Simple methods for tuning the pore diameter of mesoporous carbon

The organic-organic self-assembly method with Resorcinol (R)/Formaldehyde (F) and Pluronic F127 has been employed to synthesize mesoporous carbon (MC). The pore diameter of the MC has been tuned from 7 to 12.5 nm by changing the molar ratio of carbon sources to surfactant and polymerization time.     

Syntheses and properties of triborane(5)s possessing bulky diamino substituents on terminal boron atoms

The present communication reports the chemistry of three linear triborane(5) compounds possessing bulky diamino substituents on the terminal boron atoms. Fluorotriborane 2 was synthesized by a reaction of boryllithium and BF(3)·OEt(2). Halogen exchange reaction of 2 took place by a treatment with ClSiMe(3) to give the corresponding chlorotriborane(5) 3. Addition of silver tetraarylborate to 3 in ether afforded a hydroxylated triborane(5) compound 5 probably via an unstable cationic boron intermediate 4.     

Investigation of aromaticity and photophysical properties in [18]/[20]π porphycene derivatives

In this study, we have investigated the relationship between aromaticity and photophysical properties of trifluoromethyl-substituted [18]/[20]π porphycenes by using theoretical calculations and various spectroscopic methodologies. Interestingly, we have found that the HOMO-LUMO gap of [20]π porphycene is larger than that of [18]π porphycene, which is in a sharp contrast with those of typical [4n]/[4n+2]π porphyrinoids. Based on our observations, we demonstrate that the origin of this contrasting feature of [20]π porphycene arises from the uniquely large energy splitting between LUMO and LUMO+1 of [18]π porphycene compared with other aromatic [4n+2]π porphyrinoids with nearly degenerate LUMO/LUMO+1. Consequently, we can propose that the energy difference between LUMO and LUMO+1 levels of aromatic [4n+2]π porphyrinoids is an important factor in determining the electronic nature of their corresponding antiaromatic [4n]π porphyrinoids. Moreover, to the best of our knowledge, this is the first study to illustrate the photophysical properties of porphycenes with [4n]π electronic circuits.     

Transglutaminase-mediated synthesis of a DNA-(enzyme)n probe for highly sensitive DNA detection

A new synthetic strategy for DNA-enzyme conjugates with a novel architecture was explored using a natural cross-linking catalyst, microbial transglutaminase (MTG). A glutamine-donor substrate peptide of MTG was introduced at the 5-position on the pyrimidine of deoxyuridine triphosphate to prepare a DNA strand with multiple glutamine-donor sites by polymerase chain reaction (PCR). A substrate peptide that contained an MTG-reactive lysine residue was fused to the N terminus of a thermostable alkaline phoshatase from Pyrococcus furiosus (PfuAP) by genetic engineering. By combining enzymatically the substrate moieties of MTG introduced to the DNA template and the recombinant enzyme, a DNA-(enzyme)(n) conjugate with 1:n stoichiometry was successfully obtained. The enzyme/DNA ratio of the conjugate increased as the benzyloxycarbonyl-L-glutaminylglycine (Z-QG) moiety increased in the DNA template. The potential utility of the new conjugate decorated with signaling enzymes was validated in a dot blot hybridization assay. The DNA-(enzyme)(n) probe could clearly detect 10(4) copies of the target nucleic acid with the complementary sequence under harsh hybridization conditions, thereby enabling a simple detection procedure without cumbersome bound/free processes associated with a conventional hapten-antibody reaction-based DNA-detection system.     

Span 80 vesicles have a more fluid, flexible and "wet" surface than phospholipid liposomes

The surface properties of Span 80 vesicles at various cholesterol contents, together with those of various liposomes, were characterized by using fluorescence probes. The membrane fluidity of the Span 80 vesicles was measured by 1,6-diphenyl-1.3.5-hexatriene (DPH) and trimethlyammonium-DPH (TMA-DPH), and the results suggested that the surface of the Span 80 vesicles was fluid due to the lateral diffusion of Span 80 molecules. The depolarization measured by TMA-DPH and the headgroup mobility measured by dielectric dispersion analysis indicated the high mobility of the head group of Span 80 vesicles. This suggested that the surface of Span 80 vesicles was flexible due to the head group structure of Span 80, sorbitol. In addition, spectrophotometric analysis with 6-dodecanoyl-N, N-dimethyl-2-naphthylamine and 8-anilino-1-naphthalenesulfonic acid indicated that the water molecules could easily invade into the interior of the Span 80 vesicle membrane, suggesting that the membrane surface was more wet than the liposome surface. These surface properties indicated that the protein could interact with the interior of vesicle membranes, which was similar to the case of cholesterol. Thus the present results confirmed that the Span 80 vesicle surfaces showed the unique characteristics of fluidity, flexibility, and "wetness", whereas the liposome surfaces did not.     

Fabrication of Transparent,Tough, and Conductive Shape‐Memory Polyurethane Films by Incorporating a Small Amount of High‐Quality Graphene

We report a mechanically strong, electrically and thermally conductive, and optically transparent shape‐memory polyurethane composite which was fabricated by introducing a small amount (0.1 wt%) of high‐quality graphene as a filler. Geometrically large (≈4.6 μm²), but highly crystallized few‐layer graphenes, verified by Raman spectroscopy and transmission electron microscopy, were prepared by the sonication of expandable graphite in an organic solvent. Oxygen‐ containing functional groups at the edge plane of graphene were crucial for an effective stress transfer from the graphene to polyurethane. Homogeneously dispersed few‐layered graphene enabled polyurethane to have a high shape recovery force of 1.8 MPa cm⁻³. Graphene, which is intrinsically stretchable up to 10%, will enable high‐performance composites to be fabricated at relatively low cost and we thus envisage that such composites may replace carbon nanotubes for various applications in the near future.     

Rapid determination of nitroimidazole residues in honey by liquid chromatography/tandem mass spectrometry

We developed a rapid and efficient means of determining residues of four nitroimidazoles-i.e., dimetridazole, ipronidazole, metronidazole, and ronidazole-and three hydrophilic metabolites- i.e., 2-hydroxymethyl-1-methyl-5-nitroimidazole, 1 -methyl-2-(2'-hydroxyisopropyl)-5-nitroimidazole, and 1-(2-hydroxyethyl)-2-hydroxymethyl-nitroimidazole--in honey. We applied a QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) procedure improved to suit a nitroimidazole analysis, which is fast (approximately 30 min) and uses less organic solvent. The procedure involves initial single-phase extraction of 5 g of honey with acetonitrile containing 1% acetic acid, followed by liquid-liquid partitioning involving the addition of 5 g sodium chloride, 1.5 g trisodium citrate dihydrate, and 4 g magnesium sulfate. Moreover, matrix from honey was reduced by an SPE method with an alumina-N cartridge. The samples were analyzed using LC/MS/MS. Chromatographic separation of these nitroimidazoles and metabolites was performed in the gradient mode on a pentafluorophenylpropyl-bonded silica column (150x2.0 mm, 3 pm particle size) at 40 degrees C. The mobile phase consisted of a 0.01% acetic acid solution and acetonitrile, and the flow rate was 0.2 mL/min. The method was validated using honey spiked with these nitroimidazoles from 0.1 to 0.5 microg/kg. The overall recovery of the seven nitroimidazoles ranged from 76.1 to 98.5%; intra- and interassay CV values were <9.5 and <14.2%, respectively. The LOQ ranged from 0.1 to 0.5 microg/kg. LC/MS/MS coupled with the QuEChERS method showed good potential as a method for determining nitroimidazole residues in honey.     

Formation and Stability of Binary Complexes of Divalent Ecotoxic Ions (Ni, Cu, Zn, Cd, Pb) with Biodegradable Aminopolycarboxylate Chelants (dl-2-(2-Carboxymethyl)Nitrilotriacetic Acid, GLDA, and 3-Hydroxy-2,2′-Iminodisuccinic Acid, HIDS) in Aqueous Solutions

The protonation and complex formation equilibria of two biodegradable aminopolycarboxylate chelants {dl-2-(2-carboxymethyl)nitrilotriacetic acid (GLDA) and 3-hydroxy-2,2??-iminodisuccinic acid (HIDS)} with Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺ and Pb²⁺ ions were investigated using the potentiometric method at a constant ionic strength of I?=?0.10?mol·dm^?3 (KCl) in aqueous solutions at 25?±?0.1?°C. The stability constants of the proton?Cchelant and metal?Cchelant species for each metal ion were determined, and the concentration distributions of various complex species in solution were evaluated for each ion. The stability constants (log₁₀ K _ML) of the complexes containing Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺ and Pb²⁺ ions followed the identical order of log₁₀ K _CuL?>?log₁₀ K _NiL?>?log₁₀ K _PbL?>?log₁₀ K _ZnL?>?log₁₀ K _CdL for either GLDA (13.03?>?12.74?>?11.60?>?11.52?>?10.31) or HIDS (12.63?>?11.30?>?10.21?>?9.76?>?7.58). In each case, the constants obtained for metal?CGLDA complexes were larger than the corresponding constants for metal?CHIDS complexes. The conditional stability constants (log₁₀ $ K_{\text{ML}}^{'} $ ) of the metal?Cchelant complexes containing GLDA and HIDS were calculated in terms of pH, and compared with the stability constants for EDTA and other biodegradable chelants.     

Palladium-catalyzed asymmetric synthesis of 2-pyrrolidinones with a quaternary carbon stereocenter

A palladium-catalyzed asymmetric synthesis of 2-pyrrolidinones with a quaternary stereocenter at the 3-position has been achieved by the reaction of γ-methylidene-δ-valerolactones with alkyl isocyanates. High enantioselectivity has been realized by employing a newly synthesized chiral phosphoramidite ligand.     

Synthesis of novel IP agonists via N-aminoethyl cyclic amines prepared by decarboxylative ring-opening reactions

An efficient synthesis of a highly potent and selective IP (PGI(2) receptor) agonist that is not structurally analogous to PGI(2) is described. This synthesis is accomplished through the following key steps: Nucleophilic ring-opening of 3-(4-chlorophenyl)-oxazolidin-2-one prepared by a one-pot procedure with 4-piperidinol and selective O-alkylation of 1-(2-(4-chlorophenylamino)ethyl)piperidin-4-ol. The obtained compound is a potent and selective IP agonist displaying a long duration of action.