A glass capillary microelectrode based on capillarity and its application to the detection of L-glutamate release from mouse brain slices.

A new glass capillary microelectrode for L-glutamate is described using pulled glass capillaries (tip size, approximately 12.5 microm) with a very small volume (approximately 2 microl) of inner solution containing glutamate oxidase (GluOx) and ascorbate oxidase. The operation of the electrode is based on capillary action that samples L-glutamate into the inner solution. The enzyme reaction by GluOx generates hydrogen peroxide that is detected at an Os-gel-HRP polymer modified Pt electrode in a three-electrode configuration. The amperometric response behavior of the electrode was characterized in terms of the capillarity, response time, sensitivity and selectivity for measurements of L-glutamate. The currents at 0 V vs. Ag/AgCl increased linearly with the L-glutamate concentration from 10 to 150 microM for in vitro and in situ calibrations. The response was highly selective to L-glutamate over ascorbate, dopamine, serotonin and other amino acids. The detection of L-glutamate in the extracellular fluids of different regions of mouse hippocampal slices under stimulation of KCl was demonstrated.     

Efficient two-step conversion of alpha,beta-unsaturated aldehydes to optically active gamma-oxy-alpha,beta-unsaturated nitriles and its application to the total synthesis of (+)-patulolide C

[reaction: see text] An efficient two-step conversion of alpha,beta-unsaturated aldehydes into optically active gamma-oxy-alpha,beta-unsaturated nitriles is described. First, catalytic asymmetric cyanation-ethoxycarbonylation using (S)-YLi(3)tris(binaphthoxide) (YLB) afforded chiral allylic cyanohydrin carbonate. Second, a [3,3]-sigmatropic rearrangement proceeded without racemization under thermal conditions to give gamma-oxy-alpha,beta-unsaturated nitriles. Lewis acids were also effective for the rearrangement, and the reaction proceeded smoothly under mild conditions. To demonstrate the utility of the conversion, concise catalytic enantioselective total synthesis of (+)-patulolide C was performed.     

Mixed La-Li heterobimetallic complexes for tertiary nitroaldol resolution

A kinetic resolution of tertiary nitroaldols derived from simple ketones is described. Mixed BINOL/biphenol La-Li heterobimetallic complexes gave the best selectivity in retro-nitroaldol reactions of racemic tertiary nitroaldols. By using a mixture of La-Li3-(1a)3 complex (LLB 2a) and La-Li3-(1b)3 (LLB* 2b) complex in a ratio of 2/1, chiral tertiary nitroaldols were obtained in 80-97% ee and 30-47% recovery yield.     

Laser ion-acceleration scaling laws seen in multiparametric particle-in-cell simulations

The ion acceleration driven by a laser pulse at intensity I= 10(20)-10(22) W/cm(2) x (microm/lambda)(2) from a double layer target is investigated with multiparametric particle-in-cell simulations. For targets with a wide range of thickness l and density n(e), at a given intensity, the highest ion energy gain occurs at certain electron areal density of the target sigma = n(e)l, which is proportional to the square root of intensity. In the case of thin targets and optimal laser pulse duration, the ion maximum energy scales as the square root of the laser pulse power. When the radiation pressure of the laser field becomes dominant, the ion maximum energy becomes proportional to the laser pulse energy.     

Electron, positron, and photon wakefield acceleration: trapping, wake overtaking, and ponderomotive acceleration

The electron, positron, and photon acceleration in the first cycle of a laser-driven wakefield is investigated. Separatrices between different types of the particle motion (trapped, reflected by the wakefield and ponderomotive potential, and transient) are demonstrated. The ponderomotive acceleration of electrons can be largely compensated by the wakefield action, in contrast to positrons and positively charged mesons. The electron bunch energy spectrum is analyzed. The maximum upshift of an electromagnetic wave frequency during reflection from the wakefield is obtained.     

Study on temperature response in raspberry-form gels of poly (N,N-diethylacrylamide)

Slow swelling and shrinking rates are a significant challenge for some applications of temperature-sensitive hydrogels. This study reports raspberry-form poly N,N-diethylacrylamide (DEAA) gel particles, which are aggregates of single spherical gel particles. The raspberry-form gel particles show improved temperature-response rates especially for swelling. This improvement in the response rate is attributed to two key factors: the free space between the individual gel particles that make up the aggregated gel particle, and the constraints from the contact points between the individual gel particles. During the swelling process, the polymer chain networks can diffuse at the faster rate characteristic of the individual gel particles constructing the raspberry-form gel, and consequently the response rate of the overall raspberry-form gels can be accelerated. During the shrinking process, the constraints from the contact points between the individual gels dominate the polymer chain diffusion and the shrinking rate because of non-zero shear modulus. The shrinking behavior was affected not by the individual particle size, but rather the apparent gel size and shape.