Kinetics and mechanism of the complexation and anation of protonated dioxotetracyanomolybdate(IV) with 1,10-phenanthroline

The anation kinetics of the protonated dioxotetracyanomolybdate(IV) ion with 1,10-phenanthroline have been studied spectrophotometrically. The effect of the H+ ion, ionic strength and temperature on the reaction rate has been determined; the rate increases with increasing H+ ion concentration, is independent of ionic strength, and increases with temperature. The reaction follows first order kinetics with respect to [Mo(OH)2- (H2O)2(CN)4]2– and is considered to proceed through the formation of a 1,10-phenanthroline–Mo(OH)2- (H2O)2(CN)4M2– complex (outer sphere) which converts into an inner sphere complex. The formation constant (Kn) for the outer sphere complex has been calculated from the kinetic data by two different methods. Anation of Mo(OH)2-(H2O)2(CN)42– is discussed in terms of an associative interchange (Ia) mechanism. The activation parameters have been calculated using the Arrhenius equation. A substitution mechanism is proposed and the rate equation derived:kobs = kKnKa[H+] [phen] /{1 + KnKa[H+] [phen]}.     

Controlled fabrication of 1D molecular lines across the dimer rows on the Si(100)-(2 x 1)-H surface through the radical chain reaction

Current interest in the fabrication of organic nanostructures on silicon surface is focused on the self-directed growth of 1D molecular lines with predefined position, structure, composition, and the length on the H-terminated Si(100)-(2 x 1) surface. To date, no studies have succeeded in growing the molecular line across the dimer rows on Si(100)-(2 x 1)-H, which is highly desirable. Using scanning tunneling microscopy (STM), we studied a new molecular system (allyl mercaptan, CH2=CH-CH2-SH) that undergoes chain reaction across the dimer row on the Si(100)-(2 x 1)-H surface at 300 K and produces covalently bonded 1D molecular lines. In combination with the previous findings of chain reaction along the rows, the present observations of self-directed growth of 1D molecular lines across the dimer rows on the Si(100)-(2 x 1)-H surface provide a means to connect any two points (through molecular lines) on a 2D surface.     

The sorption of divalent metal ions on AlPO4

The sorption of Cu(2+), Pb(2+), Ni(2+), and Cd(2+) ions on the aluminum(III) phosphate was observed to increase with increases in the concentration, temperature, and pH of the system. The apparent dissociation (pK(a)), binding (pK(b)) and exchange (pK(ex)) constants of aluminum(III) phosphate were evaluated and found to be dependent upon the temperature and nature of the metal cations. The values of the dissociation constants (pK(a)) followed the order Pb(2+)相似文献   

Biofunctional properties of Eruca sativa Miller (rocket salad) hydroalcoholic extract

Eruca sativa Miller is a worldwide common alimentary plant (rocket leaves). The aim of this study was to correlate the potential in vitro scavenging activity of the E. sativa hydroalcoholic extract (HAE) with its in vivo hypoglycaemic effect. In DDPH free radical (DFR) and ferric-reducing antioxidant power assays, HAE in a concentration dependent manner (25–100 μg/mL) displayed a strong scavenging activity with maximum effect of 88% and 75% at 100 μg/mL, respectively. Daily administration of HAE (50 mg/kg; p.o.) in the in vivo model of alloxan-induced diabetic rabbits for 28 days showed significant reduction in glycaemia, also supported by recovery of body weight. In conclusion, our results give preliminary information on the potential use of this plant as a nutraceutical, useful to control and/or prevent a hyperglycaemic status.     

Phonon spectrum of lead oxychloride Pb<Subscript>3</Subscript>O<Subscript>2</Subscript>Cl<Subscript>2</Subscript>: Ab initio calculation and experiment

IR and Raman spectra of Pb₃O₂Cl₂ in the range of 50–600 cm^–1 have been detected for the first time. Ab initio calculations of the crystal structure and the phonon spectrum of Pb₃O₂Cl₂ in the framework of LCAO approach have been performed by the Hartree–Fock method and in the framework of the density functional theory with the use of hybrid functionals. The results of calculations have made it possible to interpret the experimental vibration spectra and reveal silent modes, which do not manifest themselves in these spectra but influence the optical properties of the crystal.     

Online Capillary Electrophoresis Reaction for Interaction Study of Amino Acid Modified Peptide Nucleic Acid and Proteins

Peptide nucleic acid (PNA) is a nucleic acid analog which consists of purines, pyrimidines bases, and a neutrally charged peptide backbone. The PNA has the potential as a very useful biological probe for protein analysis since it has more in vivo biological stability as compared to DNA- or RNA-based aptamers. Usually, the addition of amino acids or peptide to the PNA backbone is used to improve its water-solubility and cell-permeability, but these modifications may affect the interaction between PNA and proteins. To date, the investigation of the interaction between PNA and proteins is rare, and there is no reported study about the effects of modifications. In this work, we designed two types of amino acid modified PNAs, (Lys)₂-PNA and (Glu)₂-PNA, which kept the same base sequence with 15-mer thrombin aptamer and had two basic lysine and two acidic glutamic acid residues on N-terminal of the peptide backbone, respectively. To rapidly assess the binding affinity and specificity of modified PNA and proteins, the online CE reaction method was developed to analyze the interactions of (Lys)₂-PNA/(Glu)₂-PNA and three proteins: thrombin (THB), single-strand DNA-binding protein (SSB) and human serum albumin (HSA). Meanwhile, the interactions of (Lys)₂-PNA/(Glu)₂-PNA and thrombin were compared with that of the corresponding complementary base sequence (Lys)₂-cPNA/(Glu)₂-cPNA and thrombin. The online CE reaction results showed that the interaction of (Lys)₂-PNA and (Glu)₂-PNA with three proteins was in the order of THB > SSB > HSA. However, (Lys)₂-PNA and (Lys)₂-cPNA showed similar binding affinity with thrombin; while the binding affinity of (Glu)₂-PNA with thrombin was stronger than that of (Glu)₂-cPNA with thrombin. Moreover, the binding constant K_b of (Glu)₂-PNA and three proteins was determined by affinity capillary electrophoresis (ACE). The online CE reaction eliminates the requirement of incubation, and thus it is fast in detection, and easy to operate with minimum cost. The method is particularly suitable for the interaction studies of expensive modified PNAs and proteins, and can assist the design of PNA probe that binds to proteins.     

Loss Behavior of Single-mode Optical Fiber Microbend Sensors

Periodic microbending has been studied to develop an insight into the loss behavior of single-mode microbend sensors by using the finite-difference beam propagation method. Loss sensitivity variations with wavelength are examined, as well as the optical loss dependence on the number of microbends and the modal field perturbations caused by the microbending.     

Second order symmetric duality in multiobjective programming involving cones

An attempt is made to remove certain omissions and inconsistencies in the recent work of Mishra and Lai (European J. Oper. Res., 178:20–26, 2007).     

Bioengineering Functional Copolymers. IX. Poly[(maleic anhydride-co-hexene-1)-g-poly(ethylene oxide)

Amphiphilic bioengineering copolymers having a combination of hydrophilic/hydrophobic linkages and polyelectrolyte behavior, along with an ability to interact with biomacromolecules, in particular with the invertase enzyme, have been synthesized by (a) complex-radical copolymerization of maleic anhydride (MA, the acceptor) and hexene-1 (H-1, the donor) monomers with benzoyl peroxide as the initiator in 1,4-dioxane at 65 degrees C under high-conversion conditions and (b) subsequent grafting (polyesterification) of synthesized poly(MA-alt-H-1) with alpha-methoxy-omega-hydroxy-poly(ethylene oxide) (PEO). Copolymerizations were also carried out in the steady state, in order to essentially reduce the effect of copolymer composition drift. The values of the monomer reactivity ratios (r(1) and r(2)) determined by using the known terminal models of Fineman-Ross (FR) and Kelen-Tüd?s (KT), as well as by nonlinear regression (NLR) analysis, are: r(1) = 0.16 and r(2) = 0.30 (FR), r(1) = 0.14 and r(2) = 0.27 (KT), and r(1) = 0.15 and r(2) = 0.29 (NLR), respectively. All the copolymers and graft copolymers were characterized by FTIR spectroscopy, (1)H{(13)C} NMR spectroscopy, viscometric measurements, and chemical (acid number), thermal (DSC and TGA), and X-ray diffraction analyses. Unlike poly(MA-alt-H-1)s, PEO macrobranched graft copolymers exhibit expressed polyelectrolyte and swelling behavior in diluted and concentrated dioxane solutions, respectively. The copolymer and its PEO hyperbranched derivatives can be used as carriers for enzyme immobilization.