Probing and modulating the interactions of the DNAzyme with DNA-functionalized nanoparticles

DNA-functionalized gold nanoparticles are one of the most versatile bionanomaterials for biomedical and clinical diagnosis. Herein, we discovered that the performance of DNAzyme cleaving the substrate is highly related to its length. This intriguing phenomenon only appears at the interfaces of DNAfunctionalized gold nanoparticles. We systematically investigated the causes of this phenomenon. We conjectured that the DNAzyme with extended nucleotides that do not match its substrate strand is vulne...     

Crystal structures of the complexes of rare earth picrates with N, N, N'''', N''''-tetraphenyl-3, 6-dioxaoctanediamide

The complexes of rare earth picrate with N,N,N',N'-tetraphenyl-3,6-dioxaoctanediamide(TDD),Eu(picc(TDD)] 2CH3CN and [ Y(pic)3(TDD)],have been synthesized.The crystal structures reveal that TDD at is as n tetradentate ligand,forming a ring-like coordination structure with its oxygen atoms together with one oxygen atom of the bidentate pterate In the Eu(Ⅲ) complex,the europium ion with a larger ionic radius lies out of the ring,while in the Y(Ⅲ) complex,the yttrium ion with a smaller ionic radius enters the cavity of the ligand.The structures of the complexes are greatly affected by the ionic radii due to participation of the picrates in coordination.     

Interaction of α,β-Unsaturated Ketones of the Adamantane Series with N,N'-Binucleophiles

The influence has been established of the structure of the initial ketone, the reactants, and the reaction conditions on the direction of the interaction of ,-unsaturated ketones of the adamantane series with hydrazine, phenylhydrazine, semicarbazide, thiosemicarbazide, urea, and thiourea. It was found that on interaction with hydrazine and phenylhydrazine both intermediate hydrazones and the final cyclization products, pyrazolines, were formed. Reaction with semicarbazide and thiosemicarbazide leads only to the synthesis of derivatives at the carbonyl group, semicarbazones and thiosemicarbazones, but with urea and thiourea leads to products of addition at the double bond.     

Features of the reactions of β-aryl(heteryl)-α-nitroacrylates with N,N-, N,O-, and N,S-binucleophiles

The reactions of ??-aryl(heteryl)-??-nitroacrylates with N,N-, N,O-, and N,S-binucleophiles proceed regiospecifically through the initial formation of the Ad_N products, among which only the product from o-aminothiophenol was isolated. The conditions of converting the S-adducts into 2-aryl(heteryl)benzothiazole were found. The N-adducts formed in the reaction with hydrazine, o-phenylenediamine, and o-aminophenol undergo immediately the spontaneous transformation into the linear (azine, azomethine) or heterocyclic (benzimidazole) structures.     

Structure of intermediates in the Hantzsch reaction of phenylchloropyruvic acid derivatives with N,N′-diphenylthiourea

The intermediates in the Hantzsch reaction of the methyl ester and diethylamide of phenylchloropyruvic acid with N,N-diphenylthiourea are derivatives of 2-phenylimino-3,5-diphenyl-4-hydroxythiazoline-4-carboxylic acid. They exist as an equilibrium mixture of two diastereomers in solution.A. E. Arbuzov Institute of Organic and Physical Chemistry of the Kazan Scientific Center, Russian Academy of Sciences, Kazan' 420088; Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 975–980, July, 1999.     

A New Heterocycle from the Reaction of N,N′-Dimethylthiourea with Diamino Phosphinoalkines

Abstract

The reaction of N,N′-dimethylthiourea with bis(dialkylamino)phosphinoalkines proceeds in two steps: 1) a transamination reaction, 2) ring closure by the nucleophilic attack of the sulfur atom at the C°C triple bond.     

Sensitive Spectrophotometric Determination of Benzoylperoxide with N,N,N′,N′-Tetramethyl-p-phenylenediamine

Abstract

A highly sensitive spectrophotometric determination of benzoylperoxide (BPO) based on the color developing reaction between N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD) and BPO in the presence of cerium(IV) in weakly acidic media is proposed. The calibration graph is linear in the range 0–6000 ng BPO per 10 ml with an apparent molar absorptivity of 4.73 × 10⁵ 1 mol^?1 cm-1 at 612 nm. The proposed method is about 50-fold more sensitive than N-ethyl-2-naphthylamine (NENA), and application to assays of flour is described.     

Study on the extraction of trivalent lanthanide ions with N,N′-dimethyl-N,N′-diphenyl-malonamide and diglycolamide

The extraction of trivalent lanthanide (Ln(III) ions with two diamides: (1) N,N′-dimethyl-N,N′-diphenyl-malonamide (MA) and (2) N,N′-dimethyl-N,N′-diphenyl-diglycolamide (DGA) from nitric acid solution was studied. Chemical bond properties of extracted complexes were investigated by UV-VIS and FT-IR spectroscopies. The chemical bond strength between Ln(III) ions and the ligands in extracted complexes was closely related with the magnitude of the distribution ratios of Ln(III) ions: the extracted complex having a stronger bond between Ln(III) ion and the ligand showed a higher magnitude of the distribution ratio of Ln(III) ion.     

Curing of N,N′-diglycidylimides with polyfunctional compounds

This paper describes the curing reactions of new N,N′-diglycidylimides containing trimellitimide units. Reactions were carried out using several polyfunctional curing agents, viz. aromatic primary diamines and phthalic anhydride. Spectroscopic techniques were used to study the curing process. The course of reaction was followed by i.r. spectroscopy. Some intermediate species were detected by recording ¹³C-NMR spectra until the products became insoluble in the usual deuterated solvents.     

Electronic Spectroscopic Studies of the Charge Transfer Complex of N,N , N ′, N ′-Tetramethyl-4-4′-Diamino-Benzophenone with Iodine in Methanol

The UV-visible absorption bands of the charge transfer (CT) complex of N, N, N', N'-tetramethyl-4,4'-diamino-benzophenone with iodine in methanol at 30°C have been studied. The value of K^AD , ?^AD and E _CT were calculated for this complex. The value of the equilibrium constant, K^AD , for the above complex reaction was calculated as 28.85m³·mol^?1. The value of the molar extinction coefficient of the CT complex, ?^AD , was also calculated as 1171m²·mol^?1 for λ_max = 602 nm and the absorption band energy E _CT of the complex was found to be 2.06 e.v. The ionization potential of the electron donor was also obtained spectroscopically and found to be 6.284 e.v. The rate constant obtained for the forward reaction is 3.624 x 10^?5M^1/2s^?1 and for the reverse reaction is 1.256 x 10^?6s^?1. Finally, the half-life value for the above reaction was graphically calculated and shown to be 1.549 day. The kinetics of the above reaction were studied showing the reaction to be a half-order reaction. The values of rate constants and half-life were calculated.     

Networks based on aromatic glycidylamines: 1. Effect of curing conditions on the crosslinking of N,N-diglycidylaniline with 4,4′-diaminodiphenylmethane and of N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenylmethane with 4,4′-diaminodiphenylmethane

The effect of time and temperature of curing on the conversion of epoxy groups, on the relative change of some other functional groups (–OH, –NH₂, RNH), glass transition temperatureT _g , and equilibrium modulusG _e was investigated for epoxy networks having various initial ratios of N,N-diglycidylaniline to 4,4-diaminodiphenylmethane (DDM) and of networks with various ratio of N,N,N,N-tetraglycidyl-4,4-diaminodiphenylmethane and DDM. Curing conditions were found under which the conversion of minority groups is maximal at the minimal extent of degradation reactions for networks prepared both in the excess of amine and in the excess of epoxide. For networks prepared in the excess of epoxide the degree of the etherification reaction was found to depend on time and temperature.     

Thermodynamic characteristics of the protolytic equilibria of tetramethylenediamine-N,N,N′,N′-tetraacetic acid

The stepwise dissociation constants of tetramethylenediamine-N,N,N′,N′-tetraacetic acid (H₄L) are determined by means of potentiometry at 298.15 K and ionic strength values of 0.1, 0.5, and 1.0 (KNO₃). The heat effects of the dissociation of the betaine groups of the complexone are measured by direct calorimetry. The standard thermodynamic characteristics of the protolytic equilibria of H₄L are calculated via combined use of the results from thermochemical and potentiometric studies performed under identical experimental conditions. Our results are compared with the corresponding data on relative compounds.     

Calorimetric study of the solubilization of ethylenediamine,N,N-dimethylaminoethylamine and N,N,N′,N′-tetramethylethylenediamine by reversed AOT micelles

Distribution constants and standard enthalpies of transfer of ethylenediamine (en), N,N-dimethylaminoethylamine (dmen) and N,N,N,N-tetramethylethylenediamine (tmen) partitioned between n-heptane and water containing reversed sodium bis(2-ethylhexyl) sulfosuccinate (AOT) micelles as a function of the molar concentration ratio R (R=[water]/[AOT]) were evaluated by a calorimetric method. The results show that en, dmen and tmen molecules, solubilized in the reversed micelles, are distributed between the micellar aqueous core and the micellar palisade layer. An analysis of the thermodynamic parameters of the partition process demonstrates the peculiar solvent properties of the water containing reversed AOT micelles.     

Static Dielectric Constants and Kirkwood Correlation Factor of the Binary Mixtures of N-Methylformamide with Formamide,N,N-Dimethylformamide and N,N-Dimethylacetamide

Static dielectric constant values of the binary mixtures of N-methylformamide with formamide, N,N-dimethylformamide and N,N-dimethylacetamide have been measured in the whole composition range at 303 K. The Kirkwood correlation factor values of the amide–amide mixtures were determined from the measured values of the static dielectric constant and high-frequency limit dielectric constant. The evaluated values of the excess dielectric constant and deviation in the Kirkwood correlation factor infer that deviations of their mixture values occur from the mole-fraction mixture law. Results confirm that there are strong hydrogen-bond interactions between unlike molecules of amide–amide mixtures and that 1:1 complexes are formed.     

Crystal Structure of the Addition Compound of N,N′-Bi(2-pyridylmethyl)-Oxamide and the Complex of Copper with 1,10-Phenanthroline

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The structure effect of N,N,N′,N′-alkylamide in the extraction of uranium and thorium

In this paper, nine N,N,N,N-tetraalkyldiamides have been synthesized and the extracting ability for uranium and thorium under different conditions has been studied. All results were compared with those obtained by using tributyl phosphate (TBP) under exactly the same conditions. The extracting ability of thorium and uranium for different N,N,N,N-tetraalkyldiamides is discussed.     

On the properties of X···N noncovalent interactions for first-, second-, and third-row X atoms

In addition to a structure with a PH···N H-bond, a second complex of greater stability is formed when the PH(3) is rotated such that its P-H bond is pointing away from the approaching N lone pair of NH(3). Quantum calculations are applied to examine whether such a complex is characteristic only of P, or may occur as well for other atoms of the first, second, or third rows of the periodic table. The molecules PH(3), H(2)S, HCl, AsH(3), and NH(3) are all paired with NH(3) as electron donor. While NH(3) will not engage in an N···N attraction, all the others do form a X···N complex. The energetics, geometries, and other properties of these complexes are relatively insensitive to the nature of the X atom. This uniformity contrasts sharply with the H-bonded XH···N complexes where a strong sensitivity to X is observed. The three-dimensional nature of the electrostatic potential, in conjunction with the striving for a linear H-X···N orientation that maximizes charge transfer, serves as an excellent tool in understanding both the shape of the potential energy surface and the proclivity to engage in a X···N interaction.     

Reactions of N-Allyl- and N-Propargyltriflimides with N,N′-Disubstituted Carbodiimides

The alkylating activity of N-allyl- and N-propargyltriflimides toward N,N′-dicyclohexyl- and N,N′-diphenylcarbodiimides has been studied. Activation of the nitrogen atom by two electron-withdrawing trifluoromethanesulfonyl groups favors cleavage of the C–N bond in the absence of a catalyst with the formation of N-substituted unsaturated ureas.

     

Spectrophotometric Method for the Determination of Cobalt with N,N′-Bis(2-Aminobenzoyl)Ethylenediamine

 A simple and direct spectrophotometric method has been developed for the determination of cobalt(II) using N,N′-Bis(2-aminobenzoyl)ethylenediamine (Baben). The method is based on the colour reaction between Baben and cobalt(II) in borax buffer (pH 9.2). The studies are carried out at 470 nm at which the calculated value of molar absorptivity is found to be 1.102 × 10⁴ L mol⁻¹ cm⁻¹. The system obeys Beer’s law over a wide range of concentration (2–20 μg/ml). The effect of interfering ions has been studied and the method was applied to the determination of cobalt in water, industrial effluents and in alloys and the results were highly satisfactory. Received May 8, 2000. Revision January 30, 2001.