蜂毒肽与CT-DNA的相互作用

通过圆二色光谱、紫外光谱、荧光光谱以及等温滴定量热等技术研究了蜂毒肽(Mel)与小牛胸腺DNA(CT-DNA)之间的相互作用以及构象变化。结果表明Mel可以与CT-DNA形成复合物。复合物的形成使得Mel的构象发生变化,由无规卷曲转变为α-helix,Mel中色氨酸残基处于更加疏水的环境。同时,CT-DNA的结构发生变化,解链温度(T_m)从64.3℃增加到66.2℃。Mel与CT-DNA的结合常数(K_a)约为10⁵L·mol^-1,复合物的形成是吸热的过程,主要依靠静电作用,其次是疏水作用。     

光谱法研究百草枯与小牛胸腺DNA的相互作用

以亚甲基蓝(MB)为分子探针,用紫外-可见光谱、荧光光谱、荧光偏振和圆二色光谱研究了百草枯与小牛胸腺(ctDNA)的相互作用.MB分子主要以嵌插方式结合到ctDNA双螺旋结构上,而百草枯则以非竞争方式抑制MB与ctDNA的结合;百草枯对MB-ctDNA体系的荧光偏振以及百草枯对ctDNA圆二色光谱的影响,结果均表明百草枯与ctDNA主要作用方式为非嵌插结合.NaCl对百草枯与ctDNA的结合具有显著的抑制作用,因此可以推断带正电荷的百草枯离子可能通过与ctDNA链上带负电荷的磷酸基以静电相吸的方式结合而堆积在ctDNA双螺旋表面,引起ctDNA收缩,减弱了结合位点附近MB与ctDNA的静电作用;这可能由于钠离子中和了ctDNA磷酸基上的负电荷,从而削弱了百草枯与ctDNA间的静电作用.通过Scatchard方程计算,获得了百草枯与ctDNA的结合常数为1.80×104L·mol-1.     

光谱法与共焦荧光成像法研究罗丹明B与ct-DNA的相互作用

采用吸收光谱、荧光光谱以及共焦荧光成像技术研究生理条件下罗丹明B(Rhodamine B,RB)与小牛胸腺DNA(ct-DNA)的相互作用以及相互作用模式。光谱研究结果显示,在450~650 nm的吸收光谱范围内,ct-DNA溶液对罗丹明B有减色作用;在560~660 nm荧光发射光谱范围内,ct-DNA对罗丹明B有荧光猝灭作用。同时,随着ct-DNA的加入,罗丹明B溶液的荧光偏振值发生变化,说明罗丹明B与ct-DNA能发生相互作用。在竞争性实验中,罗丹明B未能将亚甲基蓝(MB)从MB-ct-DNA复合体系中置换出来,说明罗丹明B与ct-DNA通过沟槽结合方式发生相互作用。共焦荧光成像结果显示,ct-DNA加入后,罗丹明B的荧光猝灭十分明显。利用罗丹明B和4',6-二脒基-2-苯基吲哚(DAPI)对He La细胞染色后进行共焦荧光成像,结果进一步证实罗丹明B与ct-DNA是通过沟槽结合作用将细胞核染成红色。     

磁性纳米氧化铁与小牛胸腺DNA相互作用研究

以微波辅助共沉淀法合成磁性纳米氧化铁(MNPs), 分别采用紫外-可见吸收光谱(UV-vis)、拉曼光谱(Raman)及琼脂糖凝胶电泳(GE)研究其与小牛胸腺DNA (ct DNA)的相互作用. UV-vis显示出明显的增色效应, 这是由DNA分子受MNPs的干扰碱基外露而引起的|Raman研究表明DNA分子碱基、脱氧核糖以及磷酸骨架均受到MNPs一定程度的干扰|而GE证实了MNPs并未使DNA分子发生断裂、双链解开等本质性变化. 该研究对MNPs在生物医学领域的安全应用具有重要意义.     

巯嘌呤金属配合物与小牛胸腺DNA的作用

用溴化乙锭为探针研究了巯嘌呤(mercaptopurine, MP)金属配合物与小牛胸腺 DNA的作用机制，探讨了其作用模式，即巯嘌呤与DNA是非嵌插结合，巯嘌呤金属酴 物与DNA之间的作用为静电方式和一定的嵌入方式。并求得巯嘌呤金属配合物与 DNA的结合常数。     

Preliminary Study on Cordycepin-DNA Interaction by Raman Spectroscopy

The interaction of cordycepin with calf thymus DNA was investigated at physiological pH with drug/DNA molar ratio of 8. The Raman spectroscopy results indicated that the intercalation of high concentration cordycepin and the interaction of cordycepin with PO2 group led to a major reduction of B-form DNA structure in favor of A-form DNA.     

2-吡咯类酰腙的合成、晶体结构及与小牛胸腺DNA的相互作用

以2-吡咯甲酰肼与2,4-二羟基苯甲醛和2-羟基-3-甲氧基苯甲醛经缩合反应合成2,4-二羟基苯甲醛-2-吡咯甲酰腙C₁₂H₁₁N₃O₃(Ⅰ)和2-羟基-3-甲氧基苯甲醛-2-吡咯甲酰腙C₁₃H₁₅N₃O₄(Ⅱ),并利用红外光谱、元素分析、¹H NMR、X射线单晶衍射和热重分析进行表征,结果表明晶体Ⅰ属单斜晶系,空间群为P2₁/c,Z=4,晶胞参数为a=1.2586(4) nm,b=0.8050(3) nm,c=1.1914(4) nm;晶体Ⅱ为正交晶系,空间群为P2₁2₁2₁,Z=4,晶胞参数为a=0.4756(2) nm,b=1.2491(6) nm,c=2.2145(11) nm。 热重结果显示,化合物Ⅰ和Ⅱ最大热分解峰分别出现在267.59和284.79 ℃,表观活化能分别为176.6和122.9 kJ/mol,表明化合物Ⅰ和Ⅱ具有较高的热稳定性。 利用粘度实验和微量热实验研究了化合物Ⅰ和Ⅱ与CT-DNA的相互作用,均显示两种化合物均与CT-DNA发生了插入作用,且相互作用过程放热,焓变值分别为ΔH(Ⅰ)=4.67 kJ/mol和ΔH(Ⅱ)=4.40 kJ/mol。     

Electrochemical Study on the Interaction of Irinotecan with Calf Thymus Double Stranded DNA

Voltammetric behavior of Irinotecan (CPT‐11) was studied in a phosphate buffer (0.002 mol·L^?1, pH 7.5) solution at the hanging mercury drop electrode (HMDE) using cyclic voltammetry (CV). CPT‐11 showed two irreversible cathodic peaks at ?1.01 V and ?1.09 V which involved two electrons and two protons in each reduction step. In addition, the interaction of Irinotecan with double‐stranded calf thymus DNA (ds‐DNA) was studied by CV at the HMDE employing an irreversible electrochemical equation. As a result of the reaction with ds‐DNA, the reduction peaks related to CPT‐11 were shifted in a negative direction and the peak currents were decreased. The diffusion coefficients of CPT‐11 in the absence (D_f) and presence (D_b) of ds‐DNA were calculated as 2.8×10^?5 cm²·s^?1 and 1.6×10^?5 cm²·s^?1 respectively. The binding constant (K=1.0×10⁴ L·mol^?1), and binding site size (s=0.60) of CPT‐11 interacting with ds‐DNA were obtained simultaneously by non‐linear fit analysis. The results demonstrate that the main interaction mode of CPT‐11 with ds‐DNA is electrostatic.     

红景天苷与DNA的结合作用研究

在pH=7.4的生理酸度条件下,采用荧光光谱和紫外-可见光谱法,并结合I-效应、离子强度的影响、DNA熔点及粘度测定等实验手段,研究了红景天苷与小牛胸腺DNA的相互作用.结果表明,DNA对红景天苷的内源荧光有明显的猝灭作用,猝灭过程为静态猝灭.由荧光猝灭实验数据,计算出不同温度下红景天苷与DNA之间作用的结合常数和热力...     

农药异丙威与小牛胸腺DNA的作用研究

在生理酸度条件下,采用紫外光谱和荧光光谱法研究异丙威与小牛胸腺DNA的作用表明:DNA对异丙威的荧光有明显的猝灭作用,属于静态猝灭方式;K4[Fe(CN)6]猝灭试验发现DNA对异丙威有明显的保护作用,离子强度的改变对异丙威和异丙威-DNA体系的荧光均无明显影响;异丙威的加入使DNA的熔点升高,并且异丙威能够竞争置换EB与DNA的结合位点。上述实验也表明,异丙威以嵌插方式作用于DNA的结合位点,有可能通过形成DNA加合物的形式造成DNA损伤,从而最终导致基因突变。     

光谱法及分子模拟法研究杨梅素与ct-DNA的相互作用

采用紫外光谱、荧光光谱结合亚甲基蓝荧光探针(MB)、圆二色谱(CD)以及分子模拟等技术研究了生理条件下杨梅素与小牛胸腺DNA(ct-DNA)的相互作用,探索了其可能的结合位点与作用机制。热力学参数显示ΔH0、ΔS0,说明杨梅素与ct-DNA通过氢键和范德华力发生相互作用。光谱研究显示,ct-DNA能够猝灭杨梅素的内源荧光,猝灭方式为静态猝灭,两者的结合常数为1.86×103mol-1,结合位点数为1。在竞争性实验中杨梅素未能将MB从MB-DNA复合体系中游离出来,说明其与ct-DNA的作用方式为沟槽结合。圆二色光谱研究表明,杨梅素的加入未能破坏ct-DNA的双螺旋结构,两者的作用方式为沟槽结合。进一步通过分子模拟研究得到杨梅素与DNA结合的最低能量构象,杨梅素A环7-O和B环3’-O分别与DNA的碱基DA18和DA6在边缘小沟处通过氢键结合,周围富含碱基A和T,与光谱学研究结果一致,结合距离分别为2.061和1.918。     

荧光光谱和圆二色谱研究重组内皮抑素与芦荟大黄素的相互作用

利用荧光光谱法和圆二色谱法研究了重组内皮抑素与中药有效成分芦荟大黄素的相互作用机制,求得两者在25℃和37℃的结合常数Ka为6.623×104和3.796×104。研究发现,Zn2+等5种金属离子能够竞争性降低重组内皮抑制与芦荟大黄素的结合常数,下降幅度为35%～55%,并且其影响程度随温度升高而增强。鸡胚尿囊膜血管生成实验结果表明,芦荟大黄素能增强重组内皮抑素的抗血管生成活性,使其对新生血管的抑制作用提高50%。     

普利沙星与Co(phen)2+3及DNA间结合作用的电化学和光谱

利用电化学和紫外光谱法研究了邻菲咯啉合钴(Co(phen)2+3)与普利沙星(PLFX)及DNA间在pH=7.4的三羟甲基氨基甲烷-盐酸缓冲溶液中的结合作用. 紫外光谱测量结果表明,普利沙星与Co(phen)2+3发生了结合作用形成二元络合物,结合常数为2.0×104 L/mol. 电化学测量表明,在Co(phen)2+3-普利沙星络合物中加入DNA后,Co(phen)2+3-普利沙星络合物的峰电流下降,峰电位差增大了17 mV,式电位负移了3.5 mV,推断络合物与DNA作用方式主要为静电作用.     

二甲基亚砜及一些含氮环化合物与DNA的作用

通过实验探索了将既不溶于水又不能生成可溶性盐的一些含氮稠环化合物溶于二甲基亚砜（DMSO）水溶液中与小牛胸腺DNA作用的途径．溶解实验证明了DMSO及其水溶液对此类化合物极强的溶解性能，DMSO与小牛胸腺作用的紫外光谱（298 K）、圆二色谱（298 K）、~(31)P核磁谱（323 K）和摩尔焓变（298 K）数据均表明：在pH＝7.0的水溶液中，当DMSO浓度小于0．15 mol·L~(-1)时，其与DNA无作用．溶于DMsO水溶液中的八种含氮稠环化合物与小牛胸腺DNA作用的紫外光谱（298 K）、圆二色谱（298 K）和摩尔焓变（298 K）实验结果显示出两种化合物对DNA有较强的嵌插作用．通过对实验结果的分析，本文对具有相同含氮稠环骨架的化合物与DNA嵌播作用的规律和化合物本身微观结构的关系进行了讨论．     

二甲基亚砜及一些含氮稠环化合物与DNA的作用

A method for studying the effect of some organic compounds, which are neither soluble in water nor to be made into soluble salts in water, on DNA has been investigated by a series of experiments. The solubility experiments have shown that dimethyl sulphoxide (DMSO) and its aqueous solution are excellent solvents for the hydrophobic multicycles compounds with nitrogen atoms. The data of UV (298 K), CD (298 K), ~(31)P-NMR (323 K) spectra and molar enthalpy changes (298 K) for the effect of DMSO on DNA have not shown that DMSO has an effect on DNA when the pH of solution is equal to 7.0 and its concentration is less than 0.15 mol·L~(-1). This has further proved it is safe when DMSO is used as a carrier of medicinal compounds and enters into human bodies. Under the fixed experimental conditions, no differences were found out from the results of viscous tests (298 K) and UV spectra (298 K) for the effect of harmine hydrochloride on DNA in the presence and absence of DMSO even if the concentration of DMSO reached 0.5 mol·L~(-1). It has indicated that the existence of DMSO in aqueous solutions doesn't disturb the effect of compounds on DNA. The data of UV (298 K), CD(298 K), ~(31)P-NMR (323 K) spectra and molar enthalpy changes (298 K) for the effect of some multicycles compounds with nitrogen atoms on DNA in aqueous solutions of DMSO have also given a clear explanation to the intercalation bindings of these organic compounds to DNA, and a method to study the effect of these compounds on DNA can be developed from these experiments. By analying all the data for the effect of the above compounds on DNA, both the mechanism of interaction between the compounds and DNA and the relationship between the rule of intercalation binding of a series of compounds with same multicycles structures to DNA and their microstructures have been discussed. Since the two multicycles compounds with nitrogen atoms including harmine have high bioactivity, the further experiments inside animal bodies and clinical trial on patients as anticancer drugs should be carried out.     

Circular Dichroism Study of the Mechanism of Formation of DNA Templated Nanowires

In order to control the fabrication method, the mechanism used in the formation of DNA templated nanowires is investigated through circular dichroism (CD) spectroscopy. Metallic (Au) and magnetic (Fe₂O₃ and CoFe₂O₄) nanoparticles (NP) are aligned along the DNA strand at various mass ratios. The DNA templated nanowires are compared to the structure of B‐form dsDNA through CD experiments. Absorbance and thermal melting tests are performed to verify the structural changes of DNA templated nanowires. Low concentrations of nanoparticles preserve the DNA B‐form through electrostatic interactions. Conversely, at higher concentrations of nanoparticles aligned along the DNA strand, the template is denatured. Information on the mode of nanoparticle binding and DNA helix alterations are explored for metallic and magnetic nanowires based upon the results.     

Determination of Cordycepin in Cordyceps kyushuensis by Capillary Electrophoresis and its Antitumour Activity

~~Determination of Cordycepin in Cordyceps kyushuensis by Capillary Electrophoresis and its Antitumour Activity~~     

Study of the Interaction of Methylene Violet with Calf Thymus DNA Using an SPR-Based DNA Sensor

Electrochemical and surface plasmon resonance technologies were combined to detect binding of low-molecular-weight compounds to DNA. First, zirconia thin films were electrochemically deposited onto bare gold electrodes. Second, calf thymus DNA was attached onto the zirconia thin films. Finally, the interaction of methylene violet with the DNA-modified surface was tested. The binding isotherm gave a K_D of 2.21 × 10^?5 M. Fluorescence quenching experiments were performed to confirm the interaction. Regenerating surfaces with 1 mM NaOH provided reusable surfaces. This study provides a generic platform which can be tailored for the study of interactions of small molecules with DNA.     

The Exciton Model and the Circular Dichroism of Polypeptides

Summary. Exciton coupling of the 190nm ^* transition is an important factor in the CD spectrum of peptides and proteins. The CD spectrum of the -helix is dominated by the exciton effect. The spectrum is sensitive to the direction of the ^* transition dipole moment, especially for short helices. Exciton theory is much less successful in accounting for the CD spectrum of the poly(proline)II (PPII) conformation, an important conformer in collagen and in unordered peptides. Mixing of the ^* transition with high-energy transitions in the peptide backbone and in side chains must be considered to explain the strong negative CD band near 200nm of PPII.