One-pot synthesis of amphiphilic superparamagnetic FePt nanoparticles and magnetic resonance imaging in vitro

Monodispersed amphiphilic FePt nanoparticles with the diameter of about 4 nm were synthesized by high temperature pyrolysis of iron(III) acetylacetonate and platinum(II) acetylacetonate. Their amphiphilicity is contributed to the tetraethylene glycol (TEG) and oleic acid (OA) on the surface, which is confirmed by FTIR and XPS spectra. They provide a superparamagnetic property with the saturation magnetization (Ms) of about 25 emu/g and the transverse relaxivity (r₂) of about 122.6 mM⁻¹ s⁻¹ in aqueous solutions. Furthermore, FePt nanoparticles show low cytotoxicity in living cells. They can be uptaken by HeLa cells effectively and result in the obvious decrease of T₂ relaxation time after internalization.     

Periodic solutions for generalized Liénard neutral equation with variable parameter

By means of Mawhin’s continuation theorem, existence criteria is established for the periodic solutions to a neutral equation with variable parameter. It is worth stating that the coefficient c$c$ is not a constant, which is different from the corresponding ones of past work.     

Attomole microarray detection of microRNAs by nanoparticle-amplified SPR imaging measurements of surface polyadenylation reactions

Multiple microRNAs (miRNAs) are detected in a microarray format using a novel approach that combines a surface enzyme reaction with nanoparticle-amplified SPR imaging (SPRI). The surface reaction of poly(A) polymerase creates poly(A) tails on miRNAs hybridized onto locked nucleic acid (LNA) microarrays. DNA-modified nanoparticles are then adsorbed onto the poly(A) tails and detected with SPRI. This ultrasensitive nanoparticle-amplified SPRI methodology can be used for miRNA profiling at attomole levels.     

Local discontinuous Galerkin methods with explicit-implicit-null time discretizations for solving nonlinear diffusion problems

In this paper,we discuss the local discontinuous Galerkin methods coupled with two specific explicitimplicit-null time discretizations for solving one-dimensional nonlinear diffusion problems Ut=(a(U)Ux)x.The basic idea is to add and subtract two equal terms a0 Uxx the right-hand side of the partial differential equation,then to treat the term a0 Uxx implicitly and the other terms(a(U)Ux)x-a0 Uxx explicitly.We give stability analysis for the method on a simplified model by the aid of energy analysis,which gives a guidance for the choice of a0,i.e.,a0≥max{a(u)}/2 to ensure the unconditional stability of the first order and second order schemes.The optimal error estimate is also derived for the simplified model,and numerical experiments are given to demonstrate the stability,accuracy and performance of the schemes for nonlinear diffusion equations.     

Copper, a chemical Janus: two copper(II) complexes with different ligand in one single crystal

A chemical Janus, binuclear copper(II) complexes, {[Cu(TPA)Cl][Cu(BPA)Cl]}(ClO₄)₂ (TPA = Tris(2-pyridylmethyl) amine, BPA = bis-(2-pyridylmethyl)amine) containing two different ligands has been synthesized and characterized by X-ray single crystal analysis. Crystal data: triclinic, space group P1$sm, a = 12.529(3), b = 12.655(3), c = 13.458(3) Å, = 70.48(3), = 67.40(3), = 75.81(3)°, D _x = 1.648 mg m^–3, and Z = 2. The molecular structure shows that the binuclear copper complex consists of two positive cation and two perchlorate anions. The positive cations moieties have different ligands. Cu(1) is coordinated by four nitrogen atoms from TPA and one chloride atom, forming a square-pyramidal geometry, whereas the coordinate number of Cu(2) is four, three of which are from BPA, one from chloride. There are two weak bonds between the Cl(2a) ion and the Cu(2) ion (2.844 Å) and the distance of Cu(2)=O(13) is 2.750(9) Å.     

Synthesis and Crystal Structure of Cu( Ⅱ ) Adduct with N-(4-Chlorophenyl)aza 15-Crown-5

The title compound C18 H25 NC4ClBr2Cu crystallizes in space group P 1 with a = 1.0105(2)nm b=1.0821(1) nm, c=1. 1007(2) nm, a=80. 00(1)°,β=80. 26(1)° γ=77. 83(1)°. Z=2, D = 1. 831 g/cm3, μ=62. 658 cm-1(Mok(?)). The final refinement converged to R=0. 031 for 2547 independent observed reflections. The complex molecule consists of two cationic moieties (HL)+ and an anion which appears as a bromide-bridged copper dimer (Cu2Br6)2-. This structural characterization seems to be rare in metal complexes with crown-ether.     

Paramagnetic and diamagnetic binuclear copper(II) complexes with different bidentate exogenous bridges: synthesis, spectroscopy and magnetic properties

Summary Four binuclear Cu^II complexes, [Cu₂(L)(-X)], have been prepared and characterized, where H₃L is a 2:1 Schiff base derived from 2-hydroxy-1-naphthaldehyde and 1,3-diamino-2-propanol and X = 1,3-N₃ (1), C₃H₃N₂ (pyrazolate) (2), AcO (3) and PhCO₂ (4). The Cu^IIions are bridged by endogenous alkoxide and bidentate exogenous bridges. The variable-temperature magnetic analyses show that complexes (2)–(4) exhibit antiferro-magnetic coupling with the exchange integrals, 2J, from- 188 to -158 cm^-1. The -1,3-azide-bridged binuclear Cu^II complex (1) shows the essential features of diamagnetism through measurements of its variable-temperature susceptibility and e.p.r. spectra. The results suggest that (1) can act as a diamagnetic model for metazidohemocyanin.     

Adsorption of fibrinogen and lysozyme on silicon grafted with poly(2-methacryloyloxyethyl phosphorylcholine) via surface-initiated atom transfer radical polymerization

Surfaces based on grafted poly(2-methacryloyloxyethyl phosphorylcholine) (poly(MPC)) "brushes" with a constant graft density of 0.39 chain/nm2 and chain length from 5 to 200 monomer units were prepared by surface-initiated atom transfer radical polymerization (ATRP) on silicon wafers. The chain length and layer thickness of the poly(MPC) grafts were varied via the ratio of MPC to sacrificial initiator. The surfaces were characterized by water contact angle, XPS, and AFM. The effect of poly(MPC) chain length on fibrinogen and lysozyme adsorption was studied in TBS buffer at pH 7.4. The adsorption of both proteins on the poly(MPC)-grafted surfaces was greatly reduced compared to the unmodified silicon. Adsorption decreased with increasing chain length of the poly(MPC) grafts. Grafts of chain length 200 (MW 59 000) gave adsorption levels of 7 and 2 ng/cm2, respectively, for fibrinogen and lysozyme at 1 mg/mL protein concentration, corresponding to reductions of greater than 98% compared to the unmodified silicon. Adsorption experiments using mixtures of the two proteins showed that the suppression of protein adsorption on the poly(MPC)-grafted surfaces was not strongly dependent on protein size or charge.     

Emulsion atom transfer radical block copolymerization of 2‐ethylhexyl methacrylate and methyl methacrylate

The emulsion atom transfer radical block copolymerization of 2‐ethylhexyl methacrylate (EHMA) and methyl methacrylate (MMA) was carried out with the bifunctional initiator 1,4‐butylene glycol di(2‐bromoisobutyrate). The system was mediated by copper bromide/4,4′‐dinonyl‐2,2′‐bipyridyl and stabilized by polyoxyethylene sorbitan monooleate. The effects of the initiator concentration and temperature profile on the polymerization kinetics and latex stability were systematically examined. Both EHMA homopolymerization and successive copolymerization with MMA proceeded in a living manner and gave good control over the polymer molecular weights. The polymer molecular weights increased linearly with the monomer conversion with polydispersities lower than 1.2. A low‐temperature prepolymerization step was found to be helpful in stabilizing the latex systems, whereas further polymerization at an elevated temperature ensured high conversion rates. The EHMA polymers were effective as macroinitiators for initiating the block polymerization of MMA. Triblock poly(methyl methacrylate–2‐ethylhexyl methacrylate–methyl methacrylate) samples with various block lengths were synthesized. The MMA and EHMA reactivity ratios determined by a nonlinear least‐square method were ～0.903 and ～0.930, respectively, at 70 °C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1914–1925, 2006