Rapid and Efficient Purification of Haemolymph Ferritin from Cricket, Gryllus bimaculatus

The Gryllus bimaculatus ferritin was purified from the haemolymph by a consecutive four‐step procedures consisting of 50% ammonium sulfate fractionation, anion exchange column chromatography using HiTrap^TM Q column (1.6 x 4 cm, Amersham Bioscience), 70°C heat treatment for 10 min, acid treatment of 0.1 M sodium acetate buffer (pH 6.0), and gel filtration column chromatography using G4000SW column (0.75 x 60 cm, Tosoh, Japan) connected on FPLC system. The purified ferritin was found to have two major subunits of 32 and 30 kDa and three minor subunits of 28, 27, and 25 kDa by 2D electrophoresis analysis. Amino acid composition analysis showed that there are high contents of Asp, Glu, Met, Leu, and Lys residues in ferritin while low contents of Cys, Tyr, and Trp residues in the protein. G. bimaculatus haemolymph ferritin could be classified as a methionine‐rich protein.     

EFFECT OF MEAT APPEARANCE ON SOUTH KOREAN CONSUMERS' CHOICE OF PORK CHOPS DETERMINED BY IMAGE METHODOLOGY

The effect of appearance characteristics of fresh pork on Korean consumers' preferences was assessed using images of pork chops. Consumers (1015) in six provinces selected their preferred chop from 16 images modified systematically to give two levels each of fat cover, color, marbling and drip. Meat color was the most important characteristic; similar numbers of consumers chose the dark and light red meat colored pork. Almost two‐thirds of the consumers chose consistently the option without drip. A strong characteristic was that almost half of the Korean consumers chose the marbled pork, although fat cover was not an important selection criterion. Similar preferences were observed on a regional basis, except for color, which varied according to region. More female, particularly the married ones, than male consumers preferred the light red, no drip and marbled options.     

Taxonomic review of the genus Copelatus Erichson (Coleoptera: Dytiscidae) in Korea

A taxonomic review of the genus Copelatus Erichson (Coleoptera: Dytiscidae) in Korea is presented. In the present study, five species of Copelatus are recognized from Korea, including one unrecorded species, C. kammuriensis. We provide a key to the Korean species of Copelatus, diagnosis of one unrecorded species, habitus photographs, scanning electron micrographs of the elytron, and illustrations of the aedeagus.     

Biomass,production and nutrient distribution of a natural oak forest in central Korea

Biomass, production, and nutrient distribution of a pure Quercus variabilis Bl. stand (stand 1) and two mixed Q. variabilis–Q. mongolica Fisch. stands (stand 2 and 3) were investigated in central Korea. Stand 1 naturally occurred on a site with a southern aspect while stand 2 and stand 3 occurred on sites with a northern aspect. Total (overstory+understory vegetation) biomass (tha^-1) and annual production (tha^–1year^–1) were 137.8 and 11.1 for stand 1, 216.2 and 16.6 for stand 2, and 253.3 and 19.7 for stand 3. Nutrient contents (kgha^–1) in the vegetation were distributed as follows: K, 478–860; N, 471–839; Ca, 428–791; Mg, 72–125; Na, 77–141; and P, 37–71, and were greatest in stand 3 followed by stand 2, and stand 1. Stand density influenced the differences in biomass, annual production and nutrient contents in the vegetation. Forest floor dry mass and N content (kgha^–1) were 13400 and 169 for stand 1, 10400 and 133 for stand 2, and 11200 and 127 for stand 3. Total amounts of N, P and Na in the ecosystem were greatest in the upper 40cm of mineral soil followed by the vegetation and forest floor. However, the vegetation contained a greater amount of K than the mineral soil. It appeared that microenvironments, such as, aspect influenced the distribution of natural oak species within a relatively small area and resulted in differences in biomass, production and nutrient distribution among the stands.     

Biocatalytic properties and substrate-binding ability of a modular GH10 β-1,4-xylanase from an insect-symbiotic bacterium,Streptomyces mexicanus HY-14

The gene (1350-bp) encoding a modular β-1,4-xylanase (XylU), which consists of an N-terminal catalytic GH10 domain and a C-terminal carbohydrate-binding module 2 (CBM 2), from Streptomyces mexicanus HY-14 was cloned and functionally characterized. The purified His-tagged recombinant enzyme (rXylU, 44.0 kDa) was capable of efficiently hydrolyze diverse xylosidic compounds, p-nitrophenyl-cellobioside, and p-nitrophenyl-xylopyranoside when incubated at pH 5.5 and 65°C. Especially, the specific activities (649.8 U/mg and 587.0 U/mg, respectively) of rXylU toward oat spelts xylan and beechwood xylan were relatively higher than those (<500.0 U/mg) of many other GH10 homologs toward the same substrates. The results of enzymatic degradation of birchwood xylan and xylooligosaccharides (xylotriose to xylohexaose) revealed that rXylU preferentially hydrolyzed the substrates to xylobiose (>75%) as the primary degradation product. Moreover, a small amount (4%<) of xylose was detected as the degradation product of the evaluated xylosidic substrates, indicating that rXylU was a peculiar GH10 β-1,4-xylanase with substrate specificity, which was different from its retaining homologs. A significant reduction of the binding ability of rXylU caused by deletion of the C-terminal CBM 2 to various insoluble substrates strongly suggested that the additional domain might considerably contribute to the enzyme-substrate interaction.