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      • A support system for disaster relief activities at petrochemical complexes

        Yasuhiro Kajihara,Seiko Taki 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8

        An assistance system has been developed for supporting emergency activities in deserter prevention. Two key functions were regarded specially to design the assistance system, which is a function to provide interactive communication between a general headquarters and on-site operators and a function to provide instructions. The interactive communication between both terminals is carried out in voice, moving images, freeze-frame pictures and text. The assistance system on the side of on-site operators is designed compact and lightweight so that an operator wears it quite handily. Additionally, the assistance system on the side of the general headquarters makes available a function to transform conversation in text automatically. The background of this research, process of operational test of the assistance system for last four years and results are shown in this paper.

      • Synthetic Study of Carbohydrate Binding Domain of Siglec7

        Akihisa Otsuki,Ryo Okamoto,Masayuki Izumi,Yasuhiro Kajihara 한국당과학회 2012 한국당과학회 학술대회 Vol.2012 No.1

        Sialic acid-binding immunoglobulin-like lectin (Siglec) 7 is one of the sialic acid binding protein that plays an important role in immune system. Siglec 7 is expressed on natural killer cells and displays a unique ligand binding properties comparing to the other members of the Siglec family, specifically binds to  2,8-disialyl residues. The precise structural analysis of Siglec 7 has been already performed, and amino acid residues involved in the ligand binding are reported. In such context, we set out the first total chemical synthesis of Siglec 7 carbohydrate binding domain (CBD) which consists of 127 amino acid residues. Since chemical synthesis can easily introduce unnatural amino acids, we envisioned that we could produce an artificial sialic acid binding lectin based on this chemical synthetic strategy. The synthesis of Siglec 7 CBD was carried out by convergent total chemical synthesis. The whole polypeptide was assembled from 5 peptide segments (Figure), which were synthesized by conventional solid phase peptide synthesis. We applied native chemical ligation (NCL) for the coupling of these segments sequentially from C-terminus, combined with alkylation with haloacetoamide or desulfuration reaction. These reactions can provide pseudo-Gln residue or Ala residue from Cys residues at the ligation sites. Based on these strategies we have successfully obtained the full-length polypeptide of Siglec 7 CBD and currently are investigating the in vitro folding step.

      • Chemical Approach for the Synthesis of Homogeneous Large Glycoproteins

        Shohei Imada,Ryo Okamoto,Masayuki Izumi,Yasuhiro Kajihara 한국당과학회 2012 한국당과학회 학술대회 Vol.2012 No.1

        Glycoprotiens are responsible in many biological events. However oligosaccharides covalently attached to these proteins always exhibit heterogeneity. This has been a hindrance to investigate what oligosaccharide structure is essential for the individual biological event. Therefore we have examined the chemical synthesis of several glycoproteins such as cytokines consist of 70 to 166 amino acid residues. [1-3] However, glycoproteins used in the cell-cell communication or immune response exhibit larger molecular weight comparing with those of cytokines we have synthesized. Unfortunately, the synthesis of such large and homogeneous glycoproteins is still far from our current achievements, because we have not established an efficient method for the synthesis of large glycoproteins yet. Native chemical ligation[4] is a powerful method to couple two polypeptide chains through a native amide bond. This ligation takes place between peptide-C-terminal thioester and cysteine at the N-terminal of another peptide. Using this ligation between glycopeptide-thioester synthesized by chemical method and long peptide prepared from E. coli expression, we have examined the synthesis of large glycoprotein. In this presentation, we would discuss the first synthesis of large and homogeneous glycosylpolypeptide chain (25 kDa) consists of over 200 amino acid residues.

      • Chemical Synthesis of Intentionally Misfolded Homogeneous Glycoprotein: A Unique Approach for the Study of Glycoprotein Quality Control

        Masayuki Izumi,Yutaka Makimura,Simone Dedola,Akira Seko,Akiko Kanamori,Masafumi Sakono,Yukishige Ito,Yasuhiro Kajihara 한국당과학회 2012 한국당과학회 학술대회 Vol.2012 No.1

        Biosynthesis of glycoproteins in the endoplasmic reticulum employs a quality control (QC) system, which discriminates and excludes misfolded malfunctional glycoproteins from correctly folded one. In the QC system, UDP-glucose:glycoprotein glucosyltransferase (UGGT) recognizes misfolded glycoprotein bearing high-mannose type N-glycan and glucosylate it so that the misfolded proteins can interact with molecular chaperones calnexin/calreticulin to attain correctly folded structure. As chemical tools to study glycoprotein quality control system at molecular level, we systematically synthesized misfolded homogeneous glycoproteins bearing high-mannose type oligosaccharide. Interleukin 8 (IL-8) is a nonglycosylated protein consisted of 72 amino acid residues and two disulfide bonds between Cys7–Cys34 and Cys9–Cys50. As a model, we incorporated high-mannose type (Man9GlcNAc2) oligosaccharide at the Asn36. The full-length glycosylpolypeptide chain was successfully synthesized by native chemical ligation between N-terminal 33-amino acid peptide-thioester and C-terminal 39-amino acid glycopeptide, which was prepared with Fmoc-Asn derivative having high-mannose oligosaccharide on the side chain.Extensive folding experiments of chemically synthesized homogeneous IL-8 glycopeptide yielded correctly folded glycoprotein with native disulfide bond patterns as well as misfolded glycoproteins with non-native disulfide bond patterns and a disulfide bond-linked misfolded homodimer. Other misfolded glycoprotein models with one and no disulfide bond and glycopeptides consisted of C-terminal 39-amino acid residues were also prepared. Transfer of glucose residue to these homogeneous glycoprotein analogues by UGGT was analyzed by using LC-MS. This assay proved that the critical endoplasmic reticulum folding sensor enzyme, UGGT recognizes misfolded glycosyl-IL-8s with different preferences. The most favored substrate was a homodimer which exhibits molten globule-like hydrophobic nature, and the least favored substrate was a correctly folded glycosyl-IL-8. Glycoproteins and glycopeptides having non-native disulfide bonds were also favored substrates.

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