On the mechanism of the peroxidase-catalyzed oxygen-transfer reaction

We reported evidence that horseradish peroxidase (HRP) and chloroperoxidase (CPO) catalyze oxygen transfer from H2O2 to thioanisoles [Kobayashi, S., Nakano, M., Goto, T., Kimura, T., & Schaap, A. P. (1986) Biochem. Biophys. Res. Commun. 135, 166-171]. In the present paper, the reaction mechanism of this oxygen transfer is discussed. The oxidation of para-substituted thioanisoles by HRP compound II showed a large negative rho value of -1.46 vs. the sigma + parameter in a Hammett plot. These results are in accord with the formation of a cation radical intermediate in the rate-determining step. Hammett treatments for HRP- and CPO-dependent S-oxygenations did not provide unequivocal proofs to judge the reaction mechanism, because of the poor correlations for sigma + and sigma p parameters. Different behavior was found in kinetics and stereoselectivity between the two enzymes. Results in the present study and recent studies strongly suggested the formation of a cation radical intermediate. The oxygen atom would transfer by reaction of compound II and the cation radical intermediate. Although involvement of the cation radical was not confirmed in the CPO system, a similar mechanism was proposed for CPO.     

Conformational study of 13C-enriched fibroin in the solid state, using the cross polarization nuclear magnetic resonance method

Silk fibroin with the alanyl carboxyl carbon enriched with 13C was obtained by giving a diet containing 13C-enriched alanine to the larvae of Bombyx mori and Antheraea pernyi at the fifth instar. Sericin-free fibroin fibers were prepared from cocoons, and gut was made from the liquid silk in the gland. The final 13C content was about 13%. Cross polarization/magic angle sample spinning spectra at 25 MHz and 75 MHz were measured for each sample at different orientations. Spectra were simulated using the principal values and orientations of the shielding tensor in the alanine crystal. The results indicate that the beta-structure of the fibroin may be a little more flattened than the typical pleated sheet beta-structure.     

Formation of spray-dried powder of S-adenosyl-L-methionine

S-Adenosyl-L -methionine (SAM) is an essential metabolite in all living organisms. In clinical research, SAM has also been suggested as a chemotherapeutic agent in various diseases. The main problem of SAM is its instability at high temperatures, at neutral and alkaline pH, and in the presence of humidity. SAM retention in spray-dried powder was determined under various conditions of spray-drying. The highest SAM retention was obtained when maltodextrin (dextrose equivalent, DE, of 25) was used as the carrier solid with the SAM feed liquid at pH 4.0. The water content in the powder had a significant effect on the stability of SAM. SAM powder with lower water content exhibited higher stability.     

Analysis of Flow Phenomena in Gastric Contents Induced by Human Gastric Peristalsis Using CFD

This paper uses computational fluid dynamics to simulate and analyze intragastric fluid motions induced by human peristalsis. We created a two-dimensional computational domain of the distal stomach where peristalsis occurs. The motion of the gastric walls induced by an antral contraction wave (ACW) on the wall of the computational domain was well simulated using a function defined in this study. Retropulsive flow caused by ACW was observed near the occluded region, reaching its highest velocity of approximately 12 mm/s in the narrowest region. The viscosity of the model gastric contents applied in this study hardly affected the highest velocity, but greatly affected the velocity profile in the computational domain. The shear rate due to gastric fluid motion was calculated using the numerical output data. The shear rate reached relatively high values of approximately 20 s⁻¹ in the most occluded region. The shear rate profile was almost independent of the fluid viscosity. We also simulated mass transfer of a gastric digestive enzyme (pepsin) in model gastric content when peristalsis occurs on the gastric walls. The visualized simulation results suggest that gastric peristalsis is capable of efficiently mixing pepsin secreted from the gastric walls with an intragastric fluid.     

Changes in plasma thyroid hormones, luteinizing hormone (LH), estradiol, progesterone and corticosterone of laying hens during a forced molt

1. Circulating concentrations of iodothyronines, luteinizing hormone(LH), estradiol(E2), progesterone and corticosterone were measured in hens before, during, and after a forced molt induced by fasting. 2. Corticosterone increased at the onset of molt, peaked at the maximal molt and returned to pre- and post-molt levels. LH, E2 and progesterone declined during the molt, and the decline was coincident with the cessation of egg production. 3. Thyroxine(T4), triiodothyronine (T3) and reverse triiodothyronine(rT3) increased during the molt. The increases of T4 and T3 were not abolished even if the forced molt was conducted in mild weather.     

New mutation affecting the synthesis of some membrane proteins and sporulation in Bacillus subtilis.

A new mutation, mpo, which affects the synthesis of some membrane proteins and sporulation in Bacillus subtilis was identified. The mpo mutation was tightly linked to the overproduction of membrane proteins MP32 and MP18 (molecular weights of 32,000 and 18,000, respectively) and the temperature-sensitive sporulation phenotype. Genetic analysis showed that the mpo mutation maps between the spoIIIB and lys loci.     

Analysis of water in Autonomous Biological Systems (ABS) samples.

Several soluble components, peptidase and amino acids, and carbon isotopic ratio in the water retrieved from flight experiments of Autonomous Biological Systems (ABS) as well as ground control samples are analyzed to interpret the condition, dynamics, material balance of the ABS ecosystems. Organic carbons in flight samples were found to be more abundant compared with the control ones, which suggested the uniform ecosystems in low gravity might easily dissolve more soluble components. The Mir-1997 flight sample showed higher C/N ratio probably because of the dissolution of carbon-rich plant materials.     

Vegetation mapping with the aid of low-altitude aerial photography

Abstract. A technique for fine-scale vegetation mapping with the aid of low-altitude aerial photography was developed. The procedure is as follows: 1. The site is divided into a lattice pattern - in case the site is too large to fit into a single photograph with satisfactory resolution. The coordinates of every lattice point are surveyed to be used as control points for geometric correction. A photograph of each block of the lattice is taken using a remote-controlled camera system lifted by a captive helium balloon. 2. The vegetation is classified on the basis of a phytosociological survey. 3. The shapes and locations of vegetation patches appearing in the photographs are entered into a computer, using a digitizer. A geometric correction is carried out through coordinate transformation referring to the coordinates of the control points and subsequently a draft vegetation map is produced. Finally, discrepancies are corrected and the map is coloured to produce the final version of the vegetation map. This technique was applied to vegetation mapping at a bar, 500 m wide and 2 km long, in the river Yoshino in Shikoku, Japan. A fine-scale vegetation map was obtained and used to analyse the influence of plants on geomorphic processes and community-specific hydrogeomorphic conditions on the bar.     

Apterichtus keramanus, a new snake-eel from Okinawa, southern Japan (Ophichthinae, Ophichthidae)

A new snake-eel,Apterichtus keramanus, is described on the basis of a single 276-mm TL specimen trawled from the coast of Kerama Islands, Okinawa Prefecture, Japan. The species is unique in the genus in having the posterior nostril opening entirely inside the mouth and a dark band running from the anteroventral margin of the eye to the upper lip.