Four coumarins from Heracleum yunngningense

Four new coumarins (1-4) were isolated from the roots of Heracleum yunngningense HAND.-MASS. Their structures were established by spectral analyses.     

Variations in Photosystem I Properties in the Primordial Cyanobacterium Gloeobacter violaceus PCC 7421

We compared the optical properties of the trimeric photosystem (PS) I complexes of the primordial cyanobacterium Gloeobacter violaceus PCC 7421 with those of Synechocystis sp. PCC 6803. Gloeobacter violaceus PS I showed (1) a shorter difference maximum of P700 by approximately 2 nm, (2) a smaller antenna size by approximately 10 chlorophyll (Chl) a molecules and (3) an absence of Red Chls. The energy transfer kinetics in the antennae at physiological temperatures were very similar between the two species due to the thermal equilibrium within the antenna; however, they differed at 77 K where energy transfer to Red Chls was clearly observed in Synechocystis sp. PCC 6803. Taken together with the lower P700 redox potential in G. violaceus by approximately 60 mV, we discuss differences in the optical properties of the PS I complexes with respect to the amino acid sequences of core proteins and further to evolution of cyanobacteria.     

Dynamic molecular movements and aggregation structures of lipids in a liquid state

This paper discusses the molecular conformations and the liquid structures of triacylglycerols (TGs) and fatty acids in their melts. Three models for liquid state ordering have been proposed for TG melts to date: the smectic liquid crystal model, the nematic liquid crystal model, and the discotic model. To completely resolve the liquid structure of TGs, further research is required. However, some information on the molecular level has been obtained for fatty acids that are relatively simple compounds. The combination of various spectroscopic and thermodynamic measurements revealed that the hydrogen-bonded dimers of fatty acids are units of intermolecular and intramolecular movements in the liquids and in non-polar solvents. The dimers that construct the clusters resemble the smectic liquid crystal and determine the physicochemical properties of the liquid of the fatty acid. Cholesterol stabilizes the clusters, while ethanol destroys them. Self-diffusion and neutron diffraction measurements revealed that two kinds of fatty acids exist in their binary liquid mixture exist as the homodimers composed of same species.     

Synthesis and photophysical properties of 8-arylbutadienyl 2′-deoxyguanosines

We have developed novel push-pull-type 8-arylbutadienyl 2′-deoxyguanosine derivatives, ^ABG (1a) and ^CBG (1b). These nucleosides exhibit strong solvent polarity dependent fluorescence emission at long wavelength (ca. 490-550 nm). These environmentally sensitive fluorescent deoxyguanosines are powerful tools for structural studies of nucleic acids and also in molecular diagnostics.     

Bulk-type all-solid-state batteries with mechanically prepared LiCoPO4 composite cathodes

Journal of Solid State Electrochemistry - All-solid-state Li batteries are suitable for the application of 5 V-class cathode materials that can provide high energy densities. However, it is hard to...     

Monte Carlo simulation of a cluster model for the chirality conversion of crystals with grinding

By means of Monte Carlo simulation of a cluster model, we study statistical aspect of the chirality conversion of crystals. The chirality conversion is known to occur in a saturated solution by grinding crystals, and the enantiomeric excess increases exponentially. In the simulation, with crystallization and dissolution of monomers alone, the behavior of the enantiomeric excess observed in experiment cannot be reproduced although the homochirality is realized as a result of statistical fluctuation. By allowing crystallization and dissolution of dimers, the exponential amplification of enantiomeric excess can be realized.     

A bayesian approach to the probability density estimation

Summary A Bayesian procedure for the probability density estimation is proposed. The procedure is based on the multinomial logit transformations of the parameters of a finely segmented histogram model. The smoothness of the estimated density is guaranteed by the introduction of a prior distribution of the parameters. The estimates of the parameters are defined as the mode of the posterior distribution. The prior distribution has several adjustable parameters (hyper-parameters), whose values are chosen so that ABIC (Akaike's Bayesian Information Criterion) is minimized. The basic procedure is developed under the assumption that the density is defined on a bounded interval. The handling of the general case where the support of the density function is not necessarily bounded is also discussed. The practical usefulness of the procedure is demonstrated by numerical examples. The Institute of Statistical Mathematics     

Conformational aspects of caryophyllene. Population of stable conformers and ring inversion barrier of trans cyclononene ring portion

Cmr measurements of caryophyllene revealed two major conformers equilibrating in a ratio 76:24 at room temperature. The energy ordering of four possible conformers of caryophyllene predicted by molecular mechanics calculations agrees well with the experimental observation. The barrier of interconversion between the two conformers was determined as 16.25 kcal/mol.     

Molecular self-assembling of chiral and racemic butan-2-ol in carbon tetrachloride solutions

The self-association of (R)-, (S)- and (RS)-butan-2-ol in their carbon tetrachloride solutions was studied through the mid-infrared (mid-IR) and near-infrared (NIR) spectroscopic observations. The mid-IR and NIR spectra for each chiral butan-2-ol were compared with those for the racemic (RS)-butan-2-ol. Although it has been reported that the hydrogen bonding among the chiral butan-2-ol molecules was stronger than that among the racemic ones, any distinguishable differences between the chiral and the racemic butan-2-ol in CCl₄ solution or even in their pure liquid state were not observed both in their mid-IR and NIR spectra. A superior analytical method, assuming a successive association process for the alcohol molecules, was applied to the analysis of the sharp band at 3630 cm⁻¹ (the OH-stretching vibration mode attributed to free OH-monomer) for the (R)-, (S)- or (RS)-butan-2-ol in CCl₄. The mean association number N for each alcohol increased with increasing in concentration until 0.12 mol dm⁻³ and then becomes constant (about four). On the other hand, Zanker's plotting method, assuming an equilibrium between monomers and only one kind of polymer species, was also applied to the analysis of the above spectroscopic results; the association number n evaluated from the Zanker's method fairly agreed with the N value in the concentration region of 0.12–0.60 mol dm⁻³.