Increased xylitol production rate during long-term cell recycle fermentation of Candida tropicalis

Long-term cell recycle fermentations of Candida tropicalis were performed over 14 rounds of fermentation. The average xylitol concentrations, fermentation times, volumetric productivities and product yields for 14 rounds were 105 g l^–1, 333 h, 4.4 g l^–1 h^–1 and 78%, respectively, in complex medium; and 110 g l^–1, 284 h, 5.4 g l^–1 h^–1 and 81%, respectively, in a chemically defined medium. These productivities were 1.7 and 2.4 times those with batch fermentation in the complex and chemically defined media, respectively. The xylitol yield from xylose with cell recycle fermentation using the chemically defined medium was 81% (w/w), which was 7% greater than the xylitol yield with batch fermentation (74%); both modes of fermentation gave the same yield using the complex medium. These results suggest that the chemically defined medium is more suitable for production of xylitol than complex medium.     

Surface plasmon resonance immunosensor using self-assembled protein G for the detection of Salmonella paratyphi

A surface plasmon resonance (SPR) based immunosensor using self-assembled protein G was developed for the detection of Salmonella paratyphi. In order to endow a solid substrate binding affinity to protein G, the free amine (-NH2) of protein G was substituted into thiol (-SH) using 2-iminothiolane. Thus, self-assembled protein G was fabricated on gold (Au) substrate. The formation of protein G layer on Au surface, and the binding of antibody and antigen in series were confirmed by SPR spectroscopy. The surface morphology analysis of the protein G layer on Au surface was performed by atomic force microscope (AFM). Consequently, an immunosensor based on SPR for the detection of S. paratyphi using self-assembled protein G was developed with a detection range of 10(2)-10(7) CFU/ml. The current fabrication technique of a SPR immunosensor for the detection of S. paratyphi could be applied to construct other immnosensors or protein chips.     

N-4-methansulfonamidobenzyl-N'-2-substituted-4-tert-butyl-benzyl thioureas as potent vanilloid receptor antagonistic ligands

A series of N-4-methansulfonamidobenzyl-N'-2-substituted-4-tert-butylbenzyl thioureas were prepared for the study of their agonistic/antagonistic activities to the vanilloid receptor in rat DRG neurons. Their structure-activity relationship reveals that there is a space for another hydrophobic binding interaction around 2-position in 4-tert-butylbenzyl region. Among the prepared derivatives, 6n show the highest antagonistic activity against the vanilloid receptor (IC(50)=15 nM).     

N-4-Substituted-benzyl-N'-tert-butylbenzyl thioureas as vanilloid receptor ligands: investigation on the role of methanesulfonamido group in antagonistic activity

A series of N-4-substituted-benzyl-N'-tert-butylbenzyl thioureas were prepared for the study of their agonistic/antagonistic activities to the vanilloid receptor in rat DRG neurons. Their structure-activity relationship reveals that not only the two oxygens and amide hydrogen of sulfonamido group, but also the optimal size of methyl in methanesulfonamido group play an integral role for the antagonistic activity on vanilloid receptor.     

Structure-based virtual screening and biological evaluation of potent and selective ADAM12 inhibitors

We describe a series of potent and selective inhibitors of ADAM12 that were discovered using computational screening of a focused virtual library. The initial structure-based virtual screening selected 64 compounds from a 3D database of 67,062 molecules. Being evaluated by a cell-based ADAM12 activity assay, compounds 5, 11, 14, 16 were further identified as the potent and selective inhibitors of ADAM12 with low nanomolar IC₅₀ values. The mechanism underlying the potency and selectivity of a representative compound, 5, was investigated through molecular docking studies.     

Structural mechanism for inactivation and activation of CAD/DFF40 in the apoptotic pathway

CAD/DFF40 is responsible for the degradation of chromosomal DNA into nucleosomal fragments and subsequent chromatin condensation during apoptosis. It exists as an inactive complex with its inhibitor ICAD/DFF45 in proliferating cells but becomes activated upon cleavage of ICAD/DFF45 into three domains by caspases in dying cells. The molecular mechanism underlying the control and activation of CAD/DFF40 was unknown. Here, the crystal structure of activated CAD/DFF40 reveals that it is a pair of molecular scissors with a deep active-site crevice that appears ideal for distinguishing internucleosomal DNA from nucleosomal DNA. Ensuing studies show that ICAD/DFF45 sequesters the nonfunctional CAD/DFF40 monomer and is also able to disassemble the functional CAD/DFF40 dimer. This capacity requires the involvement of the middle domain of ICAD/DFF45, which by itself cannot remain bound to CAD/DFF40 due to low binding affinity for the enzyme. Thus, the consequence of the caspase-cleavage of ICAD/DFF45 is a self-assembly of CAD/DFF40 into the active dimer.     

Isolation and characterization of a root nodule-specific cysteine proteinase cDNA from soybean

We have determined that a nodule-specific cDNA clone (GmCysP1), obtained from a soybean root nodule-specific EST pool, encodes cysteine proteinase. Its amino acid sequence homology, as well as the conservation of typical motifs and amino acid residues involved in active site formation, shows that GmCysP1 can be classified as a legumain (C13) family cysteine proteinase, belonging to clan CD. Moreover, based on its expression patterns,GmCysP1 is a nodule-specific cysteine proteinase gene that is possibly associated with nodule development or senescence. Our genomic Southern analysis also suggests thatGmCysP1 is a member of a multigene family. Therefore, we propose that GmCysP1 is the first to be identified as a nodule-specific and senescence-related cysteine proteinase that belongs to the legumain family from soybean.     

Distribution of lichen flora on South Korea

After an overview on the temporary situation of the lichenology in South Korea, localities of 95 macrolichen taxa are reported for South Korea. In this revised lichen flora of South Korea, 16 species are apparently new to the territory. Voucher specimens have been deposited in the Korean Lichen Research Institute (KoLRI) at Sunchon National University in Korea, and duplicates have also been donated to the National History Museum and Institute, in Chiba, (CBM) Japan.