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.     

Heat transfer of combined forced and natural convection from horizontal cylinder to air

Experimental investigations have been carried out for combined convective flows of air induced around uniformly heated, horizontal cylinders. Three cases of aiding, opposing, and cross flows were examined. The experiments covered the ranges of the Reynolds and modified Rayleigh numbers of Re_d=50 to 900 and Ra_d^*=5×10⁴ to 3×10⁶. The flow fields around the cylinders were visualized with smoke. The results showed that separation points gradually shift from those of the forced convection to the top edge of the cylinder with increasing wall heat fluxes. The local heat transfer coefficients of the cylinders were also measured. Although the local coefficients show complex variations with the forced flow velocities and the wall heat fluxes, the overall coefficients become higher than those estimated from pure forced and natural convections throughout the cases of aiding, opposing, and cross flows. Moreover, it was confirmed that the overall Nusselt numbers as well as the separation points can be predicted with the non‐dimensional parameter (Gr_d^*/Nu_dRe_d²). © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(8): 474–488, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20180     

Change in the Status of Water in Japanese Noodles During and After Boiling Observed by NMR Micro Imaging

ABSTRACT: A correlation between moisture content (M, g water/ g dry matter) and transverse relaxation time ( T ₂) of water protons in standard wheat gel samples was established by NMR. Changes in moisture distribution in Japanese noodles were estimated from T ₂ of water protons obtained by NMR micro imaging using the correlation. Penetration of water from the surface to the core during boiling and homogenization of moisture content after boiling were clearly observed in the MR images and moisture profile. A local minimum of T ₂ of water protons was detected in the moisture profile of noodles boiled in tap water.     

Origin of sennosides in health teas including Malva leaves

The aim of this study is to clarify whether sennosides are contained in the leaf of Malva verticillata L., and then to clarify the source of sennosides in health teas including malva leaves. The identification and determination of sennosides were performed with thin layer chromatography and high performance liquid chromatography. The leaf of Malva verticillata L. did not contain sennosides A or B and could be easily distinguished from senna leaf. Our previous report showed that sennosides are contained in weight-reducing herbal teas including malva leaves, and that senna leaf is a herbal component in some teas. Furthermore, in 10 samples of health tea including malva leaves that were bought last year, the smallest amount of sennosides was 6.1 mg/bag, and all health teas including malva leaves contained the leaf and midrib of senna. We suggest that sennosides A and B are not contained in the leaf of Malva verticillata L., and that the sennosides in health teas including malva leaves are not derived from malva leaf but from senna leaf.     

Variable temperature neutron diffraction studies of single crystals of LiND2

We have synthesized a single crystal of lithium amide (LiNH₂, LiND₂) by melting method, and performed neutron diffraction of the single crystal at variable temperature. LiND₂ is tetragonal structure and I-4 space group. Lattice parameters and unit cell volume of LiND₂ at room temperature, 50 °C, 100 °C, 150 °C and 200 °C were determined. Both of the lattice parameters and the unit cell volume increase with increase of temperature. From these results, we have estimated coefficient of volumetric thermal expansion α_V of LiND₂ to be 222 × 10⁻⁶/K. With increase of temperature, all thermal ellipsoids gradually expand because of thermal vibration.     

Hydrogen absorption of catalyzed magnesium below room temperature

Hydrogen absorption of magnesium (Mg) catalyzed by 1 mol% niobium oxide (Nb₂O₅) was demonstrated under the low temperature condition even at −50 °C. The kinetic and thermodynamic properties were examined for MgH₂ with and without Nb₂O₅. By considering the remarkable absorption features at such low temperature, the essential hydrogen absorption properties were investigated under accurate isothermal conditions. As the results, the activation energy of hydrogen absorption for the catalyzed Mg was evaluated to be 38 kJ/mol, which was significantly smaller than that of MgH₂ without the catalyst. The kinetic improvement was also found on the hydrogen desorption process. On the other hand, thermodynamic properties were not changed by the catalyst as a matter of course. Therefore, the Nb₂O₅ addition mainly affects the reaction rates between Mg and hydrogen and shows the excellent catalytic effects.     

Discussion on the equivalent conductivity and resistance of stress corrosion cracks in eddy current simulations

This study evaluates the numerical modeling of stress corrosion cracks from the viewpoint of eddy current simulations. Five stress corrosion cracks are artificially introduced into austenitic stainless steel plates measuring 25 mm in thickness, and then eddy current inspections are conducted to gather eddy current signals and destructive tests performed to confirm the true profiles of the cracks. The cracks are carefully introduced so as not to cluster, and the data obtained enables discussion of the modeling of a single crack quantitatively. Subsequent numerical simulations model each crack as a rectangular region with a fixed width and uniform conductivity, and evaluate the equivalent width and conductivity suitable for modeling the crack. The evaluation reveals that it is not reasonable to correlate the size of a crack and only its width or conductivity, and larger cracks tend to have greater resistance, which is defined as the width divided by conductivity. Furthermore, the values of width and conductivity depend also on the exciting frequency and probe used; however, the resistance remains almost unchanged by the experimental condition.     

Comparison of enteral nutrition with combined enteral and parenteral nutrition in post-pancreaticoduodenectomy patients: a pilot study

Background  

Many clinical studies have demonstrated that early postoperative enteral nutrition (EN) improved the postroperative course. Post-pancreaticoduodenectomy (PD), patients tend to suffer from postoperative nausea, abdominal distention, and diarrhoea, causing difficulty in the introduction of EN. In this pilot study, we investigated the appropriate nutritional mode post-pancreatic surgery.     

Characteristics of the thiobarbituric acid reactivity of oxidized fats and oils

The thiobarbituric acid (TBA) reactivity of oxidized methyl linoleate, soybean oil, sesame oil, lard, chicken oil and sardine oil was characterized by using four different methods with 0.01% butylated hydroxytoluene (BHT). Optimal pH for the reactivity of most of the oxidized samples was 3–4, and that of some samples was above 5. Introduction of 2 mMt-butyl hydroperoxide (t-Bu00H) or 0.2 mM ferric ion in the reaction markedly enhanced the reactivity. Introduction of 0.2 mM ethylenediamine tetraacetic acid suppressed the reactivity. The characteristics of the TBA-reactivity of the samples were similar to those of alkadienals or alkenals. The most preferable method for the estimation of the TBA-reactive substances of the oxidized fats and oils was that using solvents at pH 3.5 with introduction of BHT, andt-Bu00H or ferric ion.     

Preparation and properties of carbon dental implant with fine rahmen surface layer

Blade- and tooth-root-form carbon dental implants were prepared by fixing fine Rahmen surface (FRS) layers of carbon fabric on a carbon fiber-reinforced carbon (CFRC) core. The fixing was successfully performed through the low-temperature deposition of pyrolytic carbon using cis-1,2-dichloroethylene as the raw material. The resultant implants showed flexural and compressive strength more than 150 and 100 MPa, respectively. The outer part of this FRS layer contained many pores ranging from 30 to 300 μm in diameter and 40–75% in volume fraction.New bone was generated in the open pores after being embedded in the femur of a monkey for 6 months. The shear strength of the embedded implant vs bone interface was 15 MPa. On the other hand, the blade-form FRS implant in the mandible of a monkey gave a locking system consisting of “bone-collagen fiber-calcified layer” after two years under a masticating pressure. The latter is very similar to the natural tooth system.