of many bacterial features, such as flagellae, fimbriae and spores and in the study of bacteriophages. The combined use of EM and gold-labelled antibodies provides a powerful tool for the ultrastructural localisation of bacterial and viral antigens.     

Hydrodynamic cavitation efficiently inactivates potato virus Y in water

Waterborne plant viruses can destroy entire crops, leading not only to high financial losses but also to food shortages. Potato virus Y (PVY) is the most important potato viral pathogen that can also affect other valuable crops. Recently, it has been confirmed that this virus is capable of infecting host plants via water, emphasizing the relevance of using proper strategies to treat recycled water in order to prevent the spread of the infectious agents. Emerging environmentally friendly methods such as hydrodynamic cavitation (HC) provide a great alternative for treating recycled water used for irrigation. In the experiments conducted in this study, laboratory HC based on Venturi constriction with a sample volume of 1 L was used to treat water samples spiked with purified PVY virions. The ability of the virus to infect plants was abolished after 500 HC passes, corresponding to 50 min of treatment under pressure difference of 7 bar. In some cases, shorter treatments of 125 or 250 passes were also sufficient for virus inactivation. The HC treatment disrupted the integrity of viral particles, which also led to a minor damage of viral RNA. Reactive species, including singlet oxygen, hydroxyl radicals, and hydrogen peroxide, were not primarily responsible for PVY inactivation during HC treatment, suggesting that mechanical effects are likely the driving force of virus inactivation. This pioneering study, the first to investigate eukaryotic virus inactivation by HC, will inspire additional research in this field enabling further improvement of HC as a water decontamination technology.     

20,20-二氯-1,10-二甲氧基三环[5,4,0,012,19]十一碳 -1,5,6-三烯结构和性质的理论研究

在RHF/6-31G、B3LYP/6-31G和MP2/6-31G水平下优化了标题化合物的平均几何构型,用B3LYP/6-31G方法计算了该化合物的红外光谱.并用GIAO分别在B3LYP/6-31G、B3LYP/6-311G和B3LYP/6-311++G水平对该化合物的核磁共振谱进行了研究.计算结果与实验结果吻合很好.同时对在合成过程中发现的两个中间产物进行了理论计算,研究证实了合成标题化合物时中间产物的存在.     

Ventral and dorsal streams processing visual motion perception (FDG-PET study)

Background

Cullin ubiquitin ligases are activated via the covalent modification of Cullins by the small ubiquitin-like protein nedd8 in a process called neddylation. Genetic mutations of cullin-4b (cul4b) cause a prevalent type of X-linked intellectual disability (XLID) in males, but the physiological function of Cul4B in neuronal cells remains unclear.

Results

There are three major isoforms of Cul4B (1, 2, and 3) in human and rodent tissues. By examining the endogenous Cul4B isoforms in the brain, this study demonstrates that Cul4B-1 and Cul4B-2 isoforms are unneddylated and more abundant in the brain whereas the lesser species Cul4B-3 that misses the N-terminus present in the other two isoforms is neddylated. The data suggest that the N-terminus of Cul4B inhibits neddylation in the larger isoforms. Immunostaining of human NT-2 cells also shows that most Cul4B is unneddylated, especially when it is localized in the process in G0-synchronized cells. This study demonstrates that Cul4B accumulates during mitosis and downregulation of Cul4B arrests NPCs and NT-2 cells in the G2/M phase of the cell cycle. In both human and rodent brain tissues, Cul4B-positive cells accumulate ??-catenin in the dentate subgranular zone and the subventricular zone. These Cul4B-positive cells also co-express the MPM-2 mitotic epitope, suggesting that Cul4B is also necessary for mitosis progression in vivo.

Conclusions

This study provides first evidence that unneddylated Cul4B isoforms exist in the brain and are necessary for mitosis progression in NPCs. The data suggest that unneddylated Cul4B isoforms specifically inhibits ??-catenin degradation during mitosis. Furthermore, unneddylated Cul4B may play a role in addition to cell cycle since it is exclusively localized to the processes in starved NT-2 cells. Further analyses of the different isoforms of Cul4B will help understand the cognitive deficits in Cul4B-linked XLID and give insights into drug and biomarker discoveries.     

硫酸氢酯类药剂浮选铜的量子化学研究

我国矿产资源日益匮乏,对浮选药剂的选择性和安全性提出了更高的要求,设计新型药剂势在必行.运用密度泛函理论,选取B3LYP/6-311+G(d, p)方法基组,对碳原子数在15～21的硫酸氢酯类浮选药剂浮选铜离子进行了计算研究.通过几何参数优化、电荷密度分布及吸附能变化,探讨了碳原子数为15～21的硫酸氢酯类浮选药剂对铜离子浮选性能的改良,综合考虑各种因素, C_(17)(十七烷基硫酸氢酯)浮选效果较好.结论对研究浮选机理及分子模拟设计新型浮选药剂具有指导意义.     

Replication of microchannel structures in polymers using laser fabricated glass–ceramic stamp

A new microreplication process with photo-etchable glass–ceramic stamps and polymers is presented. This process has two main advantages: a rapid master fabrication with a laser process and a flexible replication process compared with conventional nano- or microreplication technique on polymers. Photo-etchable glass–ceramics are used for the master stamp. Micropatterns can be rapidly transferred with a laser direct writing process and the removal of the glass–ceramics can be efficiently achieved with a wet etching process. Therefore, microstructures with flat bottom surfaces and straight sidewall structures can be obtained, which is difficult in the laser direct writing process. A microstamping process of applying heat and pressure, also referred to as hot embossing lithography or microstamping, can replicate microstructures on polymer surfaces. In this work, the fabricated glass–ceramic stamps are used for the replication process and various replicated polymer microstructures are presented.     

Facile preparation of magnetically functionalized graphite nanosheets for porcine pancreatic lipase immobilization

We report that silicon nanoparticles (SiNPs) with typical sizes from 5 to 50 nm prepared by grinding of porous silicon can act as efficient scavengers of human immunodeficiency virus (HIV) and respiratory syncytial virus (RSV). In vitro studies have revealed a strong suppression of the viral activity in the presence of SiNPs with concentration above 0.1 and 0.01 mg/mL for HIV and RSV, respectively. The observed effect is explained by binding of the virions with SiNPs that is supposed to be universal for different enveloped viruses. Because of the cytotoxic concentration of SiNPs is of the order of 1 mg/mL, SiNPs can be proposed for applications in new harmless methods of antiviral treatment.