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Intercalation
Kinds of Intercalation Terms modified by Intercalation Selected AbstractsANTHOCYANIN INTERACTIONS WITH DNA: INTERCALATION, TOPOISOMERASE I INHIBITION AND OXIDATIVE REACTIONSJOURNAL OF FOOD BIOCHEMISTRY, Issue 5 2008MICHAEL R. WEBB ABSTRACT Anthocyanins and their aglycone anthocyanidins are pigmented flavonoids found in significant amounts in many commonly consumed foods. They exhibit a complex chemistry in aqueous solution, which makes it difficult to study their chemistry under physiologic conditions. Here we used a gel electrophoresis assay employing supercoiled DNA plasmid to examine the ability of these compounds (1) to intercalate DNA; (2) to inhibit human topoisomerase I through both inhibition of plasmid relaxation activity (catalytic inhibition) and stabilization of the cleavable DNA,topoisomerase complex (poisoning); and (3) to inhibit or enhance oxidative single-strand DNA nicking. We found no evidence of DNA intercalation by anthocyan(id)ins in the physiologic pH range for any of the compounds used in this study , cyanidin chloride, cyanidin 3- O -glucoside, cyanidin 3,5- O -diglucoside, malvidin 3- O -glucoside and luteolinidin chloride. The anthocyanins inhibited topoisomerase relaxation activity only at high concentrations (>50 µM), and we could find no evidence of topoisomerase I cleavable complex stabilization by these compounds. However, we observed that all of the anthocyan(id)ins used in this study were capable of inducing significant oxidative DNA strand cleavage (nicking) in the presence of 1 mM dithiothreitol, while the free radical scavenger, dimethyl sulfoxide (DMSO), at concentrations typically used in similar studies, completely inhibited DNA nicking. Finally, we proposed a mechanism to explain the anthocyan(id)in-induced oxidative DNA cleavage observed under our experimental conditions. PRACTICAL APPLICATIONS This study provided improved understanding of the mechanisms by which anthocyan(id)ins interact with DNA. By characterizing the chemistry and solution properties of these important dietary components, we obtained improved information on how the anthocyan(id)ins might function in living systems. [source] Divergent and Linear Solid-Phase Synthesis of PNA Containing Thiazole Orange as Artificial BaseEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 15 2005Dilip V. Jarikote Abstract Fluorescent nucleobase surrogates provide nucleic acids with interesting properties. We have recently introduced thiazole orange as base surrogate into PNA and found that the so-called FIT (Forced Intercalation of Thiazole orange) PNA probes signal hybridization by enhancements of fluorescence. Common approaches of modifying nucleobases or introducing nucleobase surrogates draw upon the usage of monomer building blocks that have been synthesized in solution phase. The need to prefabricate a base-modified building block can hold up progress if several base modifications or base surrogates are to be evaluated. Herein, a method for divergent solid-phase synthesis is presented that serves the purpose to facilitate the screening for base surrogates that fluoresce upon hybridization. An Fmoc/Aloc-protected submonomer allowed the application of commonly used Fmoc-based solid-phase synthesis protocols while removal of the fully orthogonal Aloc group enabled the on-resin introduction of base surrogates after the linear chain assembly had been completed. The divergent solid-phase synthesis strategy is automatable, gives overall yields matching those of linear solid-phase synthesis and, most importantly, provides rapid access to any kind of base-modified PNA. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Reduced Surfactant Uptake in Three Dimensional Assemblies of VOx Nanotubes Improves Reversible Li+ Intercalation and Charge CapacityADVANCED FUNCTIONAL MATERIALS, Issue 11 2009Colm O'Dwyer Abstract The relationship between the nanoscale structure of vanadium pentoxide nanotubes and their ability to accommodate Li+ during intercalation/deintercalation is explored. The nanotubes are synthesized using two different precursors through a surfactant-assisted templating method, resulting in standalone VOx (vanadium oxide) nanotubes and also "nano-urchin". Under highly reducing conditions, where the interlaminar uptake of primary alkylamines is maximized, standalone nanotubes exhibit near-perfect scrolled layers and long-range structural order even at the molecular level. Under less reducing conditions, the degree of amine uptake is reduced due to a lower density of V4+ sites and less V2O5 is functionalized with adsorbed alkylammonium cations. This is typical of the nano-urchin structure. High-resolution TEM studies revealed the unique observation of nanometer-scale nanocrystals of pristine unreacted V2O5 throughout the length of the nanotubes in the nano-urchin. Electrochemical intercalation studies revealed that the very well ordered xerogel-based nanotubes exhibit similar specific capacities (235,mA h g,1) to Na+ -exchange nanorolls of VOx (200,mA h g,1). By comparison, the theoretical maximum value is reported to be 240,mA h g,1. The VOTPP-based nanotubes of the nano-urchin 3D assemblies, however, exhibit useful charge capacities exceeding 437,mA h g,1, which is a considerable advance for VOx based nanomaterials and one of the highest known capacities for Li+ intercalated laminar vanadates. [source] Structure and Properties of PHA/Clay Nano-Biocomposites Prepared by Melt IntercalationMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 14 2008Perrine Bordes Abstract PHA-based nano-biocomposites have been prepared by melt intercalation. Two main PHAs, poly(hydroxybutyrate) and poly(hydroxybutyrate -co- hydroxyvalerate) have been studied. Structural characterizations were conducted by advanced techniques like SAXS and TEM. A recent method has determined the degree of clay intercalation and dispersion using solid-state NMR. Well intercalated small tactoids (3,10 layers) homogeneously dispersed into the polymer are obtained when good PHA,clay affinity exists, i.e., with organo-modified MMT. In the case of non-modified MMT, microcomposites are evidenced. Crystallization, mechanical, and thermal properties have been correlated to the materials structures. [source] Intercalation and exfoliation of talc by solid-state shear compounding (S3C) using pan-mill equipmentPOLYMER ENGINEERING & SCIENCE, Issue 4 2005Weiguo Shao The intercalation and exfoliation of talc have been realized by solid-state shear compounding (S3C) using pan-mill equipment that can exert fairly strong shear forces and has multifunctions such as pulverizing, mixing, and activation on materials. The structural features of pan-mill also show prospective in delaminating layered minerals. The morphology and structure of talc were investigated by using transmission electron microscopy (TEM) and X-ray diffraction (XRD). The characteristic peaks of talc interlayer spacing disappeared in the XRD pattern of PP/talc composite prepared by S3C, however, still remained in the XRD pattern of PP/talc prepared by the conventional mixing method. TEM confirms the intercalated and exfoliated structure of talc, and the well dispersion of talc in the PP matrix after talc and PP were co-milled. S3C is a new approach to prepare polymer/layered inorganic filler nanocomposite and has characteristics such as a simple process that needs neither organic ligands nor solvent. POLYM. ENG. SCI. 45:451,457, 2005. © 2005 Society of Plastics Engineers. [source] Intercalation and exfoliation behaviour of clay layers in branched polyol and polyurethane/clay nanocompositesPOLYMER INTERNATIONAL, Issue 2 2006Hesheng Xia Abstract The exfoliation of clay layers was realized in a tri-hydroxyl branched polyether polyol by direct mixing and the corresponding exfoliated polyurethane/clay nanocomposite was prepared by further in situ curing. The effects of various surface-modified organoclays and various polyol types on the intercalation and exfoliation behaviour of clay layers were investigated. The interaction between the polyol and clay and the mixing temperature plays an important role in the occurrence of exfoliation and intercalation. The relationship between rheological data of polyol/clay dispersion and the intercalation or exfoliation state of the clay was established. This provides a convenient and efficient way to evaluate the dispersion state of the clay. Based on the experimental results, a possible layer-by-layer exfoliation mechanism is proposed. Copyright © 2006 Society of Chemical Industry [source] Nanotexture Switching of Single-Layer Hexagonal Boron Nitride on Rhodium by Intercalation of Hydrogen Atoms,ANGEWANDTE CHEMIE, Issue 35 2010Thomas Brugger Dr. Mit H eben, ohne H gewellt: Bei der Behandlung einer Monoschicht aus hexagonalem Bornitrid auf Rhodium mit Wasserstoffatomen verschwindet die h -BN-Oberflächenwellung (siehe Bild: blauer Bereich gewellt, oranger Bereich flach). Diese Veränderung der Oberflächentextur, eine Folge der Interkalation von Wasserstoffatomen, lässt sich rückgängig machen, indem die Wasserstoffatome durch Erhitzen auf etwa 600,K entfernt werden. [source] Lithium Intercalation into Mesoporous Anatase with an Ordered 3D Pore Structure,ANGEWANDTE CHEMIE, Issue 14 2010Yu Ren Überraschendes Anodenmaterial! Mesoporöses Anatas wurde synthetisiert, das eine überlegene Strombelastbarkeit aufweist. Selbst nach 1000 Lade/Entlade-Zyklen mit 12,000,mA,g,1 (1.6,min pro Zyklus) blieb die Mesostruktur mit einer stabilen Kapazität von 125,mA,h,g,1 aufrechterhalten (siehe Diagramm). [source] Thermal stabilization of the DNA duplex by adducts of aflatoxin B1BIOPOLYMERS, Issue 3 2002Indrajit Giri Abstract The trans-8,9-dihydro-8-(N7-guanyl)-9-hydroxyaflatoxin B1 cationic guanine N7 adduct of aflatoxin B1 thermally stabilizes the DNA duplex, as reflected in increased Tm values upon adduction. The magnitude of the increased Tm value is characteristically 2,3°C. The major rotamer of the neutral guanine N7 adduct trans-8,9-dihydro-8-(2,6-diamino-4-oxo-3,4-dihydropyrimid-5-yl-formamido)-9-hydroxy aflatoxin B1 (the FAPY major adduct) exhibits a 15°C increase in Tm in 5,-d(CTATFAPYGATTCA)-3,-5,-d(TGAATCATAG)-3,. Site-specific mutagenesis experiments reveal the FAPY major adduct induces G,T mutations in Escherichia coli at a frequency six times higher than that of the cationic adduct (Smela, M. E.; Hamm, M. L.; Henderson, P. T.; Harris, C. M.; Harris, T. M.; Essigmann, J. M. Proc Natl Acad Sci USA, 99, 6655,6660). Thus, the FAPY major lesion may account substantially for the genotoxicity of AFB1. Structural studies for cationic and FAPY adducts of aflatoxin B1 suggest both adducts intercalate above the 5,-face of the modified deoxyguanosine and that in each instance the aflatoxin moiety spans the DNA helix. Intercalation of the aflatoxin moiety, accompanied by favorable stacking with the neighboring base pairs, is thought to account for the increased thermal stability of the aflatoxin cationic guanine N7 and the FAPY major adducts. However, the structural basis for the large increase in thermal stability of the FAPY major adduct in comparison to the cationic guanine N7 adduct of aflatoxin B1 is not well understood. In light of the site-specific mutagenesis studies, it is of considerable interest. For both adducts, the intercalation structures are similar, although improved stacking with neighboring base pairs is observed for the FAPY major adduct. In addition, the presence of the formamido group in the aflatoxin B1 FAPY major adduct may enhance duplex stability, perhaps via intrastrand sequence-specific hydrogen bonding interactions within the duplex. © 2002 Wiley Periodicals, Inc. Biopolymers (Nucleic Acid Sci) 65: 190,201, 2002 [source] ChemInform Abstract: A Layered Titanium Phosphate Ti2O3 (H2PO4)2·2H2O with Rectangular Morphology: Synthesis, Structure, and Cysteamine Intercalation.CHEMINFORM, Issue 41 2010Laszlo Koroesi Abstract The layered title compound is prepared from a mixture of Ti(OiPr)4, H3PO4, and 2-propanol and characterized by XRD, SEM, and TEM. [source] ChemInform Abstract: Size Control of Catalytic Reaction Space by Intercalation of Alkylcarboxylate Anions into Ni,Zn Mixed Basic Salt Interlayer: Application for Knoevenagel Reaction in Water.CHEMINFORM, Issue 32 2010Takayoshi Hara Abstract The interlayer space of layered Ni-Zn mixed basic salt can be controlled precisely by the intercalation of various carboxylate anions. [source] Nanosize Effect on High-Rate Li-Ion Intercalation in LiCoO2 Electrode.CHEMINFORM, Issue 36 2007Masashi Okubo Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Effect of Indium Intercalation on Various Properties of MoSe2 Single Crystals.CHEMINFORM, Issue 23 2007Aditya M. Vora Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Topotactic Intercalation of a Metallic Dense Host Matrix Chalcogenide with Large Electron,Phonon Coupling: Crystal Structures and Electronic Properties of LixMo2SbS2 (0 , x , 0.7).CHEMINFORM, Issue 15 2007Alexandros Lappas Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Lithium Intercalation into the Titanosilicate Sitinakite.CHEMINFORM, Issue 39 2006Nicholas A. Milne Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Novel 2-Aminothiazonaphthalimides as Visible Light Activatable Photonucleases: Effects of Intercalation, Heterocyclic-Fused Area and Side Chains.CHEMINFORM, Issue 30 2005Zhigang Li Abstract For Abstract see ChemInform Abstract in Full Text. [source] MoS2 Nanostructures: Synthesis and Electrochemical Mg2+ Intercalation.CHEMINFORM, Issue 50 2004Xiao-Lin Li Abstract For Abstract see ChemInform Abstract in Full Text. [source] Sodium Intercalation into the n = 2 Ruddlesden,Popper Type Host Y2Ti2O5S2: Synthesis, Structure, and Properties of ,-NaxY2Ti2O5S2 (0 < x , 1).CHEMINFORM, Issue 10 2004Simon J. Clarke Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Two Alternative Products from the Intercalation of Alkali Metals into Cation-Defective Ruddlesden,Popper Oxysulfides.CHEMINFORM, Issue 4 2002Sophie G. Denis Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Investigation of Yttrium and Polyvalent Ion Intercalation into Nanocrystalline Vanadium Oxide.CHEMINFORM, Issue 45 2001G. G. Amatucci Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Origin of the Metallization of c-Axis Resistivity upon Iodine Intercalation into Bi2Sr2CaCu2O8+,CHEMINFORM, Issue 32 2001Jin-Ho Choy Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] An Aqueous Electrochemical Energy Storage System Based on Doping and Intercalation: Ppy//LiMn2O4,CHEMPHYSCHEM, Issue 16 2008Gaojun Wang Prof. Green energy: An aqueous rechargeable lithium battery (ARLB) based on a doping and intercalation mechanism is presented. This battery is safe, environmentally friendly, and cheap, and could therefore have important applications in new energy storage systems. The new ARLB is composed of polypyrrole and LiMn2O4 electrodes, which are stable and allow a good performance (see voltammograms). [source] Preparation of LLDPE/MgAl-LDH Exfoliation Nanocomposites with Enhanced Thermal Properties by Melt IntercalationCHINESE JOURNAL OF CHEMISTRY, Issue 10 2006Long-Chao Du Abstract The interlayer surface of MgAl layered double hydroxide (MgAl-LDH) was modified by exchanging about half of the interlayer nitrate anions by dodecyl sulfate anions (DS) to get MgAl(H-DS) LDH, and then the MgAl(H-DS) was melt intercalated by LLDPE to get the LLDPE/MgAl-LDH exfoliation nanocomposites. The samples were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), ion chromatography, transmission electron microscopy (TEM), and thermogravimetry analysis (TGA). The nanoscale dispersion of MgAl-LDH layers in the LLDPE matrix was verified by the disappearance of (00l) XRD reflection of the modified MgAl-LDH and by the TEM observation. The TGA profiles of LLDPE/MgAl-LDH nanocomposites show a faster charring process between 210 and 370 °C and a higher thermal stability above 370 °C than LLDPE. The decomposition temperature of the nanocomposites with 10 wt% MgAl(H-DS) can be 42 °C higher than that of LLDPE at 40% weight loss. [source] Polyimide nanocomposites: Comparison of their properties with precursor polymer nanocompositesPOLYMER ENGINEERING & SCIENCE, Issue 12 2001Jin-Hae Chang A precursor poly(amic acid) was obtained by solution polymerization of pyromellitic dianhydride and benzidine in N, N-dimethylacetamide. Poly(amic acid)/Organoclay hybrids were prepared by the solution intercalation method with dodecylamine-montmorillonite. A polyimide hybrid was obtained from poly(amic acid) hybrid by heat treatment at various temperatures. The film type polyimide hybrids showed better thermal properties than poly(amic acid) hybrids. Also, the thermal stability of the two polymer hybrids were enhanced linearly with increasing clay content from 0 to 8 wt%. Tensile properties and gas barriers of the hybrids, however, were enhanced remarkably compared to pristine polymers. Intercalations of the polymer chains in clar were examined through wide angle X-ray diffraction (XRD) and electron microscopy (SEM and TEM). Transmission electron microscopy revealed that a partially exfoliated structure had been obtained from polyimide/organo-clay hybrids. [source] Brachyury -downstream notochord genes and convergent extension in Ciona intestinalis embryosDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 5 2007Kohji Hotta Formation of the chordate body is accomplished by a complex set of morphogenetic movements including convergent extension of notochord cells. In the ascidian Ciona intestinalis, Brachyury plays a key role in the formation of the notochord, and more than 30 Bra-downstream notochord genes have been identified. In the present study, we examined the effects of functional suppression of nine Bra -downstream notochord genes, which include Ci-PTP, Ci-ACL, Ci-prickle, Ci-netrin, Ci-trop, Ci-Noto3, Ci-ASAK, Ci-ERM and Ci-pellino. When the function of the first two genes (Ci-PTP and Ci-ACL) was suppressed with specific morpholinos, the notochord cells failed to converge, while functional suppression of Ci-prickle resulted in a failure of intercalation, and therefore the cells in these three types of embryo remained in the mid-dorsal region of the embryo. Functional suppression of the next four genes (Ci-netrin, Ci-trop, Ci-Noto3 and Ci-ASAK) resulted in the partial defect of intercalation, and the notochord did not consist of a single row. In addition, when the function of the last two genes (Ci-ERM and Ci-pellino) was suppressed, notochord cells failed to elongate in the embryo, even though convergence/extension took place normally. These results indicate that many Bra -downstream notochord genes are involved in convergence/extension of the embryo. [source] Involvement of canonical Wnt/Wingless signaling in the determination of the positional values within the leg segment of the cricket Gryllus bimaculatusDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 2 2007Taro Nakamura The cricket Gryllus bimaculatus is a hemimetabolous insect whose nymphs posses the ability to regenerate amputated legs. Previously, we showed that Gryllus orthologues of Drosophila hedgehog (Gb'hh), wingless (Gb'wg) and decapentaplegic (Gb'dpp) are expressed during leg regeneration and play essential roles in the establishment of the proximal-distal axis. Here, we examined their roles during intercalary regeneration: when a distally amputated tibia with disparate positional values is placed next to a proximally amputated host, intercalary growth occurs in order to regenerate the missing part. In this process, we examined expression patterns of Gb'hh and Gb'wg. We found that expressions of Gb'hh and Gb'wg were induced in a regenerate and the host proximal to the amputated region, but not in the grafted donor distal to the regenerate. This directional induction occurs even in the reversed intercalation. Because these results are consistent with a distal-to-proximal respecification of the regenerate, Gb'wg may be involved in the re-establishment of the positional values in the regenerate. Furthermore, we found that no regeneration occurs when Gb'armadillo (the orthologue of beta-catenin) was knocked down by RNA interference. These results indicate that the canonical Wnt/Wingless signaling pathway is involved in the process of leg regeneration and determination of positional information in the leg segment. [source] Mediolateral intercalation in planarians revealed by grafting experimentsDEVELOPMENTAL DYNAMICS, Issue 2 2003Yumi Saito Abstract We investigated how planarians organize their left,right axis by using ectopic grafting. Planarians have three body axes: anteroposterior (A-P), dorsoventral (D-V), and left,right (L-R). When a small piece is implanted into an ectopic region along the A-P and D-V axes, intercalary structures are always formed to compensate for positional gaps. There are two hypotheses regarding L-R axis formation in this organism: first, that the left and right sides of the animal may be recognized as different parts, and L-R intercalation can induce midline structures (asymmetry hypothesis); second, that both sides may have symmetrical positional values, and mediolateral (M-L) intercalation creates positional values along the L-R axis (symmetry hypothesis). We performed ectopic grafting experiments in the head region of the planarian, Dugesia japonica, to examine these hypotheses. A left lateral fragment containing a left auricle was implanted into the medial region of the host. Ectopic structures were always formed only on the left side of the graft, where lateral tissues abutted onto the medial tissues. However, no morphologic change was induced on the right side of the graft, where left-sided tissues faced onto right-sided tissues. Molecular marker analyses indicated that ectopic structures formed on the left side of the graft were induced by M-L intercalation, supporting the "symmetry hypothesis." When the midline tissues were implanted into a lateral region, they induced a complete ectopic head, demonstrating that M-L intercalation may be sufficient to establish the L-R axis in planarians. Developmental Dynamics 226:334,340, 2003.© 2003 Wiley-Liss, Inc. [source] Square-Wave Voltammetry as a Tool for Investigation of Doxorubicin Interactions with DNA Isolated from Neuroblastoma CellsELECTROANALYSIS, Issue 3-5 2009Dalibor Huska Abstract We investigated ethidium bromide intercalation into DNA molecule as a model system to test square-wave voltammetry (SWV) as a suitable method for this purpose We found that 0.13,,g EtBr intercalates into 1,,g dsDNA in average. Further, SWV was utilized for investigation of doxorubicin-DNA interactions. Intercalated doxorubicin reduced observed dsDNA cytosine and adenine (CA) signal, but also provided new signal called DOXO at ,0.35,V. This phenomenon was observed at both single and double stranded DNA standards. We also employed adsorptive transfer stripping technique coupled with SWV for study of doxorubicin-DNA interactions. Doxorubicin intercalation into dsDNA molecule adsorbed onto working electrode was fast, because we observed considerable changes in CA and DOXO signals after 360,s. Finally, we detected doxorubicin-DNA adducts formed in doxorubicin treated neuroblastoma cells. [source] 4-Aminothiophenol Self-Assembled Monolayer for the Development of a DNA Biosensor Aiming the Detection of Cylindrospermopsin Producing CyanobacteriaELECTROANALYSIS, Issue 22 2008Elisabete Valério Abstract The development of a DNA biosensor for the detection of cylindrospermopsin, based on self-assembled monolayers (SAMs) of 4-aminothiophenol, is investigated. SAMs were characterized by electrochemical reductive desorption. Detection of probe immobilization and hybridization has been achieved by cyclic and square-wave voltammetry (SWV), using methylene blue (MB) as electroactive indicator. The SWV data obtained in phosphate buffer, with and without NaCl, after MB accumulation, revealed an increase of the redox indicator current peaks after the hybridization step. This behavior is consistent with MB intercalation into DNA, for high ionic strength media and attributed to electrostatic interactions in the absence of salt. Evidence for surface modification is also provided by atomic force microscopy and ellipsometry. [source] Fabrication and Characterization of DNA/QPVP-Os Redox-Active Multilayer FilmELECTROANALYSIS, Issue 23 2004Jianyun Liu Abstract Calf thymus DNA was immobilized on functionalized glassy carbon, gold and quartz substrates, respectively, by the layer-by-layer (LBL) assembly method with a polycation QPVP-Os, a quaternized poly(4-vinylpyridine) partially complexed with osmium bis(2,2,-bipyridine) as counterions. UV-visible absorption and surface plasmon resonance spectroscopy (SPR) showed that the resulting film was uniform with the average thickness 3.4,nm for one bilayer. Cyclic voltammetry (CV) showed that the total surface coverage of the polycations increases as each QPVP-Os/DNA bilayer added to the electrode surface, but the surface formal potential of Os-centered redox reaction shifts negatively, which is mainly attributed to the intercalation of redox-active complex to DNA chain. The electron transfer kinetics of electroactive QPVP-Os in the multilayer film was investigated by electrochemical impedance experiment for the first time. The permeability of Fe(CN) in the solution into the multilayer film depends on the number of bilayers in the film. It is worth noting that when the multilayer film is up to 4 bilayers, the CV curves of the multilayer films display the typical characteristic of a microelectrode array. The nanoporous structure of the multilayer film was further confirmed by the surface morphology analysis using atomic force microscopy (AFM). [source] | |||||||||||||||||||||||||||||||||||||