Simple preparation of a cadmium selenide-montmorillonite hybrid

The immobilization of organically modified cadmium selenide on montmorillonite was investigated by the reaction of modified cadmium selenide nanoparticles with montmorillonite. The intercalation of the nanoparticles was indicated by the expansion of the interlayer space and spectroscopic observations. The diffuse reflectance absorption spectrum of the product showed absorption onset at 567 nm. In comparison to the bulk cadmium selenide, the blue shift of the absorption onset of the hybrid was ascribed to the quantum size effect of the modified cadmium selenide nanoparticles. This study provides a new method for introducing nanoparticles into the interlayer space of layered inorganic materials.     

Photoinduced intramolecular cyclization of o-ethenylaryl isocyanides with organic disulfides mediated by diphenyl ditelluride

Photoinduced reaction of o-ethenylaryl isocyanides with organic disulfides in the presence of diphenyl ditellurides affords the corresponding bisthiolated indole derivatives via a radical cyclization process. The cyclization can proceed at room temperature upon visible-light irradiation and exhibits good tolerance to functional groups. Several organic disulfides also can be employed for this cyclization, and the corresponding bisthiolated indole derivatives are obtained selectively. In addition, the photoinduced reaction of o-ethenylaryl isocyanides with bis(2-aminophenyl) disulfide affords tetracyclic compounds in one portion.     

Dialkyl bisphosphonate platinum(II) complex as a potential drug for metastatic bone tumor

Bisphosphonates have high affinity for hydroxyapatite (HA), which is abundantly present in bone. Also, platinum complexes are known that have a wide spectrum of antitumor activities. The conjugate of bisphosphonate and a platinum complex might have HA affinity and antitumor activity, and become a drug for metastatic bone tumor. In this study, the authors synthesized platinum complexes that had dialkyl bisphosphonic acid as a ligand, and evaluated the possibility of the synthesized complexes as a drug for metastatic bone tumor. The synthesized dialkyl bisphosphonate platinum(II) complex was characterized, and its stability in an aqueous solution was also confirmed. The synthesized platinum complex showed higher HA affinity than other platinum complexes such as cisplatin and carboplatin in an experiment of adsorption to HA. In vitro, the platinum complex showed tumor growth inhibitory effect stronger than or equal to cisplatin, which is the most commonly used antitumor agent. Moreover, the platinum complex showed a bone absorption inhibitory effect on the osteoclast. These results suggest potential of dialkyl bisphosphonate platinum(II) complexes as a drug for metastatic bone tumor.     

Hybrid and biohybrid silicate based materials: molecular vs. block-assembling bottom-up processes

This critical review introduces a discussion on the influence of preparative procedures (nanofabrication) of nanostructured hybrids and biohybrids, comparing their structural and textural characteristics that determine the properties of the resulting materials. Selected examples of silicate-based hybrids of analogous compositions prepared by both molecular and blocks-assembly bottom-up strategies are discussed to show advantages and inconveniences of each methodology (341 references).     

Platinum(II)-based hydrogen-evolving catalysts linked to multipendant viologen acceptors: experimental and DFT indications for bimolecular pathways

Three new [PtCl(2)(bpy)] derivatives tethered to 2, 4, and 6 dicationic viologen moieties, [PtCl(2)(MV2)](4+) (1), [PtCl(2)(MV4)](8+) (2), and [PtCl(2)(MV6)](12+) (3), have been synthesized (MV2(4+)=5-ethoxycarbamoyl-5'-(N-R(1)-carbamoyl)-2,2'-bipyridine, MV4(8+)=5,5'-bis(N-R(1)-carbamoyl)-2,2'-bipyridine, and MV6(12+)=5,5'-bis(N-R(2)-carbamoyl)-2,2'-bipyridine, in which R(1)=Asp(NH-VG)-NH-VG, R(2)=Asp(NH-VG)-Asp(NH-VG)-NH-VG, and VG=-(CH(2))(2)-(+)NC(5)H(4)-C(5)H(4)N(+)-CH(3)). In spite of the higher charge storage capacity of 2 and 3 due to the higher number of acceptor groups (VG groups), compound 1 with the lowest number of VG tethers has turned out to exhibit an outstanding catalytic performance towards the hydrogen evolution from water. Quantitative analysis of UV/Vis-NIR absorption spectral changes during the photolysis for 2 and 3 reveal that approximately 2 electrons per molecule are stored over the acceptor groups during the photolysis, and the storage events saturate after 20 min. As for 1, the total number of electrons stored per molecule increases once during the initial 10 min and then abruptly decreases down to around 0.1 electrons per molecule at 20 min, during which the storage is maximized at 10-20 min with 0.6-0.7 electrons stored per molecule, thereby indicating that the rates of radical formation and consumption are balanced during the photochemical hydrogen evolution reaction. The electrical conductivity measurements reveal that ion-pair adducts (adducts with PF(6)(-) ions in solution) are formed by 2 and 3 but are not given by 1 under the catalysis conditions. These, together with the results of molecular mechanics calculations, reveal that stack of two [PtCl(2)(bpy)] units becomes unfavorable as the number of sterically bulky and highly charged VG units per molecule increases. We have therefore concluded that dimerization that leads to the formation of a Pt-Pt association is a key step in the effective catalytic enhancement with [PtCl(2)(bpy)]-type catalysts.     

6 Mcps photon-counting X-ray computed tomography system using a 25 mm/s-scan linear LSO–MPPC detector and its application to gadolinium imaging

6 Mcps photon counting was carried out using a detector consisting of a 1.0 mm-thick LSO [Lu₂(SiO₄)O] single-crystal scintillator and an MPPC (multipixel photon counter) module in an X-ray computed tomography (CT) system. The maximum count rate was 6 Mcps (mega counts per second) at a tube voltage of 100 kV and a tube current of 0.91 mA. Next, a photon-counting X-ray CT system consists of an X-ray generator, a turntable, a scan stage, a two-stage controller, the LSO–MPPC detector, a counter card (CC), and a personal computer (PC). Tomography is accomplished by repeated linear scans and rotations of an object, and projection curves of the object are obtained by the linear scan with a scan velocity of 25 mm/s. The pulses of the event signal from the module are counted by the CC in conjunction with the PC. The exposure time for obtaining a tomogram was 600 s at a scan step of 0.5 mm and a rotation step of 1.0°, and photon-counting CT was accomplished using gadolinium-based contrast media.     

Synthesis of maresin 1 and (7S)-isomer

Maresin 1 (with the 7R carbon) and (7S)-maresin 1 were synthesized stereoselectively. The conjugated triene system was constructed by Pd-catalyzed coupling of the trans cis-dienylborane (the C10–C22 part) with the trans vinyl iodide corresponding to the C1–C9 part. The stereogenic centers at C7 and C14 were created by Ru-catalyzed asymmetric reduction of ketone and asymmetric epoxidation/kinetic resolution of the racemic alcohol, respectively.     

Silica gel-promoted convenient synthesis of 2-bromo-3-hydroxybenzoate derivatives

A convenient silica gel-promoted synthesis of 2-bromo-3-hydroxybenzoate derivatives has been developed via the Diels–Alder reaction of furans with methyl 3-bromopropiolate, followed by a ring-opening aromatization. In addition, 2-bromo-3-methoxybenzoate, derived from 2-bromo-3-hydroxybenzoate with iodomethane, was found to be a good substrate for Pd-catalyzed cross-coupling reactions, despite its sterically hindered structure.     

Resolving double disulfide bond patterns in SNAP25B using liquid chromatography–ion trap mass spectrometry

Complex disulfide bond patterns in synaptosomal‐associated protein of 25 kD B (SNAP25B) are thought to regulate neurotransmitter release in response to oxidative stress. However, the steric feasibility of each possible disulfide pattern in SNAP25B has not been assessed. To assess the steric feasibility of hypothesized closely spaced complex disulfide patterning in SNAP25B and also the feasibility of identifying complex disulfide bond patterns with MS, we have developed a novel probabilistic analysis to unambiguously resolve complex double disulfide bond patterns by using an ion trap mass spectrometer. We analyzed fragmentation patterns of singly linked peptides to determine likely fragmentation events in an ion trap mass spectrometer and observed double and single backbone cleavage along with heterolytic cleavage of the disulfide bond. We modeled these same events in the doubly disulfide linked SNAP25B peptide and used a cumulative hypergeometric distribution with top–down scoring to both identify and differentiate these bonding patterns. Because of the presence of unique MS/MS peaks, two of the bonding patterns were directly identified. The third was assigned on the basis of full chromatographic separation and confirmed by modeling triple breakage fragments. In total, this work demonstrates the feasibility – and also limitations – of identification of complex intradisulfide patterns by using ion trap‐based collision‐induced dissociation‐based fragmentation methods. Copyright © 2013 John Wiley & Sons, Ltd.