Sedimentation equilibrium study on preferential interaction of protein with solvent components

A sedimentation equilibrium equation was derived in weight-per-volume concentration units to evaluate the degree of preferential binding of one solvent component to a homogeneous neutral macromolecule in a mixture of two components. Using the equation, the preferential binding of chloroethanol to β-lactoglobulin A was calculated from sedimentation equilibrium data, and the result showed good agreement with values obtained by light scattering and refractive index increment experiments. It was also demonstrated that the preferential interaction can in principle be determined by density increment measurements under different conditions: at constant molality and at constant chemical potential of solvent.     

Free energy perturbation study on a Trp-binding mutant (Ser88 ->Cys) of the trp-repressor

The Ser⁸⁸Cys mutant of the trp-repressor showed a lower affinityfor the corepressor than the wild-type repressor [G = 1.7 ±0.3 kcal/mol, Chou and Matthews (1989) J. Biol. Chem., 264,18314–18319].A molecular dynamics/free energy cycle perturbation study wasperformed to understand the origin of the decreased affinity.A value (G = 1.58 ± 0.28 kcal/mol) comparable with theexperimental value was obtained by the simulation. Free energycomponent analysis revealed that destabilization of the vander Waals interaction between Ser⁸⁸ and Trp¹⁰⁹ (corepressor)mainly contributed to the decreased affinity of the mutant.The rotational transition of the hydroxyl (sulfhydryl) groupof Ser⁸⁸ (Cys⁸⁸) during the simulations affected the contributionsof Arg⁸⁴ and water to the free energy change in the aporepressorand those of Arg⁸⁴ and Trp ¹⁰⁹ to that in the holorepressor.However, the contributions from different residues compensatedeach other, and the total free energy changes were almost invariablein the various simulations.     

Synthesis, structure and mechanical properties of Zr-Cu-based bulk metallic glass composites

The unusual glass-forming ability(GFA) of the Zr_(48)Cu_(36)Ag_8Al_8 alloy and the high ductility of the Zr_(48)Cu_(36)Ag_8Al_8 metallic glass-matrix composites containing Ta powder were reported.The bulk metallic glass rod with a diameter of 25 mm was successfully synthesized using copper mold casting for the Zr_(48)Cu_(36)Ag_8Al_8 alloy.High GFA of this alloy was found to be related to a large supercooled liquid region and a quaternary eutectic point with low melting temperature.The bulk metallic glass...     

Synthesis of diameter-controlled carbon nanotubes using centrifugally classified nanoparticle catalysts

Iron-based nanoparticles, centrifugally classified by size, with variation of subnanometer order, have been used for the growth of diameter-controlled carbon nanotubes (CNTs) for the first time via catalytic chemical vapor deposition. The centrifugal classification of nanoparticles is facilitated by fractional precipitations through the sequential addition of ethanol to a hexane solution containing the nanoparticles. Three different nanoparticle sizes were obtained, which have average diameters and standard deviations of 3.9 ± 0.8 nm, 3.3 ± 0.6 nm, and 2.8 ± 0.4 nm. By the classification process of nanoparticles, the standard deviation of the average diameter of the fractionated nanoparticles decreased by around one half of that of the as-synthesized nanoparticles. In addition, we demonstrate a technique for estimating the average diameter of each classified nanoparticle using conventional low-angle X-ray diffraction, without the need for time-consuming TEM observation and analysis. From the three classified nanoparticle sizes, with average diameters of 2.8, 3.3, and 3.9 nm, CNTs with average diameters of 3.1, 3.6, and 4.5 nm were obtained by changing growth temperatures, respectively. Therefore, centrifugally classified nanoparticles are one of the most promising ‘seeds’ for use in the diameter-selective growth of CNTs.     

Novel synthesis of microcrystalline titanium(IV) oxide having high thermal stability and ultra-high photocatalytic activity: thermal decomposition of titanium(IV) alkoxide in organic solvents

Thermal decomposition of titanium(IV) tetra-tert-butoxide (TTB) in inert organic solvents at 573 K yielded microcrystalline anatase (titanium(IV) oxide, TiO₂) powders with a crystallite size of ca. 9 nm and a surface area of <100 m² g^-1. Primary and secondary alkoxides of titanium(IV), however, were not decomposed under similar conditions, indicating that the thermal stability of C-O bonds in the alkoxides was a decisive factor for their decomposition. The TiO₂ prepared from TTB by this manner was thermally stable upon calcination in air and retained high surface area of ca. 100 m² g^-1 even after calcination at 823 K. The as-prepared TiO₂ powders, without calcination, exhibited much higher rate of carbon dioxide formation than any other active photocatalysts such as Degussa P-25 and Ishihara ST-01 in the photocatalytic mineralization of acetic acid in aerated aqueous solutions. The higher activity of the present TiO₂ photocatalysts is attributed to both high crystallinity and large surface of the present product. The calcination of the as-prepared TiO₂ in air reduced the photocatalytic activity, but it was still higher than the other commercially available TiO₂'s. This revised version was published online in July 2006 with corrections to the Cover Date.     

Reactive blending of polyamide with polyethylene: pull-out of in situ-formed graft copolymers and its application for high-temperature materials

Reactive blending of polyamide 6 (PA) with polyethylene (PE) having reactive sites, maleic anhydride (MAH content=0.1 wt%),and glycidyl methacrylate (GMA content=3-12 wt%), was carried out at 70/30 and 65/35 (PA/PE) blend ratios. Blend morphology evolved by reactive blending was analyzed by light scattering and transmission electron microscopy. The blends were then irradiated by electron beam. The degree of crosslinking was estimated by measuring the dynamic storage modulus at a temperature above melting point of PA. It was found that surface-to-surface interparticle distance τ was significantly reduced by the micelle formation via pull-out of in situ-formed graft copolymers. The blend with shorter τ was crosslinked by electron-beam irradiation at the lower dose level. A blend having the minimum τ (∼0.2 μm) was nicely crosslinked at a low dose level same as for PE, and even for the PA matrix system.     

Pervaporation via silicon-based membranes: Correlation and prediction of performance in pervaporation and gas permeation

Pervaporation (PV) is a membrane technology that holds great promise for industrial applications. To better understand the PV mechanism, PV dehydrations of various types of organic solvents (methanol, ethanol, iso-propanol, tert-butanol, and acetone) were performed on five types of organosilica and two types of silicon carbide-based membranes, all with different pore sizes. Water permeance was dependent on the types of organic aqueous solutions, which suggested that organic solvents penetrated the pores and hindered the permeation of water. In addition, water permeance of various types of membranes in PV was well correlated with hydrogen permeance in single-gas permeation. Furthermore, a clear correlation was obtained between the permeance ratio in PV and that in single-gas permeation, which was confirmed via the modified-gas translation model. These correlations make it possible to use single-gas permeation properties to predict PV performance.     

Penetration treatment of plasma-sprayed ZrO2 coating by liquid Mn alloys

The penetration phenomena of liquid manganese (Mn) alloy into porous ZrO₂ (8 vvt % Y₂O₃) coating plasma sprayed on SS400 steel substrate was studied by heating in a vacuum atmosphere. The improvement in mechanical properties of the coating by heat treatment with liquid Mn alloys was examined. Liquid Mn alloys, such as Mn-Cu, Mn-Sn, and Mn-In, rapidly penetrated the coating and formed a chemical bond between the coating and the substrate. The densification of the ZrO₂ coating occurred when ZrO₂ particles were sintered with liquid Mn alloys that penetrated the porous coating. The dense coating was free of porosity, and its hardness increased after heat treatment with Mn alloys, compared with assprayed ZrO₂ coating. Moreover, the fracture toughness of the coating reached the same levels as those of sintered yttria-stabilized PSZ.     

Effect of strain rate on compressive behavior of a Pd40Ni40P20 bulk metallic glass

Mechanical deformation of Pd₄₀Ni₄₀P₂₀ was characterized in compression over a wide strain rate range (3.3×10⁻⁵ to 2×10³ s⁻¹) at room temperature. The compression sample fractured with a shear plane inclined 42 degree with respect to the loading axis, in contrast to 56 degree for the case of tension. This suggests the yielding of the material deviates from the classical von Mises yield criterion, but follows the Mohr-Coulomb yield criterion. Fracture stress as well as strain was found to decrease with increasing applied strain rate. The compressive stress (1.74 GPa) was also found to be higher than the tensile fracture stress at a quasi-static strain rate. Close examination of the stress–strain curves revealed that localized shear might have occurred at a compressive stress of about 1.4 GPa, much lower than the “apparent” yield stress of 1.74 GPa. However, the stress of 1.4 GPa for shear band initiation is almost the same as the fracture stress measured at a dynamic strain rate of 5×10² s⁻¹. These results suggested that the fracture of a bulk metallic glass is sensitive to the applied loading rate.     

Catastrophic chaos theory: predicting recovery of health or death

Recently, we revealed a standard pattern of a macroscopic molecular network for controlling morphogenetic processes such as the development of organs, including blast, mesoderm, heart, and hands during about sevenfold cell divisions and a standard bio-chemical clock like the circadian one (Naitoh in Artif Life Robot 13, 2008; Japan J Ind Appl Math 28(1), 2011; J Phys Conf Ser 344, 2012; Artif Life Robot 17, 2012) A network model derived logically based on experimental observations is described by a nonlinear differential equation for predicting time evolutions of six macroscopic molecular groups: three gene groups and three enzyme groups, which include promoting and suppressing factors. Here, the macroscopic model extended for also describing aging processes shows various types of cycles and reveals the physical condition for determining whether or not living beings such as humans can survive after getting ill. It is stressed that, after becoming ill, living systems with overly fast generation of information molecules such as various genes end in death, whereas relatively fast production of enzymes leads to recovery. This may also explain an essential feature underlying carcinogenic processes.