Coulometric redox titrations of some biologically active thiols with iodine in methanol and bromine in acetic acid

The possibility of coulometric titrations of cysteine, 2-thio-uracil, 6-mercaptopurine, and 6-thioguanine with iodine and bromine in methanol and with bromine in acetic acid has been investigated. Conditions have been found for the direct titration of the test substances with iodine in methanol based on their 1-electron oxidation to the corresponding disulphides and for their direct and indirect determination with bromine in acetic acid based on their 6-electron oxidation to the corresponding sulphonic acids.On leave from Department of Analytical Chemistry, Charles University, Prague, Czechoslovakia     

Aluminum Lon Removal from Monoaluminum Ovotransferrin by Pyrophosphate

The rates at which aluminum was removed from the N- and C-terminal monoaluminum ovotransferrins by pyrophosphate were evaluated by UV difference spectra in 0.01 mol/L Hepes, pH=7.4 and at 37℃. Pesudo first-order rate constants as a function of pyrophosphate concentration were measured. The results indicate that the pathways of aluminum removal are different. For the N-terminal binding site, aluminum removal follows simple saturation kinetics, while the removal of aluminum from the C-terminal binding site reverts to the combination of saturation and first-order kinetics. The saturation component is consistent with a rate-limiting conformational change in the protein as has been reported. We propose that the first-order kinetics mechanism is attributed to a pre-equilibrium process. The rate constants of saturation kinetics are accelerated from both terminals with the addition of 0.1 mol/L chloride to the monoaluminum ovotransferrin solutions, whereas the rates of the first-order kinetics are decreased for the C-terminal binding site. The effect of chloride ionic strength causes a continuing increase on kobs for the N- and C-terminal binding sites. Moreover, the kinetics behavior of the N-terminal is more easily affected by chloride than that of the C-terminal. In the experiment presumably the N-terminal site is apparently kinetically more labile than the C-terminal site.     

Electrochemical genosensing properties of gold nanoparticle–carbon nanotube hybrid

We have investigated the electrochemical genosensing properties of gold nanoparticle–carbon nanotube hybrid. Thiolated oligonucleotide probes and mercaptohexanol were self-assembled onto the Au–CNT hybrid. The hybridization events of target oligonucleotides are monitored using electrochemical impedance spectroscopy, cyclic voltammetry and a.c. voltammetry techniques. A redox-active mediator is used to detect the oxidation of guanine residues. The as-fabricated genosensor is able to differentiate between complementary and mismatched hybridizations, relying on the oxidation current of the guanine residues mediated via .     

Nd—Al双金属活性体的组成及其对共轭双烯烃的聚合

稀土Ziegler-Natta催化剂活性体对双烯烃配位聚合的研究已有很多报道。作者曾从NdCl_3·3P_(350)~(**)-Al(i-Bu)_3体系分离出Nd-Al双金属活性体。本文从NdCl_3·3P_(350)-HAl(i-Bu)_2和Al(C_2H_5)_3反应体系中分离出一系列Nd-Al双金属活性体,用元素分析方法研究了这些活性体的组成,并综合考察了在无助催化剂AlR_3存在下从不同烷基铝获得的活性体本身对共轭双烯烃的定向聚合能力。 单体、溶剂、HAl(i-Bu)_2、Al(C_2H_5)_5及活性体的合成,聚合方法,聚合物表征均按文献[4]。     

Encrypting Chemical Reactivity in Protein Sequences toward Information‐Coded Reactions†

Controlling chemical reactivity has been the central theme in chemistry. Herein, we review the recent progress on the development of genetically encoded protein coupling reactions and their potential applications. The chemical reactivity is encoded in the protein sequences. The information is read out by folding and molecular recognition between two reactive components and subsequently translated into chemical bonding via autocatalysis. It has emerged as a unique way to tune the chemical reactivity and is regarded as one type of information‐coded reactions. Not only has it received many applications such as protein topology engineering, bioconjugation, biomaterials and synthetic biology, but also its principle may be extended beyond protein chemistry to enable new modes of supramolecular interactions that promote chemical bonding and that are simultaneously reinforced by covalent bonds.     

Syntheses,structures and electrochemical properties of ruthenium(II/III) complexes with tetradentate Schiff base ligands

Three unsymmetrical tetradentate Schiff base ligands, H₂salipn, H₂salipn-Br₄ and H₂salipn-Cl₂, have been synthesized from the typical condensation reactions of treating 1,2-diaminopropane with salicylaldehyde, 3,5-dibromosalicylaldehyde and 5-chlorosalicylaldehyde, respectively. Treatment of [RuCl₂(PPh₃)₃] with one equivalent of H₂salipn or H₂salipn-Br₄ in the presence of triethylamine in tetrahydrofuran (THF) afforded the corresponding ruthenium(III) complexes [Ru^IIICl(PPh₃)(salipn)] (1) and [Ru^IIICl(PPh₃)(salipn-Br₄)] (2). Interaction of [RuHCl(CO)(PPh₃)₃] with one equivalent of H₂salipn-Cl₂ or H₂salipn-Br₄ under the same conditions led to isolation of ruthenium(II) complexes [Ru^II(CO)(PPh₃)(salalipn-Cl₂)] (3) and [Ru^II(CO)(PPh₃)(salalipn-Br₄)] (4), respectively, in which one of the imine bonds was nucleophilically attacked by hydride to result in the formation of a mixed imine-amine ligand. The molecular structures of 1?1.5CH₂Cl₂, 2, 3?0.5CH₂Cl₂ and 4 have been determined by single-crystal X-ray crystallography. The electrochemical properties of 1–4 were also investigated. Their cyclic voltammograms displayed quasi-reversible Ru(IV)/Ru(III) and Ru(III)/Ru(II) couples with E^o ranging from 0.67 to 1.05 V and 0.74 to 0.80 V vs. Ag/AgCl (0.1 M), respectively.     

Controllable and flexible cellular network for virus cell-to-cell spread

Cellular networks were constructed based on PEG modification and soft lithography, in which cell numbers and spatial distributions can be controlled. A micro-injector was combined with cellular networks to fix virus induced plaque and virus spread direction, by which virus cell-to-cell spread can be distinguished from cell-free spread.     

Sensitive Determination of DNA by Resonance Light Scattering with Pentamethoxyl Red

A novel sensitive method for the determination of nucleic acid (DNA) using the resonance light scattering (RLS) spectra of pentamethoxyl red has been developed. It is based on the effects on the resonance light scattering of Pentamethoxyl Red. The effective factors and the optimum conditions were studied, and the enhanced intensity of RLS is in proportion to the concentration of nucleic acids in the range of 0–2.54 µg mL⁻¹ for ct-DNA, 0–4.54 µg mL⁻¹ for hs-DNA. The limits of detection are 1.1 and 2.1 ng mL⁻¹, respectively. Most foreign substances do not interfere in the determination, and the method has good selectivity and high sensitivity. It has been applied to the determination of DNA in synthetic samples and in real samples with satisfactory results.     

Theoretical study on electronic structure and optical properties of phenothiazine-containing conjugated oligomers and polymers

The application of polyfluorenes in polymeric light-emitting diodes has been hampered because of the charge injection difficulties and the troublesome formation of a tailed emission band at long wavelengths (>500 nm) during device fabrication and operation, leading to both a color instability and reduced efficiency. The incorporation of the phenothiazine units has been proven to significantly enhance the hole injection and charge carrier balance and at the same time efficiently suppress the keto defect emission. In this contribution, we apply quantum-chemical techniques to investigate poly[10-(N-(2'-methyl)phenothiazine-3,7-diyl) and its fluorene copolymer poly[10-(N-(2'-methyl)phenothiazine-3,7-diyl)-co-alt-2,7-(9,9-dimethylfluorene)] (PFPTZ) and gain a detailed understanding the influence of phenothiazine units on the electronic and optical properties of fluorene derivatives. Density functional theory (DFT) and time-dependent DFT approaches are employed to study the neutral molecules, HOMO-LUMO gaps (Delta(H-L)), the lowest excitation energies (E(g)'s), positive and negative ions, as well as the IPs and EAs, focusing on the superiority of the electronic and optical properties attributed to the introduction of electron-donating moiety phenothiazine (PTZ) through comparing with pristine polyfluorene. The outcomes show that the highly nonplanar conformation of phenothiazine ring in the ground state preclude sufficiently close intermolecular interactions essential to forming aggregates or excimers. Furthermore, the HOMO energies lift about 0.4 eV, and thus, the IPs decrease about 0.3 eV in PFPTZ, suggesting the significant improved hole-accepting and transporting abilities, due to the electron-donating properties of phenothiazine ring by the presence of electron-rich sulfur and nitrogen heteroatoms and highly nonplanar characters, resulting in the enhanced performances in both efficiency and brightness compared with pristine polyfluorene. In addition, even though the introduction of electron-donating moiety PTZ onto fluorene leads to a slight bathochromic shift in absorption and emission spectra, the copolymer still exhibited strong blue emission.     

Anderson结构铁钼杂多酸稀土盐的合成与结构表征

制备了具有Anderson结构的铁钼杂多酸稀土盐，经元素组成分析、TG和ICP确定其通式为Ln[FeMo6O24H6](Ln^3 =La，Ce，Pr，Nd，Sm，Gd，Dy，Yb)．采用IR，UV,^95Mo-NMR，XRD等方法进行了结构表征，发现在IR光谱图上呈现出羟基和H2O的两个振动谱带，并进行了归属，表明此类杂多酸稀土盐属Anderson结构B型．借鉴TG-DTA、不同温度下的IR和XRD及水溶性实验对Ln[FeMo6O24H6]和(NH4)3[FeMo6O24H6]的热解性质研究表明，此类杂多酸稀土盐的分解温度为350～400℃．比母体酸盐的热稳定性提高了10℃．