Effects of amino acid replacements around the reactive site of chicken ovomucoid domain 3 on the inhibitory activity toward chymotrypsin and trypsin

We have previously shown that replacing the P1-site residue(Ala) of chicken ovomucoid domain 3 (OMCHI3) with a Met or Lysresults in the acquisition of inhibitory activity toward chymotrypsinor trypsin, respectively. However, the inhibitory activitiesthus induced are not strong. In the present study, we introducedadditional amino acid replacements around the reactive siteto try to make the P1-site mutants more effective inhibitorsof chymotrypsin or trypsin. The amino acid replacement AspTyrat the P2' site of OMCHI3(P1Met) resulted in conversion to a35000-fold more effective inhibitor of chymotrypsin with aninhibitor constant (K_i) of 1.17x10^–11 M. The K_i valueof OMCHI3(P1Met, P2'Ala) indicated that the effect on the interactionwith chymotrypsin of removing a negative charge from the P2'site was greater than that of introducing an aromatic ring.Similarly, enhanced inhibition of trypsin was observed whenthe AspTyr replacement was introduced into the P2' site of OMCHI3(P1Lys).Two additional replacements, AspAla at the P4 site and ArgAlaat the P3' site, made the mutant a more effective inhibitorof trypsin with a K_i value of 1.44x10^–9 M. By contrast,ArgAla replacement at the P3' site of OMCHI3(P1Met, P2'Tyr)resulted in a greatly reduced inhibition of chymotrypsin, andAspAla replacement at the P4 site produced only a small changewhen compared with a natural variant of OMCHI3. These resultsclearly indicate that not only the P1-site residue but alsothe characteristics, particularly the electrostatic properties,of the amino acid residues around the reactive site of the proteaseinhibitor determine the strength of its interactions with proteases.Furthermore, amino acids with different characteristics arerequired around the reactive site for strong inhibition of chymotrypsinand trypsin.     

One-step formation of ethyl methyl ketone from 1-butene and water on ultrastable Y-type zeolite catalyst

Proton exchanged ultrastable Y-type zeolite with silica/alumina = 40 showed a pronounced catalytic activity for the formation of ethyl methyl ketone directly from 1-butene and water. The formation rate of ethyl methyl ketone was much higher than those on MoO₃-based catalysts in the oxidation of 1-butene by oxygen. It was suggested that the basic site necessary for the formation of ethyl ketone directly from 1-butene and water would be the pentacoordinated Al.     

Electro-rheological effect and dynamic rheological properties of a blend composed of two liquid crystalline materials with different molecular weight

Electro-rheological (ER) effect of a blend composed of two liquid crystalline materials with different molecular weights is described in this article. The results indicated that ER effect of the blend was observed at the temperature range where each neat sample did not show ER effect. Furthermore, both storage modulus (G′) and loss modulus (G″) decreased drastically at the temperature range for the blend in dynamic viscoelastic measurements. We show that steady ER effect could be obtained by using a blend made up of two liquid crystalline components, whereas remarkable increment in shear stress was not observed for each component under applied electric field.     

Change in the molecular weight distribution of poly(ethylene oxide) caused by the complexation with poly(acrylic acid)

The complexation between poly(ethylene oxide) (PEO) and poly(acrylic acid) (PAA) was made by using double the molar quantity of either polymer component at pH 2 where the resulting complex completely precipitates. After the removal of the precipitate, PEO or PAA remaining in the supernatant was subjected to gel permeation chromatography to investigate the change in the molecular weight distribution (MWD) caused by the complexation. No remarkable difference is observed in the MWD curves for PEO[1] (M_w=1.37 × 10⁴) before and after the complexation with PAA[1] (M_w=1.10 × 10³) and PAA[2] (M_w=4.16 × 10⁵). However, the MWD curves of PEO[2] (M_w=1.26 × 10⁵) and PAA[2] become shortened and shift to the low molecular weight side after the complexation with PAA[1] or [2] and PEO[2], respectively. This tendency is enhanced by increasing the complexation temperature. From these results, it is indicated that the complexation between PEO and PAA deals with an equilibrium reaction, and the equilibrium constant is dependent on the chain length of both polymer components and also on the complexation temperature.     

Additional kernel observer: privilege escalation attack prevention mechanism focusing on system call privilege changes

International Journal of Information Security - Cyberattacks, especially attacks that exploit operating system vulnerabilities, have been increasing in recent years. In particular, if administrator...     

Effect of Computational Constraints on Zero-Dimensional Computations for the Nanosecond-Order Ignition Process of the CH4/Air Mixture

Combustion, Explosion, and Shock Waves - Zero-dimensional computations of nanosecond-order ignition using a nanosecond discharge are performed with two constraints. The effects of these constraints...     

Experimental design to evaluate properties of electrospun fibers of zein/poly (ethylene oxide) for biomaterial applications

The production of polymer fibers from the combination of zein and PEO might have great potential in the field of biomaterial. Zein/PEO fibers were obtained in this work through solution electrospinning. An experimental design, 2^4-1, was used for evaluating the influences of PEO content in the blend, distance from the needle tip to the collector, applied electric voltage and solution flow for average fiber diameter and relative-yield process. Beyond this, the relationship between PEO content in the blend and the fiber properties were evaluated through FTIR, DSC, TG, tensile tests, and cytotoxic tests. The factor that exerts the greatest effect on the average fiber diameter response was the electrical voltage. The increase in PEO content in the blend decreased the thermal stability and increased the degree of the fibers' crystallinity. The mechanical tests showed that fibers with higher elongation were obtained at richer PEO blends. The fibers presented cytocompatible characteristics.     

Ni含量对TiNi形状记忆合金相变行为的影响

用示差扫描热分析仪和光学显微镜系统研究了Ｎｉ含量对ＴｉＮｉ形状记忆合金Ｒ相和Ｍ相相变温度，相变热，热滞的影响。结果表明：在加热和冷却过程中，Ｔｉ－３３．３％Ｎｉ和Ｔｉ－７５．０％Ｎｉ不发生相变；ＴＭ，ΔＭ，ΔＨＭ和ΔＨＲ是Ｎｉ是含量的函数，ＴＲ和ΔＲ基本为一定值，与Ｎｉ含量有关。     

Hydrogen absorption characteristics of Pd1−xLix (x = 0.055 and 0.072) alloys and ordered Pd7Li

Thermodynamic quantities were determined for the absorption of hydrogen in Pd-5.5at.%Li and Pd-7.2at.%Li alloys, the latter alloy being in the two-phase field of saturated -Pd(Li,s) solid solution and the ordered Pd₇Li phase. Data were also determined for the Pd-10.6at.%Li alloy which consists only of the ordered Pd₇Li phase. The data were determined from measurements of pressure-composition isotherms at temperatures between 273 K and 463 K and hydrogen pressures up to 1000 Torr. The Pd---Li alloys dissolve considerable amounts of hydrogen and form a more stable hydride phase than Pd despite the lattice contraction which occurs on alloying Pd with Li. The hydrogen solubility in the ordered Pd₇Li phase alone is a little smaller than that in the two-phase mixture. The large hydrogen absorption of Pd---Li alloys, which does not depend on the presence of ordered Pd₇Li, may be attributed to (i) an attractive H---Li pair interaction, (ii) a decrease in the strain energies necessary for hydrogen occupation of the interstices, because of the similar lattice parameters of the -Pd(Li,s) and ordered Pd₇Li phases, and the large compressibility of Pd---Li alloys, and (iii) the valence of 1 of Li in Pd compared with 3 for, for example, Y in Pd.     

A new refining process for iron oxide using iron ore and its application to hard ferrites

Kawasaki Steel Corporation and Kawatetsu Mining Co., Ltd. have developed a new refining process to extract iron oxide from iron ore to meet the increase in demand for iron oxide for high- grade hard ferrites. This article discusses the quality of iron oxides and the characteristics of the hard ferrite magnets produced from them.