Structure of the inhibitor complex of old yellow enzyme from Trypanosoma cruzi

Old yellow enzyme (OYE) is an NADPH oxidoreductase which contains flavin mononucleotide as prosthetic group. The X-ray structures of OYE from Trypanosoma cruzi (TcOYE) which produces prostaglandin (PG) F(2α) from PGH(2) have been determined in the presence or absence of menadione. The binding motif of menadione, known as one of the inhibitors for TcOYE, should accelerate the structure-based development of novel anti-chagasic drugs that inhibit PGF(2α) production specifically.     

Programmed placement of gold nanoparticles onto a slit-type DNA origami scaffold

A novel DNA scaffold, called a DNA slit, was designed for the programmed positioning of Au nanoparticles (AuNPs), and various patterns of thiolated DNA slits were constructed. AuNPs were correctly placed at the predesigned positions in the thiolated DNA slits, indicating that the thiolated staples and the slit cavities guide the correct assembly of AuNPs.     

Two-dimensional DNA origami assemblies using a four-way connector

Two-dimensional self-assembly of DNA origami structures was carried out using a connector that has connection sites at all four edges. By utilizing this four-way connector, five and eight origami monomers were assembled to form a cruciate and a hollow square structure, respectively.     

Vinyl Polymerization. 282. Vinyl Polymerization Initiated by Dimethylhydroxylamine-Titanous(lll) Chloride Redox System

Abstract

The polymerization of vinyl monomers initiated by dimethylhydroxylamine hydrochloride (DHA)-titanous(III) chloride redox system has been studied in water under a nitrogen atmosphere. In the polymerization of methyl methyacrylate (MMA) initiated by the above system, the rate of polymerization has been found to be proportional to [DHA]^0.5 for DHA concentrations of less than 2.06 × 10^?3 mole/liter, whereas at higher concentrations the rate tends to fall rapidly. The rate has also been found to be proportional to [Ti(m)] ^0.58 and to [MMA] ^1.0. The maximum rate of polymerization has been observed at a 1:1 molar ratio of DHA to Ti(III). The polymerization proceeded via a radical mechanism. The overall activation energy was estimated as 5.5 kcal/mole. It has been suggested that the reduction of dimethylhydroxylamine by titanous(III) chloride yields the dimethylamino radical, which initiates vinyl polymerization. An examination of the initiating capacity of the initiator system for the polymerization of some vinyl monomers has also been made.     

Molecular Recognition by Cyclophane/Guanidinium Supramolecular Receptor Embedded at the Air-Water Interface

In order to develop a supramolecular receptor through a self-assembling process, a site-specific host and an inclusion-type host were mixed as a Langmuir monolayer, and guest binding and pressure-induced fluorescence emission were investigated. A guanidinium amphiphile and several cyclophanes carrying hydrophobic moieties were used as the host molecules; molecular recognition of an aqueous fluorescent guest, 6-p-toluidino-2-naphthalenesulfonic acid (TNS) by binary mixed receptor monolayers was evaluated by a surface pressure-molecular area (π-A) isotherm and a surface fluorescence measurement. An apparent increase in fluorescence intensity was observed when the mixed monolayers of the guanidinium and cyclophane amphiphiles were compressed on an aqueous TNS solution. In contrast, single-component monolayers of the guanidinium or the cyclophane did not show a significant increase in fluorescence emission. In the mixed monolayers, the guest TNS would be bound to the interface by strong electrostatic interaction with the guanidinium, and inclusion of the formed complex probably suppresses the quenching effect in polar medium and/or self-quenching. Experiments with various mixing ratios of these components suggest selective formation of an equimolar cooperative receptor of the guanidinium and the cyclophane. Investigation of the cyclophane structures by fluorescence emission and a competitive binding experiment with another guest were also carried out.     

Insertion of cyclopropanes between a carbonyl carbon and an α-carbon of carbonyl compounds with cyclopropylmagnesium carbenoids

The reaction of the lithium enolates of α-aryl carbonyl compounds with cyclopropylmagnesium carbenoids, derived from 1-chlorocyclopropyl p-tolyl sulfoxides with i-PrMgCl at low temperature, resulted in the formation of β-aryl carbonyl compounds bearing a cyclopropane ring at the α-position with one-carbon homologation in variable yields. The reaction was found to be highly stereospecific with respect to the stereochemistry of the cyclopropylmagnesium carbenoids. Mechanism and origin of the stereospecificity of the reaction are also discussed. This is the first example for the insertion of cyclopropanes in between a carbonyl carbon and an α-carbon of carbonyl compounds.     

High-throughput walkthrough detection portal for counter terrorism: detection of triacetone triperoxide (TATP) vapor by atmospheric-pressure chemical ionization ion trap mass spectrometry

With the aim of improving security, a high‐throughput portal system for detecting triacetone triperoxide (TATP) vapor emitted from passengers and luggage was developed. The portal system consists of a push‐pull air sampler, an atmospheric‐pressure chemical ionization (APCI) ion source, and an explosives detector based on mass spectrometry. To improve the sensitivity of the explosives detector, a novel linear ion trap mass spectrometer with wire electrodes (wire‐LIT) is installed in the portal system. TATP signals were clearly obtained 2 s after the subject under detection passed through the portal system. Preliminary results on sensitivity and throughput show that the portal system is a useful tool for preventing the use of TATP‐based improvised explosive devices by screening persons in places where many people are coming and going. Copyright © 2011 John Wiley & Sons, Ltd.     

Rapid Microwave‐Promoted Synthesis of Polyurethanes from a Fluorene Unit‐Containing Diol and Diisocyanates

A fluorene diol derivative, 9,9‐bis[4‐(2‐hydroxyethoxy)phenyl]fluorene ( 1 ), reacted with diisocyanates such as 1,3‐bis(isocyanatomethyl)cyclohexane ( 2a ), 1,6‐diisocyanatohexane ( 2b ), and 1,3‐bis(isocyanatomethyl)benzene ( 2c ) under temperature‐controlled microwave irradiation to form the corresponding polyurethanes with being 30 000 to 60 000, measured by GPC with reference to polystyrene standards within 5 to 10 min at 160 to 200 °C. In the reactions of 2a and b , the molecular weights were 15 to 20 times higher than those obtained by conventional oil bath heating. For a solvent of the microwave‐promoted reaction, a hydrocarbon compound, decalin, is preferably used to undergo the polymerization cleanly without unfavorable coloration and/or gelation.

     

High-energy diode-pumped picosecond regenerative amplification at 999 nm in wavelength with a cryogenically cooled Yb:LuLiF(4) crystal

A diode-pumped, cryogenically cooled Yb:LuLiF(4) regenerative amplifier has been developed for the first time to our knowledge. A chirped-seed pulse was amplified and compressed in the regenerative amplifier, simultaneously, which generated approximately 6 mJ, 13 ps pulses at 999 nm in wavelength without a pulse compressor. Simultaneous lasing at 999 and 1024 nm, respectively, was demonstrated, which could be used for different frequency generation in the terahertz region.