Polycatenar mesogens with a perfluorinated moiety showing a variety of liquid crystalline polymorphism

Polycatenar materials composed of a four-aromatic-ring core, with either a bulky or end-branched perfluorinated moiety attached at one end through a methylene spacer group, and three peripheral alkoxy chains of varying length (the carbon number n = 4, 6, 8, 10, 12, 14, 16) on the other end-ring, were synthesized to investigate the roles of the chemical structure of the compositional segments in relation to liquid crystalline phase formation. It was found that a homologous series of polycatenar materials exhibited a variety of liquid crystalline phases strongly dependent on the length of the peripheral alkyl chains. Moreover it was shown that changes in the spacer group and in the structure of the perfluorinated segment had a significant influence on mesophase formation.     

Magneto-Optical Measurement of Organic Conductor Using Rotational Cavity System

We have developed a new magneto-optical measurement system using a rotational cavity system equipped with a millimeter vector network analyzer and a 14 T solenoid type super conducting magnet. The measurement can be performed in the transmission configuration down to 1.6 K. The results of the precise angular dependence measurement of quasi-one-dimensional organic conductor (DMET)₂I₃ using the new system are shown, and its Fermi surface will be discussed in connection with the previous reports.     

Tensor analyzing power T 20 of the dd → 3Hen and dd → 3Hp reactions at zero angle for energies 140, 200, and 270 MeV

RIKEN Accelerator Research Facility data on the tensor analyzing power T ₂₀ of the dd → ³Hen and dd → ³Hp reactions at zero angle for deuteron kinetic energies of 140, 200, and 270 MeV are reported. The observed positive sign of T ₂₀ clearly demonstrates the sensitivity to the D/S-wave ratio in the ³He and ³H wave functions in the energy range of the experiment. Data on T ₂₀ for the ³Hen channel are in agreement with those for the ³Hp channel within the experimental errors.     

Isotope dilution analysis of selenite and selenate in natural water using microwave-induced nitrogen plasma mass spectrometry.

Isotope dilution analysis of the sub-microg l(-1) levels of selenite and selenate in natural water samples by microwave-induced nitrogen plasma mass spectrometry (MIP-MS) was performed. An appropriate amount of a spike solution containing 78Se-selenite and 78Se-selenate was added to the natural water sample to be analyzed. Both analytes in the water were then concentrated simultaneously by passing the sample through a column that was filled with an anionic exchange resin. After the concentration process, all of the selenite and some of the selenate on the resin were eluted by 0.03 M nitric acid. The residual selenate was eluted by 0.13 M nitric acid. The eluted sample solutions were injected into MIP-MS, and isotope dilution analyses were carried out. Selenite and selenate concentrations as low as 0.01 microg l(-1) in the natural water sample were successfully determined by the proposed method.     

Simple and rapid determination of trace amounts of gold(III), palladium(II), and platinum(IV) in industrial waste solutions after recovery of noble metals by combined use of GFAAS and anion-exchange separation.

A simple and rapid method for the analysis of trace amounts of gold(III), palladium(II), and platinum(IV) by the combined use of graphite furnace atomic absorption spectrometry and anion-exchange separation was proposed, and successfully applied to the rapid determination of metals in industrial waste solutions obtained from the final process of noble-metal recovery factories, because noble metals can be selectively and quantitatively separated to a high degree by using a small column containing only a 0.7 g-portion of a common anion-exchange resin and a dilute thiourea solution.     

Comparison of the umbrella sampling and the double decoupling method in binding free energy predictions for SAMPL6 octa-acid host–guest challenges

We calculate the absolute binding free energies of tetra-methylated octa-acids host–guest systems as a part of the SAMPL6 blind challenge (receipt ID vq30p). We employed two different free energy simulation methods, i.e., the umbrella sampling (US) and double decoupling method (DDM). The US method was used with the weighted histogram analysis method (WHAM) (US-WHAM scheme). In the DDM scheme, Hamiltonian replica-exchange method (HREM) was combined with the Bennett acceptance ratio (BAR) (HREM-BAR scheme). We obtained initial binding poses via molecular docking using GalaxyDock-HG program, which is developed for the SAMPL challenge. The root mean square deviation (RMSD) and the mean absolute deviations (MAD) using US-WHAM scheme were 1.33 and 1.02 kcal/mol, respectively. The MAD was the top among all submissions, however the correlation with respect to experiment was unexceptional. While the RMSD and MAD via HREM-BAR scheme were greater than US-WHAM scheme, (i.e., 2.09 and 1.76 kcal/mol), their correlations were slightly better than US-WHAM. The correlation between the two methods was high. Further discussion on the DDM method can be found in a companion paper by Han et al. (receipt ID 3z83m) in the same issue.     

Total Synthesis of 11‐Saxitoxinethanoic Acid and Evaluation of its Inhibitory Activity on Voltage‐Gated Sodium Channels

11‐Saxitoxinethanoic acid (SEA) is a member of the saxitoxin (STX) family of paralytic shellfish poisons, and contains an unusual C?C bond at the C11 position. Reported herein is a total synthesis of SEA. The key to our synthesis lies in a Mukaiyama aldol condensation reaction of silyl enol ether with glyoxylate in the presence of an anhydrous fluoride reagent, [Bu₄N][Ph₃SnF₂], which directly constructs the crucial C?C bond at the C11 position in SEA. The Na_VCh‐inhibitory activities of SEA and its derivatives were evaluated by means of cell‐based assay. SEA showed an IC₅₀ value of (47±12) nm , which is approximately twice as potent as decarbamoyl‐STX (dcSTX).