Synthesis and DNA binding properties of pyrrole amino acid-containing peptides

Dimers of the pyrrole amino acid (Paa), 5-(aminomethyl)pyrrole-2-carboxylic acid, and its derivatives having Lys anchored on N- and C-termini bind in the minor groove of DNA with considerable apparent binding affinities. When the Lys unit is attached to the C-terminus, the resulting ligand binds to ds-DNA with twice the affinity, of the order of 10⁵, than the one carrying two positive charges at the same end.     

Chemical modification of polymer surfaces: a review

The main approaches that have been taken to chemically modify polymer surfaces are introduced and reviewed. These are wet chemical oxidation, plasma treatment, classical organic chemistry, and attachment of polymer chains. The extent to which each of these approaches can produce the specific modifications desired is discussed, and any unwanted effects that commonly occur are cited. Finally, the need for using several methods of surface analysis in concert to obtain adequate surface characterization is described.     

配体形状对多吡啶铜(Ⅱ)配合物与DNA作用的影响

合成了一系列含有平面配体的Cu(Ⅱ)多吡啶配合物[Cu(IP)₂]²⁺、[Cu(PIP)₂]²⁺、[Cu(DPPZ)₂]²⁺和[Cu(HPIP)₂]²⁺，用吸收光谱、CD光谱和粘度等方法研究了这些配合物与小牛胸腺DNA的作用。结果表明配体上的取代基及配体的平面性对这些四面体配合物与DNA的结合强弱产生一定的影响。[Cu(DPPZ)₂]²⁺与DNA的结合较强，而[Cu(HPIP)₂]²⁺与DNA的结合较弱。CD光谱显示配合物[Cu(DPPZ)₂]²⁺、[Cu(PIP)₂]²⁺和[Cu(HPIP)₂]²⁺的加入会导致DNA的CD光谱减弱。而[Cu(IP)₂]²⁺的加入则会使DNA的CD光谱增强。同时，[Cu(IP)₂]²⁺与DNA结合后，还会引起一定程度的DNA构型转换，即DNA从B型转换成Z型。     

Characterization of the monovalent ion position and hydrogen-bond network in guanine quartets by DFT calculations of NMR parameters

Conformational stability of G-quartets found in telomeric DNA quadruplex structures requires the coordination of monovalent ions. Here, an extensive Hartree-Fock and density functional theory analysis of the energetically favored position of Li+, Na+, and K+ ions is presented. The calculations show that at quartet-quartet distances observed in DNA quadruplex structures (3.3 A), the Li+ and Na+ ions favor positions of 0.55 and 0.95 A outside the plane of the G-quartet, respectively. The larger K+ ion prefers a central position between successive G-quartets. The energy barrier separating the minima in the quartet-ion-quartet model are much smaller for the Li+ and Na+ ions compared with the K+ ion; this suggests that K+ ions will not move as freely through the central channel of the DNA quadruplex. Spin-spin coupling constants and isotropic chemical shifts in G-quartets extracted from crystal structures of K+- and Na+-coordinated DNA quadruplexes were calculated with B3LYP/6-311G(d). The results show that the sizes of the trans-hydrogen-bond couplings are influenced primarily by the hydrogen bond geometry and only slightly by the presence of the ion. The calculations show that the R(N2N7) distance of the N2-H2...N7 hydrogen bond is characterized by strong correlations to both the chemical shifts of the donor group atoms and the (h2)J(N2N7) couplings. In contrast, weaker correlations between the (h3)J(N1C6') couplings and single geometric factors related to the N1-H1...O6=C6 hydrogen bond are observed. As such, deriving geometric information on the hydrogen bond through the use of trans-hydrogen-bond couplings and chemical shifts is more complex for the N1-H1...O6=C6 hydrogen bond than for the N2-H2...N7 moiety. The computed trans-hydrogen-bond couplings are shown to correlate with the experimentally determined couplings. However, the experimental values do not show such strong geometric dependencies.     

纳米SiO_2颗粒表面修饰的有机分子在介质中的光物理行为研究

利用Sol-Gel方法投篮了单分散性很好的球型二氧化硅纳米颗粒，通过表面化 学修饰法引入了带有荧光发色团的有机分子，通过稳态光物理方法研究了纳米颗粒 表面的有机分子在水、乙醇以及阴、阳离子表面活性剂悬浮液中的光物理行为。实 验表明，纳米颗粒表面有机分子的分散状态是决定其光物理行为的主要因素。这一 结果为设计和开发新型“壳-核”型纳米二氧化硅荧光传感器提供了有用的参考。     

Site-specific modification of the 5"-terminal fragment of PGY1/MDR1 gene mRNA by reactive conjugates of antisense oligonucleotides

The site-specific modification of the 5"-terminal fragment of PGY1/MDR1 mRNA by oligodeoxyribonucleotide conjugates bearing residues of bleomycin A₅ (Blm), cobalt(ii) tetracarboxyphthalocyanine (Phcn), 4-[N-(2-chloroethyl)-N-methylamino]benzylamine (RCl), or perfluoroarylazide (Az) was studied. Conjugates of oligonucleotides complementary to the RNA sequences 123—138 and 155—166 selectively modify RNA in the vicinity of these regions. The highest efficacy (up to 50%) was achieved in reactions with alkylating and perfluoroarylazide conjugates of oligonucleotides. Conjugates of perfluoroarylazide with 2"-O-modified oligonucleotides are much more efficient than analogous conjugates with oligodeoxyribonucleotides (extents of RNA modification are 40—50% and 20%, respectively).     

Design of photoactivated DNA oxidizing agents: synthesis and study of photophysical properties and DNA interactions of novel viologen-linked acridines

A new series of photoactivated DNA oxidizing agents in which an acridine moiety is covalently linked to viologen by an alkylidene spacer was synthesized, and their photophysical properties and interactions with DNA, including DNA cleaving properties, were investigated. The fluorescence quantum yields of the viologen-linked acridines were found to be lower than that of the model compound 9-methylacridine (MA). The changes in free energy for the electron transfer reactions were found to be favorable, and the fluorescence quenching observed in these systems is explained by an electron transfer mechanism. Intramolecular electron transfer rate constants were calculated from the observed fluorescence quantum yields and singlet lifetime of MA and are in the range from 1.06x10(10) s(-1) for 1 a (n=1) to 6x10(8) s(-1) for 1 c (n=11), that is, the rate decreases with increasing spacer length. Nanosecond laser flash photolysis of these systems in aqueous solutions showed no transient absorption, but in the presence of guanosine or calf thymus DNA, transient absorption due to the reduced viologen radical cation was observed. Studies on DNA binding demonstrated that the viologen-linked acridines bind effectively to DNA in both intercalative and electrostatic modes. Results of PM2 DNA cleavage studies indicate that, on photoexcitation, these molecules induce DNA damage that is sensitive to formamidopyrimidine DNA glycosylase. These viologen-linked acridines are quite stable in aqueous solutions and oxidize DNA efficiently and hence can be useful as photoactivated DNA-cleaving agents which function purely by the co-sensitization mechanism.     

磷酸三乙酯改性HZSM-5沸石的活性及理论研究

采用XRD表征了水蒸气和磷联合改性的HZSM-5沸石分子筛的结构．通过NH3-TPD和N2吸附脱附研究了样品的酸性和比表面．采用正庚烷的裂化反应研究了样品的裂化活性，研究结果表明，磷改性样品与母体样品相比，经过水蒸气处理后显示出较高的酸量和正庚烷裂化活性．上述结果首次用模型簇和计算量子化学方法进行了解释．采用Gaussian94软件包和PM3半经验量子化学方法对模型簇进行了全优化和频率分析．计算结果显示磷改性后样品的脱铝补硅反应热大于母体样品脱铝补硅反应热，从而显示出磷对骨架的稳定化作用．     

炭气凝胶及其有机气凝胶前驱体的研究进展

介绍了炭气凝胶及其有机气凝胶前驱体的发展概况，着重总结了制备工艺条件(如催化剂及其浓度、反应物总浓度、反应物配比、溶剂、反应温度及时间、超临界干燥工艺条件和炭化工艺条件等)对有机气凝胶及其相应炭气凝胶中孔网络结构的影响，综述了中孔网络结构改性研究的进展．     

DNA为模板的铂纳米团簇沉积

Platinum nanoclusters were deposited along the supercoiled DNA strands after incubation of cis-(trans-1R，2R-diaminocyclohexane)(dl-camphorato)platinum(Ⅱ) (Cdp)， an analogue of the anti-tumor drug-carboplatin， with DNA and K₂PtCl₄ for 600 min and then through reduction of dimethylaminoborane (DMAB). The decrease of absorption of DNA at 260 nm indicates the coordination of Cdp and DNA. TEM and AFM were employed to characterize the morphologies and structures of platinum nanoclusters.