甲醇和氨对腺嘌呤水解脱氨机理的影响(英文)

用密度泛函理论在B3LYP/6-311G(d,p)水平上研究了甲醇和氨辅助的腺嘌呤水解脱氨机理,结果表明该反应首先是在水的亲核进攻下形成一个四面体结构中间体,然后该中间体通过构象变化得到两个不同构象,从而找到两条不同反应路径.在路径a中,辅助分子参与了过渡态的形成,起到转移氢原子的作用;而在路径b中,辅助分子仅作为介质,没有参与过渡态的形成.在氨辅助的情况下,腺嘌呤在亲核反应前发生了胺-亚胺异构化,而在甲醇辅助机理中则未发生该异构化.能量结果表明甲醇辅助腺嘌呤脱氨反应具有与水辅助类似的势垒,而氨辅助反应的势垒则比水辅助的高.     

铜的腺嘌呤络合物在悬汞电极表面上的吸附形态和氧化还原行为

本文详细地研究了铜的腺嘌呤（Ａｄｅ）络合物在悬汞电极（ＨＭＤＥ）表面上的吸附形态和伏安行为。实验结果揭示了单层吸附饱和之前有Ｃｕ＾＋Ａｄｅ，Ｃｕ２＾＋（Ａｄｅ）２形态的共吸附作用，随着电极表面的吸附浓度增长，Ａｄｅ络合物分子有从平面向垂直吸附的定向作用。哦的多层吸附和聚合作用发生在吸附分子垂直定向以后。本文还测定了有关电极过程的动力学参数。     

Electrochemical Detection of Abasic Site‐Containing DNA

A simple and rapid approach for detecting apurinic (AP) sites in DNA, based on direct stripping chronopotentiometric measurements of the adenine and guanine nucleobases at a graphite electrode is described. Tetrahydrofuranyl residues, lacking a nucleobase moiety, were utilized for designing the AP sites and were incorporated in 19‐mer oligonucleotides. The change of adenine‐to‐guanine response ratio (A/G) in one‐, two‐ or three‐substituted adenosine residues for stable analogs of AP sites was exploited for electrochemical measurements of the adenine loss. The resulting A/G response ratio decreases linearly upon increasing the number of AP sites in the oligonucleotides; the values of A/G electrochemical signals were slightly enhanced when compared to the actual purine content. HPLC analysis of the released nucleobases confirmed that the sulfuric acid‐induced oligonucleotide cleavage provides complete apurination and dissolution of the released nucleobases in aqueous solution. Additional experiments with mixtures of free nucleobases and purine nucleosides reveal that the larger A/G ratio observed in the electrochemical analysis of AP‐site‐containing oligomers is attributed to the influence of the acid and/or thermal decomposition products (particularly the sugar fragments). This study represents the first step in developing a simple and direct electrochemical assay of AP sites in single‐stranded DNA.     

Solubility of Adenine and Kinetin in Water–Ethanol Solutions

We have measured the solubility of adenine and kinetin in water–ethanol solutions. Various models of cosolvency have been taken into account in the analysis of the experimental data. The results are interpreted in terms of hydrophobic interactions.     

The adsorption of adenine on mineral surfaces: Iron pyrite and silicon dioxide

The adsorption of the nucleobase adenine on surfaces of the minerals iron pyrite and silica has been studied by photoemission and soft X-ray photoabsorption spectroscopy. Pyrite samples were prepared by fracture under nitrogen followed by transfer to ultrahigh vacuum, or by cleavage in vacuum. By comparing data with multilayer spectra, adenine was found to chemisorb on pyrite, with small changes in the valence band spectrum, and stronger changes in the NEXAFS spectrum. The molecules were bonded with the molecular plane at a steep angle to the surface plane. On silica the molecule was found to adsorb at a reduced angle to the surface. The C and N 1s photoemission spectra on this surface suggest chemisorption, although the nitrogen NEXAFS spectra are similar to multilayer spectra.     

胶束毛细管电动色谱法用于DNA碱基腺嘌呤和嘌呤类抗癌药物的研究

腺嘌呤（ADE）是存在于自然界的DNA碱基之一,8-羟基嘌呤（8-HP）是DNA中氧化损伤产物,6-巯基嘌呤（6-MCP）和8-氮杂鸟嘌呤（8-AZN）都属于核酸代谢拮抗药物,该药主要用于治疗急性白血病,对慢性颗粒细胞白血病及其它多种肿瘤也较有效,能在一个体系里同时检测正常DNA碱基、DNA中氧化损伤产物和抑制DNA损伤的抗癌药物,     

取代基对腺嘌呤与胸腺嘧啶氢键复合物体系结合能的影响

优化得到了17个取代胸腺嘧啶与腺嘌呤形成的氢键复合物的结构, 并计算了这些复合物的结合能, 探讨了胸腺嘧啶上不同取代基对结合能的影响. 结果表明, CF₃取代的胸腺嘧啶与腺嘌呤间的结合能大于胸腺嘧啶与腺嘌呤间的结合能, 这可能是屈氟尿苷具有阻止病毒及肿瘤扩散功能的原因所在. SO₃H, CN和NO₂取代的胸腺嘧啶与腺嘌呤间具有更大的结合能, 表明这3个基团取代的胸腺嘧啶也可能具有潜在的抗肿瘤作用. 分子中原子理论与自然键轨道分析表明, 在所有体系中, 氢键N—H…N最强, N—H…O=C次之, C—H…O=C最弱, 轨道作用在氢键作用中占有重要地位.     

小鼠肝组织中单胺氧化酶碱解产物(次黄嘌呤、腺嘌呤)的高效液相色谱分析

用HPLC法检测小鼠肝组织中单胺氧化酶碱解产物(次黄瞟呤、腺嘌呤)方法。该方法快速简单,提取样品所用缓冲溶液KOH-KHPO_4(pH=7.2)为最佳。碱解量KOH 2ml,温度36℃,时闻24h,所用色谱条件为: HPLC柱C_(18) 4.6mm×25cm 5μm,流动相为)甲醇:水10:90(V/V,检测波长249nm,灵敏度0.05AuFs,该方法只需12min将完成一次色谱分析。     

Liquid Chromatographic Determination of Four Purine Bases Using Porous Graphitic Carbon Column

A high performance liquid chromatographic method has been developed for the simultaneous determination of hypoxanthine (Hx), xanthine (Xa), guanine (Gu) and adenine (Ad) in shellfish. The separation of these compounds was performed on a porous graphitic carbon column (100 × 4.6 mm I.D.) using acetonitrile-phosphate buffer (23/77 v/v) containing 0.5% trichloroacetic acid at pH 2.0 as the mobile phase. The flow rate was fixed to 1 mLmin^–1 and the detection was monitored at 254 nm. Calibration curves were found to be linear in the concentration range from 0.3 to 100 gmL^–1 with correlation coefficients (r²) > 0.999. The lowest detectable concentrations of Hx, Xa, Gu and Ad were 0.04, 0.06, 0.08, 0.07 g mL^–1 respectively. Recovery of all purine standards added to sea urchin gonad was above 97%. The proposed method was successfully applied for the determination of Hx, Xa, Gu and Ad in sea urchin gonad extract.     

pH dependent interaction of biofunctionalized CdS nanoparticles with nucleobases and nucleotides: A fluorimetric study

The interaction of DNA bases and corresponding nucleotides with CdS nanoparticles (NPs), biofunctionalized by cysteine, has been investigated by absorption and fluorescence spectroscopy. Unique enhancement effect of adenine, in contrast to other nucleobases, on the luminescence of cysteine capped CdS (cys-CdS) NPs at both pH 7.5 and 10.5 was found, the extent of enhancement being much higher at pH 10.5. At the latter pH, the difference optical absorption spectra show development of new peak at 278 nm with corresponding decrease in the absorption of adenine at 260 nm, which is attributed to binding of adenine anion to the CdS surface through N7 of the purine ring. Appearance of a new band at 478 cm⁻¹ and concomitant shift in the C₈-N₇ vibrations to 1610 cm⁻¹ in the FTIR spectra of cys-CdS NPs with adenine also suggest Cd-N7 binding on the particle surface. Amongst various nucleotides, ATP exhibited maximum luminescence enhancement on CdS NPs for a given change in concentration in the micro-molar range at physiological pH. A quantitative correlation between ATP concentration and PL enhancement of CdS NPs has been established, a step which in future might assist in developing new protocols for fluorescence sensing of adenine nucleotides under certain pathological conditions.