Matroid Shellability, β-Systems,and Affine Hyperplane Arrangements

The broken-circuit complex is fundamental to the shellability and homology of matroids, geometric lattices, and linear hyperplane arrangements. This paper introduces and studies the -system of a matroid, nbc(M), whose cardinality is Crapo's -invariant. In studying the shellability and homology of base-pointed matroids, geometric semilattices, and afflne hyperplane arrangements, it is found that the -system acts as the afflne counterpart to the broken-circuit complex. In particular, it is shown that the -system indexes the homology facets for the lexicographic shelling of the reduced broken-circuit complex , and the basic cycles are explicitly constructed. Similarly, an EL-shelling for the geometric semilattice associated with M is produced,_and it is shown that the -system labels its decreasing chains.Basic cycles can be carried over from The intersection poset of any (real or complex) afflnehyperplane arrangement is a geometric semilattice. Thus the construction yields a set of basic cycles, indexed by nbc(M), for the union of such an arrangement.     

Supramolecular Hybrids from Cyanometallate Complexes and Diblock Copolypeptide Amphiphiles in Water

The self-assembly of discrete cyanometallates has attracted significant interest due to the potential of these materials to undergo soft metallophilic interactions as well as their optical properties. Diblock copolypeptide amphiphiles have also been investigated concerning their capacity for self-assembly into morphologies such as nanostructures. The present work combined these two concepts by examining supramolecular hybrids comprising cyanometallates with diblock copolypeptide amphiphiles in aqueous solutions. Discrete cyanometallates such as [Au(CN)₂]⁻, [Ag(CN)₂]⁻, and [Pt(CN)₄]²⁻ dispersed at the molecular level in water cannot interact with each other at low concentrations. However, the results of this work demonstrate that the addition of diblock copolypeptide amphiphiles such as poly-(L-lysine)-block-(L-cysteine) (Lys_m-b-Cys_n) to solutions of these complexes induces the supramolecular assembly of the discrete cyanometallates, resulting in photoluminescence originating from multinuclear complexes with metal-metal interactions. Electron microscopy images confirmed the formation of nanostructures of several hundred nanometers in size that grew to form advanced nanoarchitectures, including those resembling the original nanostructures. This concept of combining diblock copolypeptide amphiphiles with discrete cyanometallates allows the design of flexible and functional supramolecular hybrid systems in water.     

Mixed-Valent Trinuclear CoIII-CoII-CoIII Complex with 1,3-Bis(5-chlorosalicylideneamino)-2-propanol

A mixed-valent trinuclear complex with 1,3-bis(5-chlorosalicylideneamino)-2-propanol (H₃clsalpr) was synthesized, and the crystal structure was determined by the single-crystal X-ray diffraction method at 90 K. The molecule is a trinuclear Co^III-Co^II-Co^III complex with octahedral geometries, having a tetradentate chelate of the Schiff-base ligand, bridging acetate, monodentate acetate coordination to each terminal Co³⁺ ion and four bridging phenoxido-oxygen of two Schiff-base ligands, and two bridging acetate-oxygen atoms for the central Co²⁺ ion. The electronic spectral feature is consistent with the mixed valent Co^III-Co^II-Co^III. Variable-temperature magnetic susceptibility data could be analyzed by consideration of the axial distortion of the central Co²⁺ ion with the parameters Δ = –254 cm⁻¹, λ = –58 cm⁻¹, κ = 0.93, tip = 0.00436 cm³ mol⁻¹, θ = –0.469 K, g_z = 6.90, and g_x = 2.64, in accordance with a large anisotropy. The cyclic voltammogram showed an irreversible reduction wave at approximately −1.2 V·vs. Fc/Fc⁺, assignable to the reduction of the terminal Co³⁺ ions.     

Discriminating between Parallel,Anti-Parallel and Hybrid G-Quadruplexes: Mechanistic Details on Their Binding to Small Molecules

G-quadruplexes (G4) are now extensively recognised as a peculiar non-canonical DNA geometry that plays a prime importance role in processes of biological relevance whose number is increasing continuously. The same is true for the less-studied RNA G4 counterpart. G4s are stable structures; however, their geometrical parameters may be finely tuned not only by the presence of particular sequences of nucleotides but also by the salt content of the medium or by a small molecule that may act as a peculiar topology inducer. As far as the interest in G4s increases and our knowledge of these species deepens, researchers do not only verify the G4s binding by small molecules and the subsequent G4 stabilisation. The most innovative studies now aim to elucidate the mechanistic details of the interaction and the ability of a target species (drug) to bind only to a peculiar G4 geometry. In this focused review, we survey the advances in the studies of the binding of small molecules of medical interest to G4s, with particular attention to the ability of these species to bind differently (intercalation, lateral binding or sitting atop) to different G4 topologies (parallel, anti-parallel or hybrid structures). Some species, given the very high affinity with some peculiar G4 topology, can first bind to a less favourable geometry and then induce its conversion. This aspect is also considered.     

SiO2包覆铕(Ⅲ)配合物的荧光纳米粒子合成与性质

以前驱物pAB-DTPAA-APTEOS、正硅酸乙酯(TEOS)和三氯化铕(EuCl3)等为原料,采用油包水(W/O)的反相微乳液法,在正硅酸乙酯(TEOS)和3-氨丙基三乙氧基硅烷(APTEOS)的共同水解下,制备出新型的SiO2包覆铕配合物荧光纳米粒子Eu-pAB-DTPAA-AP-SiO2。运用TEM、IR、UV-Vis、荧光光谱等技术对荧光纳米粒子进行了表征。TEM结果表明:包覆体呈球形,分散均匀,平均粒径为40nm。纳米粒子与配体、前驱物的紫外吸收谱相比较,峰位发生了一定的红移,表明通过反相微乳液法得到的固体粉末与EuCl3反应后,已经生成配合物Eu-pAB-DTPAA-AP-SiO2。红外光谱研究表明,在801cm-1出现νSi—C的伸缩振动峰,471cm-1处出现νEu—O的伸缩振动峰。由此证实Eu-pAB-DTPAA-AP-SiO2配合物的存在。荧光光谱分析表明,纳米粒子Eu-pAB-DTPAA-AP-SiO2表现出较好的荧光性能,位于592,615,689nm的发射峰分别归属于Eu3 离子的5D0→7F1、5D0→7F2和5D0→7F4跃迁,其中最强峰615nm属于Eu3 的特征跃迁发射。作为一种新型的荧光试剂,该纳米粒子具有粒径小,亲水性强,荧光强度大,且表面的氨基能方便地与生物分子偶联,故可作为优良的时间分辨荧光标记物用于各种高灵敏生物检测技术中。     

Oxidation of Styrene to Benzaldehyde Catalyzed by Schiff Base Functionalized Triazolylidene Ni(II) Complexes

Four new Schiff base functionalized 1,2,3-triazolylidene nickel complexes, [Ni-(L₁NHC)₂](PF₆)₂; 3, [Ni-(L₂NHC)₂](PF₆)₂; 4, [Ni-(L₃NHC)](PF₆)₂; 7 and [Ni-(L₄NHC)](PF₆)₂; 8, (where L₁NHC = (E)-3-methyl-1-propyl-4-(2-(((2-(pyridin-2-yl)ethyl)imino)methyl)phenyl)-1H-1,2,3-triazol-3-ium hexafluorophosphate(V), 1, L₂NHC = (E)-3-methyl-4-(2-((phenethylimino)methyl)phenyl)-1-propyl-1H-1,2,3-triazol-3-ium hexafluorophosphate(V), 2, L₃NHC = 4,4′-(((1E)-(ethane-1,2-diylbis(azanylylidene))bis(methanylylidene))bis(2,1-phenylene))bis(3-methyl-1-propyl-1H-1,2,3-triazol-3-ium) hexafluorophosphate(V), 5, and L₄NHC = 4,4′-(((1E)-(butane-1,4-diylbis(azanylylidene))bis(methanylylidene))bis(2,1-phenylene))bis(3-methyl-1-propyl-1H-1,2,3-triazol-3-ium) hexafluorophosphate(V), 6), were synthesised and characterised by a variety of spectroscopic methods. Square planar geometry was proposed for all the nickel complexes. The catalytic potential of the complexes was explored in the oxidation of styrene to benzaldehyde, using hydrogen peroxide as a green oxidant in the presence of acetonitrile at 80 °C. All complexes showed good catalytic activity with high selectivity to benzaldehyde. Complex 3 gave a conversion of 88% and a selectivity of 70% to benzaldehyde in 6 h. However, complexes 4 and 7–8 gave lower conversions of 48–74% but with higher (up to 90%) selectivity to benzaldehyde. Results from kinetics studies determined the activation energy for the catalytic oxidation reaction as 65 ± 3 kJ/mol, first order in catalyst and fractional order in the oxidant. Results from UV-visible and CV studies of the catalytic activity of the Ni-triazolylidene complexes on styrene oxidation did not indicate any clear possibility of generation of a Ni(II) to Ni(III) catalytic cycle.     

带-NH2的嘧啶环对钌配合物与DNA相互作用的瞬态发光特性的影响

采用时间分辨的发光光谱技术,分别测量了两种新合成的钌配合物[Ru(bpy)2 (dpbpd(NH2)2)]2 和[Ru(phen)2(dpbpd(NH2)2)]2 与小牛胸腺脱氧核糖核酸(ctDNA)相互作用时的瞬态发光动力学过程,并与以往对[Ru(phen)2dppz]2 等的研究结果进行对比,从而研究带-NH2的嘧啶环对配合物与DNA作用动力学过程的影响.结果表明:这两种含有带-NH2的嘧啶环的钌配合物与DNA相互作用时的发光按双指数规律衰减,发光寿命为几十纳秒,比dppz类钌配合物与DNA作用时的发光衰变寿命(几百纳秒)小一个数量级.归因于嘧啶环上的N和-NH2可能与水分子、DNA的碱基对或磷酸骨架形成氢键,从而加快激发态的无辐射弛豫,削弱发射光强,缩短发光寿命.该结论为进一步研究配合物分子与DNA的相互作用的机理提供了一定的依据.     

Complex Behaviors of a Simple Traffic Model

In this paper, we propose a modified traffic model in which a single car moves through a sequence of traffic lights controlled by a step function instead of a sine function. In contrast to the previous work [Phys. Rev. E 70 (2004)016107], we have investigated in detail the dependence of the behavior on four parameters, ω, α, η, and a1, and given three kinds of bifurcation diagrams, which show three kinds of complex behaviors. We have found that in this model there are chaotic and complex periodic motions, as well as special singularities. We have also analyzed the characteristic of the complex period motion and the essential feature of the singularity.     

一例含阴离子水簇的钴配合物的合成、结构及理论研究

金属配合物中的水簇研究为研究宏观意义上的水以及与蛋白质分子有关的水分子提供了有效途径。本文合成了一个含有阴离子水簇的带状超分子配合物[Co(2,2-bipy)₂(N₃)₂](N₃)_0.5Cl_0.5·2H₂O(1,2, 2-bipy=2, 2-联吡啶)。单晶结构解析表明,配合物属于三斜晶系,P-1空间群,晶胞参数为:a=0.822 54(7) nm,b=1.175 58(9) nm,c=1.237 06(10) nm,α=91.379 0(10)°,β=92.151 0(10)°,γ=108.119 0(10)°,V=1.135 27(16) nm³,由一个单核[Co(2,2-bipy)₂(N₃)₂]⁺配合物阳离子、两个非配位水分子、0.5个游离的叠氮离子和0.5个氯离子组成,叠氮离子和氯离子位置无序,占有率各为50%。两个客体水分子通过强烈的分子间氢键作用形成了环状水四聚体,且与无序的N^-₃和Cl^-通过氢键作用形成了一个[(H₂O)₄(N₃)Cl]^2- 阴离子水簇。此外,本文基于密度泛函理论(DFT)对配合物[Co(2,2-bipy)₂(N₃)₂]⁺阳离子进行了量子化学计算,分析了其单点能和原子电荷,并计算了中心金属离子的氧化态,计算结果与实验相吻合。     

电化学方法研究(phen)2Cu2+配合物与DNA的相互作用

用电化学循环伏安法和微分脉冲伏安法研究了1,10-邻菲咯啉铜配合物[（phen）2Cu^2＋]与小牛胸腺DNA（CTDNA）的相互作用。结果发现,在pH=7．4的三羟甲基胺基甲烷-盐酸缓冲溶液（Tris—HCl）中,（phen）2Cu^2＋配合物的铜离子在循环伏安图上呈现明显的准可逆氧化-还原波。当加入一定量的小牛胸腺DNA时,配合物（phen）,Cu^2＋的氧化和还原峰电流均有所下降。通过比较（phen）2Cu^2＋配合物中加入单链DNA和双链DNA后的氧化和还原峰电流下降的程度,前者比后者F降的程度小,可以得出（phen）2Cu^2＋配合物与小牛胸腺双链DNA的作用方式存在着插入式的沟槽结合模式。这个结论在本实验中由盐效应进一步得到证实。由此可知,（phen）2Cu^2＋配合物与小牛胸腺DNA形成了一种插入式的电惰性结合物,从而导致氧化还原峰电流下降。