Bioinspired Chemical Communication between Synthetic Nanomotors

While chemical communication plays a key role in diverse natural processes, the intelligent chemical communication between synthetic nanomotors remains unexplored. The design and operation of bioinspired synthetic nanomotors is presented. Chemical communication between nanomotors is possible and has an influence on propulsion behavior. A chemical “message” is sent from a moving activator motor to a nearby activated (receiver) motor by release of Ag⁺ ions from a Janus polystyrene/Ni/Au/Ag activator motor to the activated Janus SiO₂/Pt nanomotor. The transmitted silver signal is translated rapidly into a dramatic speed change associated with the enhanced catalytic activity of activated motors. Selective and successive activation of multiple nanomotors is achieved by sequential localized chemical communications. The concept of establishing chemical communication between different synthetic nanomotors paves the way to intelligent nanoscale robotic systems that are capable of cooperating with each other.     

A Click Cage: Organelle‐Specific Uncaging of Lipid Messengers

Lipid messengers exert their function on short time scales at distinct subcellular locations, yet most experimental approaches for perturbing their levels trigger cell‐wide concentration changes. Herein, we report on a coumarin‐based photocaging group that can be modified with organelle‐targeting moieties by click chemistry and thus enables photorelease of lipid messengers in distinct organelles. We show that caged arachidonic acid and sphingosine derivatives can be selectively delivered to mitochondria, the ER, lysosomes, and the plasma membrane. By comparing the cellular calcium transients induced by localized uncaging of arachidonic acid and sphingosine, we show that the precise intracellular localization of the released second messenger is crucial for the signaling outcome. Ultimately, we anticipate that this new class of caged compounds will greatly facilitate the study of cellular processes on the organelle level.     

Lipase catalyzed copolymerization of 3(S)-isopropylmorpholine-2,5-dione and D,L-lactide

The polymerization and copolymerization of 3(S)-isopropylmorpholine-2,5-dione (IPMD) and D,L-lactide (DLLA) were carried out in the presence of Porcine pancreatic lipase type II (PPL) as a catalyst at 100 degrees C for 168 h. Homopolymers and random copolymers of various compositions were obtained with a carboxylic acid group at one end and a hydroxyl group at the other end. The glass transition temperature of the copolymers decreases with increasing mole fraction of DLLA residue in the copolymers.     

Silver incorporation into cathodes for solid oxide fuel cells operating at intermediate temperature

Silver (Ag) at 0.1–2.0 wt% was incorporated into cathodes for solid oxide fuel cells as a catalyst for oxygen reduction. A novel processing route for Ag incorporation ensuring a very homogeneous Ag ion distribution is presented. From the results of X-ray powder diffraction it can be concluded that the La_0.65Sr_0.3MnO_3– perovskite phase is already formed at 900 °C. The solubility of Ag in the crystal lattice in this type of perovskite was below 1 wt%. The electrochemical tests of these materials show that there is only a slight catalytic effect of Ag. Scanning electron microscopy reveals a low mechanical contact of the cathode grains to the electrolyte due to the low cathode sintering temperature that was chosen.     

Kinetics and mechanisms of gas phase elimination of ethyl 1‐piperidine carboxylate,ethyl pipecolinate,and (revisited) ethyl 1‐methyl pipecolinate

The kinetics of the gas‐phase elimination of the title compounds has been determined in a static reaction system over the temperature range of 340–420°C and pressure range of 45–96 Torr. The reactions proved to be homogeneous, unimolecular, and obey a first‐order rate law. The estimated rate coefficients are represented by the following Arrhenius expressions: Ethyl 1‐piperidine carboxylate Ethyl pipecolinate Ethyl 1‐methyl pipecolinate The first step of decomposition of these esters is the formation of the corresponding carboxylic acids and ethylene. The acid intermediate undergoes a very fast decarboxylation process. The mechanism of this elimination reactions is suggested on the basis of the kinetic and thermodynamic parameters. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 383–389, 2005     

Reactivity of functional groups on the protein surface: development of epoxide probes for protein labeling

We present the development of new affinity probes for protein labeling based on an epoxide reactive group. Systematic screening revealed that an epoxide functionality possesses the special combination of stability and reactivity which renders it stable toward proteins in solution but reactive on the protein surface outside the active site (proximity-induced reactivity). Highly efficient and selective labeling of purified HCA II (human carbonic anhydrase II) was achieved. For instance, 2 equiv of epoxide probe 9 was sufficient for nearly quantitative labeling of HCA II (>90% yield, 20 h reaction time). MS analysis of the labeled protein revealed that 1 equiv of the probe was attached and that labeling occurred at a single residue (His 64) outside the active site. Importantly, epoxide probe 9 selectively labeled HCA II both in simple protein mixtures and in cellular extracts. In addition to the chemical insight and its relevance to many epoxide-containing natural products, this study generated a promising lead in the development of new affinity probes for protein labeling.     

From metal to ligand electroactivity in nickel(II) oxamato complexes

The locus of oxidation in square-planar nickel(ii) oxamato complexes can be continuously shifted from the metal to the ligand by an appropriate choice of electron-donating substituents on the aromatic moiety of the ligand.