Manipulation of shell morphology of silicate spheres from structural evolution in a purely inorganic system.

We have investigated the structural transformation of solid silica spheres into various more complex spherical structures including flower-like, thick or thin nanosheet-shelled and porous shelled spheres. In the absence of organic additives, sodium salts contained in this inorganic reaction system apparently direct the silica dissolution and regrowth of dissolved silicate at the nanometer-scale, leading to the formation of a nanosheet network rather than solid aggregates. Subsequent removal of the salts by simple water washing results in voids in the siloxane network and a significant availability of surface silanol groups so that the resulting nanosheets and spheres composed of them possess large surface areas, pore volumes, and morphological flexibility, which can be varied by an applied stimulus.

Arylpyrrole oligomers as tunable anion receptors.

A novel type of arylpyrrole oligomer possessing an appropriate electropositive cavity has been designed, prepared and analysed for use as readily accessible receptors for negatively charged guests. Affinities of the receptors for various anions were determined by UV/Vis titration experiments and in depth insights into the host-guest interactions were gained by performing (1)H NMR titration experiments and X-ray crystallographic structure analyses. Experimentally determined association constants were correlated with the calculated maximum electrostatic potentials of the electropositive cavities of the receptors, allowing estimation of the strengths of host-guest associations in similar compounds.

Simultaneous electropolymerization and electro-click functionalization for highly versatile surface platforms.

Simple preparation methods of chemically versatile and highly functionalizable surfaces remain rare and present a challenging research objective. Here, we demonstrate a simultaneous electropolymerization and electro-click functionalization process (SEEC) for one-pot self-construction of aniline- and naphthalene-based functional polymer films where both polymerization and click functionalization are triggered by applying electrochemical stimuli. Cyclic voltammetry (CV) can be applied for the simultaneous oxidation of 4-azidoaniline and the reduction of Cu(II) ions, resulting in polymerization of the former, and the Cu(I)-catalyzed alkyne/azide cycloaddition ("click" chemistry).

Bioactive flake-shell capsules: soft silica nanoparticles for efficient enzyme immobilization.

Amorphous silica particles are used extensively in industrial processes as well as in scientific and biomedical research. Flake-shell silica nanoparticles, prepared by self-templating hydrothermal synthesis, exhibit large surface areas and pore volumes, hollow spherical morphology, as well as hydrophilic surfaces, affording great potential for their application in enzyme immobilization. In this work we show that the shell, which is composed of a network of silica flakes, promotes uptake of enzymes of different sizes, i.

Time-resolved single molecule fluorescence spectroscopy of an α-chymotrypsin catalyzed reaction.

Single molecule fluorescence spectroscopy offers great potential for studying enzyme kinetics. A number of fluorescence reporter systems allow for monitoring the sequence of individual reaction events with a confocal microscope. When using a time-correlated single photon counting (TCSPC) detection scheme, additional information about the fluorescence lifetimes of the fluorophores can be obtained.

Dynamic disorder in single-enzyme experiments: facts and artifacts.

Using a single-molecule fluorescence approach, the time series of catalytic events of an enzymatic reaction can be monitored, yielding a sequence of fluorescent "on"- and "off"-states. An accurate on/off-assignment is complicated by the intrinsic and extrinsic noise in every single-molecule fluorescence experiment. Using simulated data, the performance of the most widely employed binning and thresholding approach was systematically compared to change point analysis.

Morpholinecarbonyl-Rhodamine 110 based substrates for the determination of protease activity with accurate kinetic parameters.

Commonly used fluorogenic substrate analogues for the detection of protease activity contain two enzyme-cleavable bonds conjugated to the fluorophore. Enzymatic cleavage follows a two-step reaction with a monoamide intermediate. This intermediate shows fluorescence at the same wavelength as the final product complicating the kinetic analysis of fluorescence-based assays.