Studies on AI-77s,microbial products with gastroprotective activity. Structures and the chemical nature of AI-77s

The structures and the chemical nature of a novel gastroprotective substance AI-77-B (1) and its analogues AI-77-C (2), D (3), F (4) and G (5), which are produced by Bacillus pumilus AI-77, are described. The structure of 1 was confirmed to be 6-[[1(S)-(3(S), 4-dihydro-8-hydroxy-1-oxo-1H-2-benzopyran-3-yl)-3-methylbutyl]amino]-4(S),5(S)-dihydroxy-6-oxo-3(S)-aminohexanoic acid by X-ray in combination with chemical studies and the structures of 2, 3, 4 and 5 were determined by chemical syntheses from 1 and spectral analyses.     

Impact tensile fracture testing of a brittle polymer

The fracture behavior of a brittle polymer, methylmethacrylate–butadiene–styrene resin, under impact tensile loading was studied using single-edge-cracked specimens. The dynamic load and displacement were measured with a Piezo sensor and a high-speed extensometer, respectively. The load and displacement diagram, i.e., the external work, U_ex, applied to the specimen was used to determine the elastic energy, E_e, and non-elastic energy, E_n, due to viscoelastic and plastic deformation, and the fracture energy, E_f, for creating new fracture surface, A_s. The energy-release rates were then estimated using G_t=U_ex/A_s and G_f=E_f/A_s. The values of G_t and G_f were correlated with the fracture loads and the mean crack velocities determined from the load and time relationships.     

Flocculation of diatomite by methylated milk casein in seawater

A new biodegradable flocculant was prepared from a common and inexpensive protein. Milk casein was methylated in a 0.05 M HCl methyl alcohol solution at room temperature. The methylated milk casein (MeCS), having a methylation degree of 81%, was applied to the separation or flocculation of diatomite in seawater (pH 8.1+/-0.1) at room temperature (18-23 degrees C). The flocculating ability of MeCS was evaluated by a sedimentation balance method (cumulative measurement method). The diatomite suspension was effectively flocculated by the addition of a small amount of MeCS (0.25 wt% of the diatomite weight). The results of sedimentation analysis showed that the size-frequency curve had a very sharp and high peak; thus the diatomite floc formed by MeCS had a rather uniform size. The settling velocity of diatomite floc at the appropriate MeCS dosages (0.25-2 wt% of diatomite) was about 3 x 10(-3) ms(-1).     

Novel bisabolene-type sesquiterpenoids with a conjugated diene isolated from the okinawan sea sponge theonella cf. swinhoei

Three Novel sesquiterpenoids have been isolated from the Okinawan see sponge $\text{Theonella}$ cf. $\text{swinhoei}$ and the structures have been determined on the basis of the spectral data and chemical reactions.     

Highly active alumina for aldol condensation of acetone

Eleven kinds of aluminas were prepared from various starting materials by different methods. An alumina prepared from sodium aluminate by precipitation with carbon dioxide was found to exhibit an extraordinarily high catalytic activity for aldol condensation of acetone at 0 °C.

---

. , , 0°C.

     

Spectrophotometric determination of carp vitellogenin using a sequential injection analysis technique equipped with a jet ring cell

A sequential injection analysis (SIA) technique, in which antibody-immobilized microbeads were transferred to a jet ring (JR) cell, was used in determination of carp vitellogenin (Vg). The determination is based on a sandwich immunoassay in which two types of reactions between anti carp Vg antibodies and carp Vg are used. Namely, the antibody for the first reaction step was immobilized on microbeads (Sephadex beads), and an antibody labeled with a horseradish peroxidase (HRP) was used in the second step of the reaction. A mixed solution of hydrogen peroxide and o-phenylenediamine (OPD) was used as the source of the chromophore in the reaction. The microbeads-immobilized antibody, Vg analyte, HRP-labeled anitbody and the color developing solution were introduced automatically into the JR cell of the SIA system in a programmed sequence, and the absorbance of the oxidized OPD product was used to determine the amount of Vg present. The optimal incubation times for the immuno-raction for the first and the second steps were determined at 120 and 60 min, respectively, taking into account the sensitivity to the Vg determination. Under these conditions, a good linear correlation was obtained between Vg concentration and the absorbance of the oxidized OPD. The lower detection limit for the determination of Vg was about 5 ng ml⁻¹ in this system. The method developed here represents a simple, accurate method for the determination method of Vg.     

Nepenthesin, a unique member of a novel subfamily of aspartic proteinases: enzymatic and structural characteristics

Carnivorous plants are known to secrete acid proteinases to digest prey, mainly insects, for nitrogen uptake. In our recent study, we have purified, for the first time, to homogeneity two acid proteinases, nepenthesin I (Nep I) and nepenthesin II (Nep II) from the pitcher fluid of Nepenthes distillatoria and investigated their enzymatic and structural characteristics. Both enzymes were optimally active at pH approx. 2.6 toward acid-denatured hemoglobin; the specificity of Nep I toward oxidized insulin B chain appears to be similar, but slightly wider than those of other aspartic proteinases (APs). At or below 50 degrees C both enzymes were remarkably stable; especially Nep I was extremely stable over a wide range of pH from 3 to 10 for over 30 days. This suggests an evolutionary adaptation of the enzymes to their specific habitat. We have also cloned the cDNAs and deduced the complete amino acid sequences of the precursors of Nep I and Nep II from the pitcher tissue of Nepenthes gracilis. Although the corresponding mature enzymes are homologous with ordinary pepsin-type APs, both enzymes had a high content of cysteine residues (12 residues per molecule), which are assumed to form six unique disulfide bonds as suggested by computer modeling and are thought to contribute toward the remarkable stability of Neps. Moreover, the amino acid sequence identity of Neps with ordinary APs, including plant vacuolar APs, are remarkably low (approx. 20%), and phylogenetic comparison shows that Neps are distantly related to them to form a novel subfamily of APs with a high content of cysteine residues and a characteristic insertion, named 'the Nep-type AP (NAP)-specific insertion', including a large number of novel, orthologous plant APs emerging in the gene/protein databases.