Synthesis of the BC/DE ring model of brevisin for confirmation of the structure around the acyclic junction

Synthesis of the BC/DE ring model of brevisin, a polycyclic ether isolated from the red tide dinoflagellate Karenia brevis, is reported. Comparison of the NMR data of the BC/DE ring model with those corresponding to the same region of brevisin led to the confirmation of its structure around the acyclic juncture.     

Substituent effect on electrophoretic mobility for a series of poly(N-acryloyl-amino acid)s

In this study, the electrophoretic mobilities (μ) for a series of poly(N-acryloyl-amino acid)s were determined by capillary zone electrophoresis to investigate the effect of substituent on the electrophoretic behavior of polyelectrolytes. The μ values determined showed a strong correlation with the molar volume of the corresponding amino acids.     

G protein subtype specificity of rhodopsin intermediates metarhodopsin Ib and metarhodopsin II

Rhodopsin is one of the members of the G protein-coupled receptor family that can catalyze a GDP–GTP exchange reaction on the retinal G protein transducin (Gt) upon photon absorption. There are at least two intermediate states, meta-Ib and meta-II, which exhibit direct interaction with Gt. Meta-Ib binds to GDP-bound Gt, while meta-II forms a complex with Gt having no nucleotide, suggesting that meta-Ib is a state that initially interacts with Gt. Here we investigated whether or not meta-Ib exhibits specific interaction with G protein similar to meta-II, by examining the binding efficiencies of meta-Ib and meta-II to Giα and its mutants whose C-terminal 11 amino acids were replaced with those of Goα, Gqα and Gsα. The affinity of meta-Ib to the C-terminal 11 amino acids of Gtα was similar to those of Giα and its mutant with Goα's C-terminal 11 amino acids, whereas meta-II exhibited affinity to the C-terminal 11 amino acids of Giα mutant with Goα's C-terminal 11 amino acids about half of what was seen for Gtα and Giα. Both intermediates exhibited no affinity to the Giα mutants containing the C-terminal 11 amino acids of Gqα and Gsα. These results suggested that meta-Ib is the state that exhibits specific interaction with G protein as meta-II does, although meta-Ib exhibits a slightly lenient binding selectivity compared to that of meta-II.     

Numerical and experimental study on the wave attenuation in bone--FDTD simulation of ultrasound propagation in cancellous bone

In cancellous bone, longitudinal waves often separate into fast and slow waves depending on the alignment of bone trabeculae in the propagation path. This interesting phenomenon becomes an effective tool for the diagnosis of osteoporosis because wave propagation behavior depends on the bone structure. Since the fast wave mainly propagates in trabeculae, this wave is considered to reflect the structure of trabeculae. For a new diagnosis method using the information of this fast wave, therefore, it is necessary to understand the generation mechanism and propagation behavior precisely. In this study, the generation process of fast wave was examined by numerical simulations using elastic finite-difference time-domain (FDTD) method and experimental measurements. As simulation models, three-dimensional X-ray computer tomography (CT) data of actual bone samples were used. Simulation and experimental results showed that the attenuation of fast wave was always higher in the early state of propagation, and they gradually decreased as the wave propagated in bone. This phenomenon is supposed to come from the complicated propagating paths of fast waves in cancellous bone.     

Sensitivity of a miniaturized touch probe sensor using PZT thin film vibrator

In this paper, an improved touch probe sensor device for higher sensitivity and low contact force is reported. In order to improve the resolution, we have evaluated the sensitivity and fabricated a miniaturized sensor. The sensor transducer was 3 mm long and had higher resonance frequency. The resonance frequency of the vibrator was 937 kHz. Evaluated sensitivity was 1.0 x 10(-1) mV/nm. This value equals five times larger than that of a previous sensor. Miniaturization of the sensor device carried smaller vibration operation and higher sensitivity.     

Hydrogen-bond assisted enormous broadening of infrared spectra of phenol-water cationic cluster: an ab initio mixed quantum-classical study

The infrared spectrum of phenol-water cationic cluster, [PhOH.H2O]+, taken by Sawamura et al. [J. Phys. Chem. 100, 8131 (1996)] is puzzling in that the peak due to the stretching mode of the phenolic OH (3657 cm-1 for a neutral monomer and 3524 cm-1 for PhOH.H2O) seemingly disappears and instead an extremely broad tail extending down to 2900 cm-1 is observed. The present authors theoretically ascribe this anomalous spectrum to an inhomogeneous broadening of the OH stretching peak caused by the hydrogen bond, the strength of which has been greatly enhanced by ionization of the phenyl ring. Indeed they estimate that the peak position is at 2300 cm-1 and the spectral width can become as wide as 1000 cm-1 at the cluster energy of 32 kcal/mol. This surprisingly wide broadening can be generic in hydrogen-bond systems, which in turn is useful to study the nature of the hydrogen-bond assisted dynamics in various systems such as those in DNA and proteins. To study the present system quantitatively, the authors have developed an ab initio mixed quantum-classical method, in which the nuclear motions on an adiabatic ab initio potential surface are treated such that only the OH stretching motion is described quantum mechanically, while all the other remaining modes are treated classically with on-the-fly scheme. This method includes the implementation of many numerical methodologies, which enables it to deal with a relatively large molecular system. With this theoretical method, the authors analyze the present anomalous broadening in a great detail. In particular, they suggest that one can extract direct information about the hydrogen-bond dynamics with respect to the clear correlation between the vibrational excitation energy of the OH stretching and intermolecular distance by means of a time-resolved infrared spectroscopy: Reflecting the slow and wide-range variation of the intermolecular distance of the relevant hydrogen bond, the time-resolved spectrum is predicted to vary (shift) largely covering the wide range of frequency domain. Thus, it is found that the short-time average along a selected trajectory sensitively reflects the change of the intermolecular distance. The authors also study the effect of internal energy on the hydrogen bonding and the OH spectrum.     

Evaluation of the energy loss of intense pulsed ion beam in thinfoil targets

A new and simple method is proposed to evaluate the energy deposition profile of an intense pulsed ion beam in the target by using a magnetic energy spectrometer. Energy deposition profiles of protons in the cold targets are evaluated by this method, and good agreement has been obtained with the theoretical curves     

Charge separation at the rutile/anatase interface: a dominant factor of photocatalytic activity

Epitaxial and polycrystalline anatase films were grown by pulse-powered magnetron sputtering. The photoreduction of Ag ions showed the difference in the distribution of the photocatalytic active sites in these films. The polycrystalline anatase film was covered with an Ag layer. In contrast, discrete Ag particles were interspatially deposited on the epitaxial anatase film. Evaluation of the epitaxial film by micro-Raman spectrometry revealed that the rutile coexisted at only the site where the Ag particle was precipitated. These results suggest that the rutile/anatase interface is the active site for photocatalysis and is one of the dominant factors of the photocatalytic activity.     

Elucidating 2D Charge-Density-Wave Atomic Structure in an MX–Chain by the 3D-ΔPair Distribution Function Method**

Many solids, particularly low-dimensional systems, exhibit charge density waves (CDWs). In one dimension, charge density waves are well understood, but in two dimensions, their structure and their origin are difficult to reveal. Herein, the 2D charge-density-wave atomic structure and stabilization mechanism in the bromide-bridged Pd compound [Pd(cptn)₂Br]Br₂ (cptn=1R,2R-diaminocyclopentane) is investigated by means of single-crystal X-ray diffraction employing the 3D-Δpair distribution function (3D-ΔPDF) method. Analysis of the diffuse scattering using 3D-ΔPDF shows that a 2D-CDW is stabilized by a hydrogen-bonding network between Br⁻ counteranion and the amine (NH₂) group of the cptn in-plane ligand, and that 3D ordering is prevented due to a weak plane to plane correlation. We extract the effective displacements of the atoms describing the atomic structure quantitatively and discuss the stabilization mechanism of the 2D-CDW. Our study provides a method to identify and measure the key interaction responsible for the dimensionality and stability of the CDW that can help further progress of rational design.