Biocatalytic enantioselective preparation of phenothiazine-based cyanohydrin acetates: kinetic and dynamic kinetic resolution

Dynamic kinetic resolution is used for the preparation of a series of novel (+)-10-alkyl-phenothiazin-3-ylcyanomethyl acetates. The method exploits a basic resin both for the racemization and formation of phenothiazine-based cyanohydrins and for the decomposition of acetone cyanohydrin in one pot together with Candida antarctica lipase A-catalyzed enantioselective acylation with vinyl acetate in acetonitrile. The Candida antarctica lipase A-catalyzed methanolysis of racemic 10-alkyl-phenothiazin-3-ylcyanomethyl acetates in acetonitrile with E?100 leads to the corresponding (−)-acetates.     

Sensitive miniature single-particle immunoassay of prostate-specific antigen using time-resolved fluorescence

The present study describes the development of a quantitative miniaturized single microparticle immunoassay. The main objective of the study was to evaluate the performance of a miniature heterogeneous immunoassay on a single microparticle in respect to assay kinetics, volume, and sensitivity, binding capacity of microparticles and sensitivity using europium(III) nanoparticle labels. The performance of the single microparticle assay of prostate-specific antigen (PSA) was investigated using different-sized microparticles (60-920 μm in diameter) and microtiter well as a solid-phase. Equilibration time of the assay was shown to be dependent in a linear manner on surface-to-volume ratio, i.e. larger surface-to-volume translated to a faster reaction. However, no correlation between PSA binding capacity and equilibration time was observed in these kinetic studies. Only moderate improvement in assay kinetics was found when PSA binding capacity was increased on a microparticle. Using europium(III) nanoparticle labels, 107 nm in diameter, coated with streptavidin a detection sensitivity of 30 ng l⁻¹ (0.1 amol) was achieved in 1 μl total assay volume per microparticle. This was 50-fold higher compared to the same assay performed with intrinsically fluorescent europium(III) labels.     

Hybrid particles of polystyrene and carboxymethyl cellulose as substrates for copper ions

The synthesis of hybrid particles was carried out by emulsion polymerization of styrene in complexes formed by carboxymethyl cellulose (CMC), a polyanion, and a cationic surfactant, cetyltrimethylammonium bromide (CTAB). CMC chains with variable molecular weights and degrees of substitution were tested. The polymerization condition chosen was that corresponding to CMC chains fully saturated with CTAB and to the onset of pure surfactant micelle formation, namely, at the critical aggregation concentration. The hybrid particles were characterized by zeta potential and light scattering measurements. The period of colloidal stability in the ionic strength of 2.0 mol L(-)(1) NaCl was observed visually. Upon increasing the CMC chain length, the particle characteristics remained practically unchanged, but the colloid stability was increased. The increase in the CMC degree of substitution led to particles with more negative zeta potential values. The adsorption of copper ions (Cu(2+)) on the surface of hybrid particles could be described by the Langmuir model, as determined by potentiometric measurements. The increase in the mean zeta potential values and X-ray absorption near-edge spectra evidenced the immobilization of Cu(2+) ions on the hybrid particles.     

Determination of the glass transition temperature of latex films: Comparison of various methods

The glass transition temperature (T_g) for two latices with different styrene/butadiene compositions was determined by the thermal SPM probe resonance frequency method. The results were compared with the T_g values obtained by differential scanning calorimetry (DSC), dynamical mechanical analysis (DMA), process rheometer (PR) and thermo-mechanical analyzer (TMA) measurements. The T_g values detected by the thermal SPM method agreed well with the T_g values obtained by DSC and calculated by the Fox–Flory equation. DMA, on the other hand, showed a significantly higher T_g value for both latices than those obtained from theoretical calculations, the thermal SPM method and DSC. The T_g obtained from the PR curve was slightly higher for the latex with a low styrene content, whereas good agreement was obtained with the thermal SPM data for the latex with a high styrene content. The glass transition temperature determined by TMA agreed fairly well with the thermal SPM data for the latex with the low styrene content, whilst the value of T_g for the second latex was much less than those obtained by the other methods. The thermal SPM method detects changes in thermal behavior (thermal diffusivity, heat capacity) during heating of the latex films rather than changes in the mechanical properties. Information about the sample history could be seen in the thermal SPM curves, which was further associated with the degree of latex film formation, especially when the roughness of the films was taken into consideration.     

Colloid stability of sodium dihexadecyl phosphate/poly(diallyldimethylammonium chloride) decorated latex

The colloid stability of supramolecular assemblies composed of the synthetic anionic lipid sodium dihexadecyl phosphate (DHP) on cationic poly(diallyldimethylammonium chloride) (PDDA) supported on polystyrene sulfate (PSS) microspheres was evaluated via turbidimetry kinetics, dynamic light scattering for particle sizing, zeta-potential analysis, and determination of DHP adsorption on PDDA-covered particles. At 0.05 g/L PDDA and 5 x 10(9) PSS particles/mL, PDDA did not induce significant particle flocculation and a vast majority of PDDA covered single particles were present in the dispersion so that this was the condition chosen for determining DHP concentration (C) effects on particle size and zeta-potentials. At 0.8 mM DHP, charge neutralization, maximal size, and visible precipitation indicated extensive flocculation and minimal colloid stability for the DHP/PDDA/PSS assembly. At 0.05 g L(-1) PDDA, isotherms of high affinity for DHP adsorption on PDDA-covered particles presented a plateau at a limiting adsorption of 135 x 10(19) DHP molecules adsorbed per square meter PSS which was well above bilayer deposition on a smooth particle surface. The polyelectrolyte layer on hydrophobic particles was swelled and fluffy yielding ca. 6 +/- 1.5 nm hydrodynamic thickness. Maximal and massive adsorption of DHP lipid onto this layer produced polydisperse DHP/PDDA/PSS colloidal particles with low colloid stability and which, at best, remained aggregated as doublets over a range of large lipid concentrations so that it was not possible to evaluate the mean total thickness for the deposited film. The assembly anionic lipid/cationic PDDA layer/polymeric particle was relatively stable as particle doublets only well above charge neutralization of the polyelectrolyte by the anionic lipid, at relatively large lipid concentrations (above 1 mM DHP) with charge neutralization leading to extensive particle aggregation.     

An open-source surface barrier discharge plasma pretreatment for reduced cracking of outdoor wood coatings

The development of a simple surface barrier discharge plasma device is presented to enable more widespread access to and utilization of plasma technology. The application of the plasma device was demonstrated for pretreatment of wood prior to application of protective coatings for outdoor usage. The coatings' overall performance was increased, showing a reduction or absence of cracking due to weathering on plasma-pretreated specimens. Moreover, after ten months of outdoor weathering, the plasma-pretreated specimens showed fewer infections with biotic factors and improved adhesion performance in cross-cut tests, while the surface gloss performed independently from plasma pretreatment. In contrast to that, plasma-pretreated specimens were slightly more prone to discoloration due to outdoor weathering, whereas the plasma pretreatment did not impact the initial color after coating application.

Graphic abstract

     

Rolling Against a Sphere: The Non-transitive Case

We study the control system of a Riemannian manifold M of dimension n rolling on the sphere \(S^n\). The controllability of this system is described in terms of the holonomy of a vector bundle connection which, we prove, is isomorphic to the Riemannian holonomy group of the cone C(M) of M. Using Berger’s list, we reduce the possible holonomies to a few families. In particular, we focus on the cases where the holonomy is the unitary and the symplectic group. In the first case, using the rolling formalism, we construct explicitly a Sasakian structure on M; and in the second case, we construct a 3-Sasakian structure on M.     

Thermal and topographical characterization of polyester- and styrene/acrylate-based composite powders by scanning probe microscopy

The thermal properties of two conventional polyester-based toners and a chemically prepared styrene/acrylate toner with different thermal histories were studied by scanning probe microscopy (SPM) and differential scanning calorimetry (DSC). The thermal transition temperatures detected by SPM agreed with the results of the DSC measurements. The validity of SPM for detecting thermal transitions was further confirmed by studying two amorphous reference polymers with different glass transition points (T_g) and three crystalline reference polymers with different melting points (T_m). When the toner sample was heated by the SPM probe above the glass transition temperature of the toner powder (T_probe > T_g), changes occurred in the surface topography and roughness causing different levels of local sintering of the particles. A set of roughness parameters calculated from the SPM image data were used to quantify the most essential features of toner surfaces. Environmental scanning electron microscopy (ESEM) was used to study the penetration depth of heat dissipated by the SPM probe. The probe-annealing was compared with oven-annealing in order to establish the effect of thermal history on the thermal properties of the materials.     

Syntheses and Crystal Structures of Lanthanide Chloride Complexes with Diglyme

Reactions of [LnCl₃(DME)₂] (Ln = Nd, Sm, Ho, Lu; DME = dimethoxyethane) and diglyme (diglyme = diethylen glycol dimethyl ether) in THF resulted in polymeric [LnCl₃(diglyme)]_n (Ln = Nd ( 1 ), Sm ( 2 )) or mononuclear complexes [LnCl₃(diglyme)(THF)] (Ln = Ho ( 3 ), Lu ( 4 )). Neodymium and samarium atoms in 1 and 2 are eight‐coordinated by three oxygen atoms from diglyme, one terminal and four bridging chloride ions. Holmium and lutetium atoms in 3 and 4 are seven‐coordinated by three oxygen atoms from diglyme, three chloride ions and one oxygen atom from THF. [ErCl₃(diglyme)(H₂O)] ( 5 ) resulted from the reaction of ErCl₃·6H₂O, (CH₃)₃SiCl and diglyme in THF. The molecular structures of 3 , 4 and 5 are similar, with either a molecule of THF coordinated to the lanthanide atom in 3 and 4 or with a molecule of water coordinated in 5 .     

Some aspects of quantitative 2D NMR

We have studied the application of 2D HSQC for quantitative measurements and propose some improvements to the previously published Q-HSQC method. Application of CPMG-INEPT for polarization transfer period suppresses the evolution of J(HH), and thus corrects the shape of the cross-peaks. The better cross-peak shape makes phase correction and integration of the cross-peaks easier. Further, the (13)C resonance offset dependency can have a significant influence to the results. The offset effects can be compensated either by correcting results with a proper coefficient, or using 90 degrees composite (13)C pulses in the pulse sequence. The results show that these modifications improve the applicability of 2D HSQC for quantitative analysis when studying molecules possessing large J(HH) couplings and wide (13)C chemical shift range.