Eisen, Stahl und Ferrolegierungen

Ohne Zusammenfassung     

Light-triggered charge reversal of organic-silica hybrid nanoparticles

A functional nanoparticle with light-triggered charge reversal based on a protected amine-bridged polysilsesquioxane was designed. An emulsion- and amine-free sol-gel synthesis was developed to prepare uniform nanospheres. Photolysis of suspensions of these nanoparticles results in a reversal of the ζ potential. This behavior has been used to trigger nanoparticle self-assembly, nanocomposite hydrogel formation, and nanoparticle release, showing the potential of this material in nanoscale manipulation and nanoparticle therapy.     

Photodeformable spherical hybrid nanoparticles

We report the first synthesis of spherical nanoparticles of a bridged polysilsesquioxane. The hard, brittle nanoparticles are prepared by a simple sol-gel polymerization without surfactants or templates. Particle size ranges from 50 to 100 nm. The organic component of these hybrid nanoparticles is composed of a photolabile coumarin dimer. Irradiation with UV light dissociates the photodimer resulting in rupture of the cross-links and subsequent deformation and eventual "melting" of the nanoparticles.     

Alternating droplet generation and controlled dynamic droplet fusion in microfluidic device for CdS nanoparticle synthesis

A multifunctional and high-efficiency microfluidic device for droplet generation and fusion is presented. Through unique design of the micro-channels, the device is able to alternately generate droplets, generating droplet ratios ranging from 1 ratio 5 to 5 ratio 1, and fuse droplets, enabling precise chemical reactions in several picoliters on a single chip. The controlled fusion is managed by passive control based on the channel geometry and liquid phase flow. The synthesis of CdS nanoparticles utilizing each fused droplet as a microreactor for rapid and efficient mixing of reagents is demonstrated in this paper. Following alternating droplet generation, the channel geometry allows the exclusive fusion of alternate droplets with concomitant rapid mixing and produces supersaturated solution of Cd2+ and S2- ions to form CdS nanoparticles in each fused droplet. The spectroscopic properties of the CdS nanoparticles produced by this method are compared with CdS prepared by bulk mixing.     

Chemically modified dansyl probes: a fluorescent diagnostic for ion and proton detection in solution and in polymers

[reaction: see text] The fluorescence emission intensity of the dansyl group is significantly diminished upon appending an ethyldimethylamino group to the N1 nitrogen substituent. Addition of acids and metal ions (i.e., Zn(2+)) to solutions of trimethylethylenediamine naphthalene sulfonamide (trinsyl) 2 produces a >25-fold increase in fluorescence intensity. Trinsyl probe 2 has been used as a diagnostic for the diffusion of protons and metal ions in a network polymer as well as an optical reporter for the glass transition temperature.     

A synthesis of the welwistatin core

[Structure: see text] An approach to the core structure of the microtubule-targeting agent welwistatin is described. The approach utilizes the type 2 intramolecular Diels-Alder reaction, with indole serving as the tether between diene and dienophile, to form the natural product's characteristic bicyclo[4.3.1]decane skeleton.     

Structural study of adsorption of isonicotinic acid and related molecules on rutile TiO2(1 1 0) I: XAS and STM

X-ray absorption spectroscopy (XAS) and scanning tunneling microscopy (STM) have been used to study the absorption of monolayers of the pyridinecarboxylic acid monomers (isonicotinic acid, nicotinic acid, and picolinic acid) and benzoic acid on a rutile TiO₂(1 1 0) surface. We find that the pyridine and phenyl rings are oriented with their planes largely perpendicular to the surface. The azimuthal orientations are strongly influenced by adsorbate-adsorbate interactions, which in each case leads to at least two different molecular species. In order to reach this conclusion a detailed strategy has been developed for the interpretation of angle-dependent XAS data, which does not rely on any curve fitting procedures.     

The amyloid formation mechanism in human IAPP: dimers have β-strand monomer-monomer interfaces

Early oligomerization of human IAPP (hIAPP) is responsible for β-cell death in the pancreas and is increasingly considered a primary pathological process linked to Type II Diabetes (T2D). Yet, the assembly mechanism remains poorly understood, largely due to the inability of conventional techniques to probe distributions or detailed structures of early oligomeric species. Here, we describe the first experimental data on the isolated and unmodified dimers of human (hIAPP) and nonamyloidogenic rat IAPP (rIAPP). The experiments reveal that the human IAPP dimers are more extended than those formed by rat IAPP and likely descend from extended monomers. Independent all-atom molecular dynamics simulations show that rIAPP forms compact helix and coil rich dimers, whereas hIAPP forms β-strand rich dimers that are generally more extended. Also, the simulations reveal that the monomer-monomer interfaces of the hIAPP dimers are dominated by β-strands and that β-strands can recruit coil or helix structured regions during the dimerization process. Our β-rich interface contrasts with an N-terminal helix-to-helix interface proposed in the literature but is consistent with existing experimental data on the self-interaction pattern of hIAPP, mutation effects, and inhibition effects of the N-methylation in the mutation region.