cis-Diamminodichloronickel and Its Interaction with Guanine and Guanine–Cytosine Base Pair

Comprehensive ab initio calculations are performed on cis-diamminodichloronickel (cisni) at the HF, DFT, and MP2 levels of theory. The results are compared to those obtained for cisplatin. The characteristics of the interactions of cisni with guanine (G) and guanine–cytosine (GC) base pair are also evaluated and compared to the interactions of cisplatin. Cisni causes similar geometric changes of the base as cis-platinum when complexed to guanine. The nickel, palladium and platinum complexes also show similar characteristics when complexed to GC base pair. However, this study predicts higher dissociation energy of the cisni chlorine ligands that indicate areas of differences between the title Ni and Pt and Pd complexes. Comparison of the G-cisni interaction energy to that of cisplatin and cispd indicate differences between the Ni and Pd complexes, but also reveals its closer similarities to cisplatin.     

Microhydration of Guanine base pairs

We report spectroscopy of clusters of guanine base pairs with one and two water molecules. We recorded the vibronic spectra of the mass-selected GG(H2O) and GG(H2O)2 clusters using resonant two photon ionization (R2PI) and we used IR-UV double resonance spectroscopy to obtain ground state IR spectra of these clusters. We found that a single water molecule stabilizes one of two structures we had previously found for guanine dimers. Addition of a second water molecule causes no further structural change.     

Guanine crystals: a first principles study

We report first principles density functional theory studies on the basic ground state characteristics, dynamic properties, and the electronic structure of guanine crystals. The effect of water molecules within the crystal is studied in detail, and we discuss their influence on the structural, vibrational, and electronic properties. The geometries calculated for various crystal structures are compared with gas-phase calculations and available experimental data. Phonon frequencies and eigenvectors are predicted for intermolecular and intramolecular lattice vibrations. Vibrational and electronic density-of-states are presented and analyzed. The electronic band structure near the fundamental gap is calculated from the Kohn-Sham approach. We find that the former molecular HOMO states form a dispersive band in the pi-pi stacking direction upon condensation resulting in a large bandwidth of 0.83 eV. Consequences for the charge transport in layered van der Waals bonded organic molecular crystals are discussed.     

光致电化学鸟嘌呤传感器的制备及其应用

将硫堇电聚合在光透电极的表面,再利用壳聚糖将黄嘌呤氧化酶固定在具有光电活性的聚硫堇光透电极的表面上制备了光致电化学鸟嘌呤传感器.基于同时具有光敏和电子受体功能的聚硫堇光电界面,该传感器能与黄嘌呤氧化酶催化鸟嘌呤氧化而产生的电子供体(过氧化氢)产生光致电化学响应,通过测量光致电化学反应产生的光电流实现了对鸟嘌呤的检测.文中探讨了传感器的光致电化学响应机理,讨论了偏压、酶量、电解质溶液pH对传感器测定鸟嘌呤的影响.在优化的实验条件下,该传感器对鸟嘌呤的测定范围为1.00～200μmol/L,检出限为0.55μmol/L,9次测定的相对标准偏差小于3.92%.应用该传感器对酸解DNA脱出的鸟嘌呤基和药品阿昔洛韦进行的检测实验显示,相对标准偏差小于5.37%,加标回收率为96.8%～106%.该传感器的制备和对鸟嘌呤的检测不需要过氧化物酶,不需要除氧,有经济、简便等优点.     

玻碳电极线扫溶出伏安法测定鸟嘌呤的研究（Ⅰ）

用线扫溶出伏安法和循环伏安法研究了鸟嘌呤在玻碳电极上的电化学行为，鸟嘌呤的阳极锋电流与其浓度在１×１０－７－５×１０－４ｍｏｌ／Ｌ范围内有良好线性关系。讨论了实验条件，建立了测定鸟嘌呤的新分析方法，应用于生物样品中鸟嘌呤的测定，结果满意．     

盐酸鸟嘌呤与牛血清白蛋白的相互作用

应用荧光光谱、紫外-可见分光光度法研究了盐酸鸟嘌呤(GH)与牛血清白蛋白(BSA)的相互作用。结果表明:GH能猝灭BSA的荧光强度,其猝灭机理为静态猝灭。采用位点结合模型公式和热力学公式计算了结合常数、结合位点数及结合类型。用同步荧光技术研究GH对BSA构象的影响。     

Biologically Controlled Morphology and Twinning in Guanine Crystals

Guanine crystals are widely used in nature as components of multilayer reflectors. Guanine‐based reflective systems found in the copepod cuticle and in the mirror of the scallop eye are unique in that the multilayered reflectors are tiled to form a contiguous packed array. In the copepod cuticle, hexagonal crystals are closely packed to produce brilliant colors. In the scallop eye, square crystals are tiled to obtain an image‐forming reflecting mirror. The tiles are about 1 μm in size and 70 nm thick. According to analysis of their electron diffraction patterns, the hexagon and square tiles are not single crystals. Rather, each tile type is a composite of what appears to be three crystalline domains differently oriented and stacked onto one another, achieved through a twice‐repeated twinning about their ⟨011⟩ and ⟨021⟩ crystal axes, respectively. By these means, the monoclinic guanine crystal mimics higher symmetry hexagonal and tetragonal structures to achieve unique morphologies.     

Theoretical Investigation on Interaction between Guanine and Luteolin

The interacting patterns of the luteolin and guanine have been investigated by using the density functional theory B3LYP method with 6-31＋G＊ basis set. Eighteen stable structures for the luteolin-guanine complexes have been found respectively. The results indicate that the complexes are mainly stabilized by the hydrogen bonding interactions. Meanwhile, both the number and strength of hydrogen bond play important roles in determining the stability of the complexes which can form two or more hydrogen bonds. Theories of atoms in molecules and natural bond orbital have also been utilized to investigate the hydrogen bonds involved in all the systems. The interaction energies of all the complexes which were corrected by basis set superposition error are 6.04-56.94 kJ/mol. The calculation results indicate that there are strong hydrogen bonding interactions in the luteolin-guanine complexes. We compared the interaction between luteolin and four bases of DNA, and found luteolin-thymine was the strongest and luteolin-adenine was the weakest. The interaction between luteolin and DNA bases are all stronger than luteolin-water.     

尿素与鸟嘌呤相互作用的DFT研究

采用B3LYP／6—311＋G^＋方法对鸟嘌呤-尿素复合物氢键相互作朋体系进行了研究,并对该复合物的几何构型及结合能（BSSE）进行了计算．此外,采用从静电势导出原子净电荷的chelpg方法分析了体系中的电荷转移和利用分子中的原子理论（AIM）方法对相互作用的本质进行了分析．结果一共得到五个稳定的复合物构型,其中A5是最稳定的,结合能为-73．95kJ／mol．     

Photoinduced Nonadiabatic Dynamics of 9H‐Guanine

Surface‐hopping simulations are used to study the nonradiative relaxation of 9H‐guanine. Two distinct S₁→S₀ (ππ*→gs) decay channels, both of which pass through a conical intersection (CI), are found to be responsible for the experimentally observed double‐decay behavior (see schematic diagram).

     

大白鼠脑组织电极测定鸟嘌呤

以大白鼠脑组织作催化鸟嘌呤脱氨反应的酶源,采用氨气敏电极为基础电极制成测定鸟嘌呤的大白鼠脑组织电极,对其响应特性、介质条件、固定化方法等因素进行了研究,测定鸟嘌呤的E～log[鸟嘌呤]曲线斜率为46.5mV,线性范围2.0×10^-5～6.3×10^-4mol/L,寿命可达28d。     

Synthesis of Bio-Inspired Guanine Microplatelets: Morphological and Crystallographic Control

β-Phase anhydrous guanine (β-AG) crystals are one of the most widespread organic crystals to construct optical structures in organisms. Currently, no synthetic method is available that allows for producing guanine crystals with similar control in size, morphology, and crystallography as in biological ones. Herein, a facile one-step synthesis route to fabricate bio-inspired guanine microplatelets with (100) exposing planes in almost pure β-phase is reported. The synthesis is based on a precipitation process of a guanine sodium hydroxide solution in formamide with poly(1-vinylpyrrolidone-co-vinyl acetate) as a morphological additive. Due to their uniform size (ca. 20 μm) and thickness (ca. 110 nm), the crystals represent the first synthetic guanine microplatelets that exhibit strong structural coloration and pearlescent lusters. Moreover, this synthesis route was utilized as a model system to investigate the effects of guanine analogues, including uric acid, hypoxanthine, xanthine, adenine, and guanosine, during the crystallization process. Our results indicate that the introduction of guanine analogues not only can reduce the required synthesis temperature but also provide a versatile control in crystal morphology and polymorph selection between the α-phase AG (α-AG) and β-AG. Turbidity experiments show that the β-AG microplatelets are formed with a fast precipitation rate in comparison to α-AG, suggesting that the formation of β-AG crystals follows a kinetically driven process.     

Enzymatic Incorporation of a Coumarin–Guanine Base Pair

Previous expansions beyond nature's preferred base‐pairing interactions have utilized either nonpolar shape‐fitting interactions or classical hydrogen bonding. Reported here is a hybrid of these systems. By replacing a single N?H with C?H at a Watson–Crick interface, the design space for new drug candidates and fluorescent nucleobase analogues is dramatically expanded, as demonstrated here by the new, highly fluorescent deoxycytidine mimic 3‐glycosyl‐5‐fluoro‐7‐methoxy‐coumarin‐2′‐deoxyribose (d C ^C ). dGTP is selectively incorporated across from a template d C ^C during enzymatic DNA synthesis. Likewise, d C ^C is selectively incorporated across from a template guanine when d C ^C is provided as the triphosphate d C ^C TP . DNA polymerase I (Klenow fragment) exhibited about a 10‐fold higher affinity for d C ^C TP than dCTP, allowing selective incorporation of d C ^C in direct competition experiments. These results demonstrate that a single C?H can replace N?H at a Watson–Crick‐type interface with preservation of functional selectivity and enhanced activity.