Peptide-mediated nanoengineering of inorganic particle surfaces: a general route toward surface functionalization via peptide adhesion domains

The peptide-mediated functionalization of inorganic particle surfaces is demonstrated on gadolinium oxide (GdO) particles, revealing specific means to functionalize nano- or microparticles. Phage display screening is exploited to select 12mer peptides, which exhibit sequence-specific adhesion onto surfaces of GdO particles. These peptide adhesion domains are exploited to effectively decorate GdO particles with fluorescently labeled poly(ethylene oxide) (PEO), proving to result in a stable surface modification as shown by significant reduction of protein adsorption by 80%, compared to nonfunctionalized particles. Peptide adhesion and stability of the noncovalent coating are investigated by adsorption/elution experiments and Langmuir isotherms. Fluorescence microscopy, contact angle, and energy dispersive X-ray (EDX) measurements confirmed the sequence specificity of the interactions by comparing adhesion sequences with scrambled peptide sequences. Noncovalent, but specific modification of inorganic particle surfaces represents a generic strategy to modulate functionality and function of nano- or microparticle surfaces.     

Speckle photography: mixed domain fractional Fourier motion detection

A reflection-based optical implementation of two simultaneous scale-invariant fractional Fourier transforms (FRTs) is used to develop a novel compact speckle photographic system. The system allows the independent determination of both surface tilting and in-plane translational motion from two sequential mixed domain images captured using a single camera.     

Combination of electrografting and atom-transfer radical polymerization for making the stainless steel surface antibacterial and protein antiadhesive

A two-step "grafting from" method has been successfully carried out, which is based on the electrografting of polyacrylate chains containing an initiator for the atom transfer radical polymerization (ATRP) of 2-(tert-butylamino)ethyl methacrylate (TBAEMA) or copolymerization of TBAEMA with either monomethyl ether of poly(ethylene oxide) methacrylate (PEOMA) or acrylic acid (AA) or styrene. The chemisorption of this type of polymer brushes onto stainless steel surfaces has potential in orthopaedic surgery. These films have been characterized by ATR-FTIR, Raman spectroscopy, atomic force microscopy (AFM), and measurement of contact angles of water. The polymer formed in solution by ATRP and that one detached on purpose from the surface have been analyzed by size exclusion chromathography (SEC) and (1)H NMR spectroscopy. The strong adherence of the films onto stainless steel has been assessed by peeling tests. AFM analysis has shown that addition of hydrophilic comonomers to the grafted chains decreases the surface roughness. According to dynamic quartz crystal microbalance experiments, proteins (e.g., fibrinogen) are more effectively repelled whenever copolymer brushes contain neutral hydrophilic (PEOMA) co-units rather than negatively charged groups (PAA salt). Moreover, a 2- to 3-fold decrease in the fibrinogen adsorption is observed when TBAEMA is copolymerized with either PEOMA or AA rather than homopolymerized or copolymerized with styrene. Compared to the bare stainless steel surface, brushes of polyTBAEMA, poly(TBAEMA-co-PEOMA) and poly(TBAEMA-co-AA) decrease the bacteria adhesion by 3 to 4 orders of magnitude as revealed by Gram-positive bacteria S. aureus adhesion tests.     

Vanadyl C and N-capped tris(phenolate) complexes: influence of pro-catalyst geometry on catalytic activity

Vanadyl complexes of C or N-capped tripodal ligands, possessing distorted tetrahedral geometry at vanadium, serve as extremely active, thermally robust pro-catalysts for ethylene homo- and ethylene/propylene copolymerisation, whereas pseudo-octahedral pro-catalysts produce far lower activities.     

Photophysics of a series of efficient fluorescent pH probes for dual-emission-wavelength measurements in aqueous solutions

This paper evaluates the 5-aryl-2-pyridyloxazole backbone to engineer donor-acceptor fluorescent pH probes after one- or two-photon absorption. Parent fluorophores, as well as derivatives that can be used to label biomolecules, can be easily obtained in good yields. These molecules exhibit a large one-photon absorption in the near-UV range, and a strong fluorescence emission that covers the whole visible domain. The 5-aryl-2-pyridyloxazole derivatives also possess significant cross sections for two-photon absorption. Upon pyridine protonation, large shifts were observed in the absorption spectra after one- and two-photon excitation, as well as in the emission spectra. This feature was used to measure the pK(a) of the investigated compounds that range between 2 and 8. In most of the investigated derivatives, the pK(a) increased upon light excitation and protonation exchanges took place during the lifetime of the excited state, as shown by phase-modulation fluorometry analysis. Several 5-aryl-2-pyridyloxazole derivatives are suggested as efficient probes to reliably measure the pH of aqueous solutions by means of ratiometric methods that are dependent on fluorescence emission.     

Evaluation of capillary ion exchange stationary phase coating distribution and stability using radial capillary column contactless conductivity detection

The use of radial (across) capillary column capacitively coupled contactless conductivity detection is demonstrated as a simple and rapid technique for visualisation of stationary phase longitudinal coverage and coating stability in capillary ion exchange chromatography.     

Simple pyridylmethylamines: efficient and robust N,N-ligands for Suzuki-Miyaura coupling reactions

A series of pyridylmethylamines have been synthesized in one step from commercially available starting material and identified as effective ligands for Pd-catalyzed carbon-carbon bond formation through Suzuki-Miyaura coupling reaction. The N,N-pyridylmethylamine-Pd catalytic systems appeared as an interesting and robust compromise between catalytic efficiency, substrate compatibility, and practical aspects.     

Study of the Effects of Nonlinear Potential Sweeps on Voltammetry

Voltammetric methods use a constant sweep rate during the course of a scan. This paper reports a study of the influence of a nonconstant sweep rate on the voltammetric response. In this approach, either continuously increasing or continuously decreasing potential scan rates can be employed, unlike presently available methods which rely on a constant sweep rate. The voltammetric response of potassium ferrocyanide at a glassy carbon electrode was used as a model system to test the new method. The responses obtained using traditional staircase voltammetry (linear staircase voltammetry) and the new approach (nonlinear staircase voltammetry) were compared by experiment and by simulation. The new approach offers capability for signal enhancement, whereby enhanced current or enhanced peak shape can be obtained by choice of appropriate waveform parameters.     

Rational convexity of non-generic immersed Lagrangian submanifolds

We prove that an immersed Lagrangian submanifold in C ⁿ with quadratic self-tangencies is rationally convex. This generalizes former results for the embedded and the immersed transversal cases.