Selective molecular recognition, C-H bond activation, and catalysis in nanoscale reaction vessels

Supramolecular chemistry represents a way to mimic enzyme reactivity by using specially designed container molecules. We have shown that a chiral self-assembled M4L6 supramolecular tetrahedron can encapsulate a variety of cationic guests with varying degrees of stereoselectivity. Reactive iridium guests can be encapsulated, and the C-H bond activation of aldehydes occurs with the host cavity controlling the ability of substrates to interact with the metal center based upon size and shape. In addition, the host container can act as a catalyst by itself. By restricting reaction space and preorganizing the substrates into reactive conformations, it accelerates the sigmatropic rearrangement of enammonium cations.     

Laser transmission through thin cirrus clouds

A near-infrared airborne-laser transmission model for thin cirrus clouds has been developed on the basis of the successive-order-of-scattering approach to account for multiple scattering by randomly and horizontally oriented ice crystals associated with an aircraft-target system. Direct transmission and transmission due to multiple scattering are formulated specifically for this geometric system, in which scattering and absorption associated with aerosols, water vapor, and air are accounted for. A number of sensitivity experiments have been performed for investigation of the effect of aircraft-target position, cirrus cloud optical depth, and ice crystal size on laser transmission for tactical applications. We show that transmission contributions produced by orders of scattering higher than 1 are small and can be neglected. The possibility of horizontal orientation of ice crystals can enhance transmission of laser beams in the aircraft-target geometry. Transmitted energy is strongly dependent on the horizontal distance between the aircraft and the target and on the cloud optical depth as well as on whether the cloud is above or below the aircraft.     

Effect of iron state on crystallization and dissolution in Fe2O3-CaO-SiO2 glasses

The possibility of iron-containing glasses as thermoseeds for hyperthermia of bone tumor was reported previously. There is, however, no report about the effect of iron state on the crystallization of magnetite and the resultant properties. The iron states were determined by Mo¨ssbauer spectroscopy in Fe₂O₃-CaO-SiO₂ system. It was found that the higher CaO content interrupts the crystallization of magnetite crystallites as well as the oxidation of iron, that is, the transformation from Fe³⁺ to Fe²⁺. A sample containing large amounts of Fe²⁺ showed the faster increment of temperature when the alternating magnetic field was applied. In order to use the thermoseed for a hyperthermia, we can say that the composition with low CaO content is most useful.     

A multichannel order-statistic technique for cDNA microarray image processing

This paper introduces an automated image processing procedure capable of processing complementary deoxyribonucleic acid (cDNA) microarray images. Microarray data is contaminated by noise and suffers from broken edges and visual artifacts. Without the utilization of a filter, subsequent tasks such as spot identification and gene expression determination cannot be completed. By employing, in a unique cascade processing cycle, nonlinear filtering solutions based on robust order statistics, the procedure: 1) removes both background and high-frequency corrupting noise and 2) correctly identifies edges and spots in cDNA microarray data. The proposed solution operates directly on the microarray data, does not rely on explicit data normalization or spot separation preprocessing, and operates in a robust manner without using heuristically determined design parameters. Other routine microarray processing operations such as shape manipulations and grid adjustments can be used in conjunction with the developed solution in the processing pipeline. Experimentation reported in this paper indicates that the proposed solution yields excellent performance by removing noise and enhancing spot location determination.     

Structure-based design of inhibitors of the rice blast fungal enzyme trihydroxynaphthalene reductase

Rice Blast Disease, caused by the fungus Pyricularia oryzae, is one of the most important diseases of rice. Several enzymes in the melanin biosynthetic pathway have proven to be valuable targets for development of rice blast fungicides. In particular, inhibitors of trihydroxynaphthalene reductase (3HNR), which catalyzes the conversion of trihydroxynaphthalene to vermelone, have yielded commercially useful rice fungicides. The X-ray structure of 3HNR has been published recently, presenting an opportunity to use this information in the de novo design of novel 3HNR inhibitors that may exhibit useful rice blast activity. We used the LeapFrog program to develop a docking model for interaction of ligands with the active site of THNR. The final model gave a good correlation between calculated binding energy and log Ki and was used to design novel ligands and score compounds for synthesis. Using this as a tool, we synthesized inhibitors in the nanomolar range and also developed several inhibitors that did not conform to the properties of the THNR active site. Leapfrog was able to locate a previously unrecognized binding pocket that could accommodate these otherwise anomalous regions of structure.     

Enzyme kinetic measurements using a droplet-based microfluidic system with a concentration gradient

In this paper, we propose a microfluidic device that is capable of generating a concentration gradient followed by parallel droplet formation within channels with a simple T-junction geometry. Linear concentration gradient profiles can be obtained based on fluid diffusion under laminar flow. Optimized conditions for generating a linear concentration gradient and parallel droplet formation were investigated using fluorescent dye. The concentration gradient profile under diffusive mixing was dominated by the flow rate at sample inlets, while parallel droplet formation was affected by the channel geometry at both the inlet and outlet. The microfluidic device was experimentally characterized using optimal layout and operating conditions selected through a design process. Furthermore, in situ enzyme kinetic measurements of the β-galactosidase-catalyzed hydrolysis of resorufin-β-d-galactopyranoside were performed to demonstrate the application potential of our simple, time-effective, and low sample volume microfluidic device. We expect that, in addition to enzyme kinetics, drug screening and clinical diagnostic tests can be rapidly and accurately performed using this droplet-based microfluidic system.     

Synthesis and characterization of new dithienosilole-based copolymers for polymer solar cells

A series of dithienosilole-based copolymers, poly [(4,4'-bis(2-hexyl)dithieno[3,2-b:2',3'-d]silole)-2,6-diyl-alt-(2,1,3-benzothiadiazole)-5,5'-diyl] (P1), poly[(4,4'-bis(2-hexyl)dithieno[3,2-b:2',3'-d]silole)-2,6-diyl-alt-(2,2'-bithiazole)-5,5'-diyl] (P2), poly[(4,4'-bis(2-hexyl)dithieno[3,2-b:2',3'-d]silole)-2, 6-diyl-alt-(10 -methyl-phenothiazine)-3,7-diyl](P3), poly[(4,4'-bis(2-hexyl)dithieno[3,2-b:2',3'-d]silole)-2,6-diyl-alt-(4,7-bis(2-thienyl)-9,10-anthracene)-5,5'-diyl] (P4) were synthesized by the Pd-catalyzed Stille polymerization method. Electron-deficient benzothiadiazole and bithiazole units and electron-rich phenothiazine and anthracene moieties were incorporated into the polymer backbone to obtain the broad absorption spectrum and to improve the hole-transporting characteristics, respectively. The polymer solar cell (PSC) was fabricated with a layered structure of ITO/PEDOT:PSS/polymer:C71-PCBM (1:3)/LiF/Al. The best performance of PSC was obtained at P3:C71-PCBM which reaches a power conversion efficiency (PCE) of 1.18%, with a short circuit current density (J(sc)) of 4.75 mA/cm2, an open circuit voltage (V(oc)) of 0.71 V, and a fill factor (FF) of 0.35 under AM 1.5G irradiation (100 mW/cm2).