古细菌RNase HII与金属离子结合的热力学研究

RNase H是一种专一性水解RNA:DNA杂合链中RNA链的核糖核酸酶,它广泛存在于从原核生物到人的生物体中.本文通过等温滴定量热技术研究了Mg2＋,Mn2＋和Ca2＋与一种古细菌Methanococcus jannaschii中的II型RNase H结合的热力学.首次用这种方法获得了这一结合过程的热力学参数.并证实了这些金属离子与RNase HII按1∶1结合.为RNase HII酶反应机理和折叠研究提供了重要信息.     

古细菌RNase HⅡ与金属离子结合的热力学研究

RNase H是一种专一性水解RNA:DNA杂合链中RNA链的核糖核酸酶,它广泛存在于从原核生物到人的生物体中.本文通过等温滴定量热技术研究了Mg2+,Mn2+和Ca2+与一种古细菌Methanococcusjannaschii中的Ⅱ型RNase H结合的热力学.首次用这种方法获得了这一结合过程的热力学参数.并证实了这些金属离子与RNaseHⅡ按1:1结合.为RNase HⅡ酶反应机理和折叠研究提供了重要信息.     

聚合位点对齐聚乙烯基噻吩光谱的影响

利用密度泛函理论PBE0方法,在6-31G基组水平上,对12种采用不同聚合位点的乙烯基噻吩二聚体分子进行了全优化,得到分子的紫外-可见吸收光谱.探讨了聚合位点对齐聚乙烯基噻吩吸收光谱、电子亲和势、电离能和重组能的影响,并研究了聚合度对乙烯基噻吩齐聚物吸收光谱的影响.计算结果表明:采用邻位聚合的乙烯基噻吩二聚体的能隙最小,电离能EIP最小,电子亲和势EEA最高,最大吸收波长较大,吸收强度大,λmax=377.33nm,f=1.0242.随着聚合度的增加,齐聚乙烯基噻吩的吸收光谱发生红移,吸收峰变宽,吸光度增大.十六聚体的最大吸收范围为500~1200nm,最大吸收波长为801.28nm时吸收值为7.003×105L·mol~(-1)·cm~(-1).     

苯胺和邻氨基酚共聚的原位紫外-可见光谱电化学研究

采用原位紫外-可见吸收光谱法研究了苯胺(AN)和邻-氨基酚(OAP)在0.5 mol/L H2SO4溶液中的电化学共聚过程.结果表明,在AN和OAP的共聚过程中,OAP首先被氧化生成其阳离子自由基,对应于460 nm处的吸收峰,然后OAP阳离子自由基与继而生成的AN阳离子自由基和溶液中的AN和OAP单体发生交互反应,生成混合二聚物中间体,对应于490 nm处的吸收峰,此混合二聚物中间体再继续反应生成中性低聚物,对应于波长小于460 nm处的吸收峰.在研究不同浓度比的AN和OAP进行电化学共聚时发现,当溶液中OAP浓度增大时,对AN的聚合会产生抑制作用.     

烷基和烷氧基取代聚噻吩的合成、表征与光电性能

Fe(Ⅲ )氧化催化法合成了 4种聚噻吩衍生物 ,3 十二烷基聚噻吩 (Pat12 ) ,3 辛氧基聚噻吩 (Paot8) ,3,4 二 (十二烷基 )聚噻吩 (Pat12 12 )和 3 (十二烷基 )噻吩 3 (辛氧基 )噻吩共聚物 (CoPt12 o8) .发现这些衍生物易溶于多种常用有机溶剂 .用GPC法测定了各聚合物分子量 ,用1 H NMR法表征了各聚合物化学结构 .对比研究了这些聚合物紫外 可见吸收性能 ,光致发光性能和能隙 .对其电致发光性能进行测定的结果 ,得到了Pat12 ,Pat12 12和Paot8的电致发光光谱 .发射峰分别为 6 70nm ,5 6 0nm和 6 4 0nm .发光颜色分别为红色 ,黄色和红橙色 .聚合物的光电性能与主链电子结构有密切关系 .探讨了取代基种类和数量对聚合物能带结构 ,光电性能的影响 .     

2,5-二取代噻吩衍生物的“一锅化”串联合成及光学性质

以芳基乙炔与硫脲为起始原料,通过一锅法,经过在无溶剂条件下的氧化偶联反应和在水相中的成环反应,两步串联绿色合成了2,5-二苯基噻吩及其衍生物.所合成化合物经~1H NMR,~(13)C NMR,HRMS表征,均为目标产物.在此基础上,进一步探索了所合成化合物的UV和荧光性质,实验结果表明,所合成化合物的紫外最大吸收波长在292~341 nm之间,荧光光谱表明该类化合物具有良好的荧光性,在甲醇中最大发射波长在386~454.5 nm之间,在二氯甲烷中测定的最大发射波长在390~412 nm之间.实验结果显示,随共轭体系增大,荧光发射波长发生红移.     

结构对称齐聚(3-甲基噻吩)的电子结构和分子堆积

研究了一类结构对称的新型齐聚(3-甲基噻吩)(二聚体Br2MT和四聚体Br4MT)的电子结构和分子堆积形式.结果表明,随着链的增长,新合成的Br4MT溶液比Br2MT溶液(溶剂CHCl3)的最大紫外吸收波长红移约60 nm,Br2MT和Br4MT的π电子轨道重叠度及斯托克斯位移均较大;广角XRD晶体结构分析表明,该类齐聚(3-甲基噻吩)的π-π堆积晶面间距比聚(3-烷基噻吩)减小了约0.08 nm,分子堆积形式主要为π-共轭平面的堆积,其分子结构趋向于紧密堆积.该结构对称齐聚(3-甲基噻吩)的电子结构和分子堆积形式有利于提高其电荷传输能力.     

噻吩衍生物的合成及其光学性能研究

以3-溴噻吩为原料,通过格氏试剂卤锂交换,在过渡金属催化下双环侨联、烷基取代,合成一种液态状双烷基-二噻吩衍生物材料,正丁基锂与三溴噻吩投料比为2:1时收率最高,达80%以上。通过紫外-可见吸收光谱和荧光光谱对其光线发射、吸收及理论计算做了系统性研究,循环伏安(CV)实验对分子内电荷转移情况进行了测试。结果表明双烷基噻吩衍生物的紫外吸收与3,3-双噻吩相比表现出较宽的光谱吸收范围优势,荧光光学能隙值及量子产率均优于3,3-双噻吩,推测衍生物中噻吩邻位增加的烷基侧链作为有效供电子基团,与主环体的Π电子体系共轭发生了明显的电子离域现象,使得双烷基噻吩衍生物具有较好的紫外-可见吸收和荧光发射响应。双烷基噻吩衍生物在不同非质子溶剂中出现随溶剂极性增大发生的吸收及发射波长红移现象,推测化合物分子与不同极性溶剂产生了相互作用,且在特定光源激发后分子内平面共轭结构产生了不同程度的偶极矩变化。最后利用伏安特性曲线验证了双烷基噻吩衍生物良好的光反应活性和导电优势,为光电材料进一步研究提供了理论基础。     

DNA/RNA与聚阳离子的复合动力学研究

DNA或RNA与聚阳离子形成的复合物被广泛用作非病毒类基因载体。由于静电相互作用的高强度和长程性,在溶液中形成的DNA/RNA复合物往往受动力学控制,其结构随着时间会进一步变化。本文总结了这些年来DNA/RNA与聚阳离子复合形成的复合物动力学研究进展,并提出影响复合物的因素主要有两个:近程静电吸引力和远程静电排斥力之间的竞争,以及复合物内、复合物之间的歧化。揭示DNA/RNA与聚阳离子的复合机理,对于制备具有特定结构和功能的基因载体具有重要意义。     

基于氟代喹喔啉D-A型共轭聚合物的合成及其光电性能

分别以噻吩、联二噻吩和三联噻吩为给体单元,氟代噻吩基喹喔啉为受体单元,通过Stille反应合成了三种新型的聚合物太阳电池材料（PT-TFQ, PTT-TFQ和PTTT-TFQ）,其结构经¹H NMR表征。研究了不同给电子能力的结构单元对其UV-Vis谱光谱、电化学性质以及光伏性能的影响。结果表明,PT-TFQ, PTT-TFQ和PTTT-TFQ氯仿溶液的最大吸收峰分别位于545 nm, 578 nm和649 nm,而薄膜的最大吸收峰相对于溶液的吸收峰分别红移了81 nm, 97 nm和44 nm; PT-TFQ, PTT-TFQ和PTTT-TFQ的开路电压依次降低,分别为0.86 V, 0.60 V和0.50 V;基于三者的器件效率分别为3.19%, 3.10%和2.63%。     

酵母核糖核酸的UV-Vis光谱探针反应的机理研究

采用UV－Vis分光光度法，研究在pH7－8的缓冲溶液中，酵母核糖核酸（RNA）与3－氨基－6－二甲氨基－2－甲基吩嗪盐酸盐（ZR）相互作用；反应生成红色配合物，该配合物的最大吸收波长为540nm；反应前后的吸收光谱变化明显，配合物的吸收峰与试剂本身比较红移90nm；研究了体系的酸度、温度、时间等基本反应条件以及不同类型的离子对体系的影响，发现离子强度的改变对体系的吸光度有明显的影响。     

Spectroscopic studies into the influence of UV radiation on elastin in the presence of collagen

An investigation into the influence of UV irradiation on elastin hydrolysates in the presence of collagen was carried out using UV-Vis spectroscopy and spectrofluorometry. It was found that the absorbance of elastin hydrolysates in solution increased during irradiation more than the absorbance of the elastin/collagen blend. The fluorescence of elastin hydrolysates was observed at 305nm and at 380nm after excitation at 270nm. For the elastin/collagen mixture in solution, fluorescence spectrum shows only one maximum at 305nm. UV irradiation caused fluorescence fading at 305nm. For irradiated elastin the fluorescence at 305nm decreased faster than for the irradiated elastin/collagen mixture. The maximum of the fluorescence peak was shifted for elastin by 4nm, whereas for the elastin/collagen blends the shift was only 1-2nm. All the obtained results point out the ability of mixing elastin and collagen, and suggest that the elastin/collagen mixture in solution is less sensitive to UV irradiation than elastin hydrolysates alone.     

Synthesis of a New Cobalt (II) Complex and its Interaction with DNA

The interaction of metal complexes with DNA has been widely studied by differentmethods such as spectrophotometry, light scattering technique, fluorometry1-3. Manycomplexes such as Co(phen)2 ,Co(en)2 ,Fe(EDTA)2- etc.4,5 have been synthesized and 3+ 3+their effect on DNA has been studied in order to further explain the mechanism of genemutation, anti-cancer or cancer-induced reason and DNA targeted drugs. In this paper,a new cobalt complex was synth…     

Photoregulation of RNA digestion by RNase H with azobenzene-tethered DNA

RNA digestion by RNase H, which is responsible for the antisense effect, was efficiently photoregulated by use of the duplex of azobenzene-tethered sense DNA and native antisense DNA. In the dark, RNA digestion was suppressed because antisense DNA was strongly hybridized with azobenzene-tethered sense DNA, and accordingly RNA was isolated. On UV irradiation, antisense DNA was released from the azobenzene-tethered DNA due to the trans-to-cis isomerization and hybridized with RNA, which was digested by RNase H.     

镉镍电池正极物质中钴的测定

在酸性介质中,Co~(2 )与H_2O形成络合离子[Co(H_2O)_6]~(2 ),呈粉红色,在515nm处有最大吸收。采用光度法测定镉镍电池正极物质中添加剂钴,钴含量在0～20mg/100mL范围内符合比尔定律。此法干扰元素少,易操作。     

Spectrophotometric Determination of Nitrogen Dioxide <Nitrite>

Abstract

A highly sensitive spectrophotometric method has been developed for the determination of nitrogen dioxide (nitrite as NO_z ^?) by reacting manganese dioxide in 1:20 perchloric acid. An amount of manganese dioxide (MnO_z) equivalent to the concentration of nitrogen dioxide becomes soluble due to the reduction of Mn (IV) to Mn (II) by nitrite in acidic medium. The soluble Mn (II) ion is filtered to remove excess of MnO₂ and is oxidized to permanganate ion by periodic acid in presence of phosphoric acid. The violet colored solution shows maximum absorbance at 525 nm. The sensitivity of the method is 0.08 ppm based on 0.0044 absorbance, and Beer's law is obeyed in the concentration range of 0.2 to 10.0 μg/mL of NO₂ ^?. Molar absorbance is found to be 2442 at 525 nm.

In the present investigation NO₂ ^? was treated with excess of MnO₂ in 1:20 perchloric acid where NO₂ ^? reduces equivalent amount of Mn (IV) to Mn (II) and becomes soluble. The soluble Mn (II) was heated to boiling and 25 mg (approx.) periodic acid is added and cooled. The volume of each solution is made to 50 mL in volumetric flask. Reagent blank is prepared in similar way except sodium nitrite solution. The absorbance is measured at 525 nm against reagent blank.     

Change Color Effect and Spectral Properties of Gold Nanoparticle-cationic Surfactants System

The change color effect of gold nanoparticle solutions was studied by means of resonance scattering and absorption spectrometry and scan electron microscopy. The red Au nanoparticles with a size of 10 nm exhibit a resonance absorption peak and a resonance scattering peak all at 525 nm. After some inorganic electrolyte was added to a red Au nanoparticles solution, the color of the solution became blue and the absorbance at 600-700 nm was significantly increased. The ratio of the concentration of rnonovalent cations, at which the resonance scattering of the system at 525 nm is maximal to that of divalent cations, is in the range of 100 : 1--100 ; 1. 8. It is in good agreement with the Schulze-Hardy rule of the coagulation value of electrolyte. After adding some cationic surfactants to the above solution, the color of the solution is in deep blue, with two resonance absorption peaks at 550 and 680 nm, and a greatly enhanced resonance scattering peak at 525 nm. The experiments demonstrate that the stronger the hydrophobicity of the cationic surfactant is, the stronger the change color effect of the Au nanoparticle solution promoted by cationic surfactant is. The change color effect of Au nanoparticle solution is resulted from the increased diameter of Au nanoparticles, and the changes of resonance absorotion DeaR and resonance scattering.     

新型香豆素硼氟荧光染料的合成及其光学性能

以邻氨基苯甲酸甲酯和4-二乙胺基水杨醛为原料,合成了一个新的香豆素喹啉衍生物3-{2-［8-(1H-苯并咪唑-2-基)喹啉-2-基］乙烯基}-7-二乙胺基香豆素(QMC),再与BF₃·Et₂O配位合成了硼氟配合物(BQMC),其结构经¹H NMR和MS(ESI)表征。并对BQMC的光学性能进行了研究。结果表明：BQMC的最大吸收波长在二氧六环中为490 nm,在DMSO中为532 nm; BQMC的最大发射波长在正己烷中为618 nm,在DMSO中为679 nm,与配体QMC相比,最大吸收波长红移了近50 nm,最大发射波长红移了近100 nm, BQMC的Stokes位移值从115 nm增至183 nm。在固态下,BQMC在750~825 nm之间有较宽的荧光发射峰,具有较强荧光。     

A highly selective and colorimetric naked-eye chemosensor for Cu2+

A sample and practical colorimetric naked-eye chemosensor 3-nitro-4-ethylenediamido-nitrobenzene (2) for metal cations was designed and synthesized. It displays high selectivity and sensitivity for Cu2+ by the UV absorption which appeared a new peak at 525 nm and color change from yellow to red by naked-eye in CH3OH/H2O pH 7.6.     

Brilliant cresyl blue as a new red region fluorescent probe for determination of nucleic acids

A fluorescence quenching method was developed for determination of microamounts of nucleic acids by using brilliant cresyl blue (BCB) as a new red region fluorescent probe. In aqueous hexylmethylene tetramine solution, BCB showed maximum excitation and emission wavelengths at 626 and 670 nm, respectively, and the fluorescence of BCB could be greatly quenched by DNA (or RNA). Under optimal conditions, the calibration graphs are linear over the range of 0.02–0.80 μg/ml for SM DNA and 0.25–1.5 μg/ml for yeast RNA. The corresponding detection limits are 7 ng/ml for SM DNA and 25 ng/ml for yeast RNA, respectively. SM DNA can be determinated in the presence of 40% (w/w) RNA, and the relative standard deviation of six measurements is 2.5% for 500 ng/ml SM DNA. The result of the determination of golden staphylococcus DNA by this method was satisfactory.