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  • 1
    ISSN: 1573-3904
    Keywords: Conotoxin GS ; γ-Carboxyglutamic acid ; Solution synthesis ; Disulfide structure ; Disulfide isomer ; CD spectrum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Conotoxin GS, a γ-carboxyglutamic acid(Gla)-containing neurotoxic peptide composed of 34 amino acid residues with one Gla residue and three intramolecular disulfide bonds, was synthesized in solution by the Boc strategy, using the cyclohexyl group to protect the γ,γ-dicarboxyl functional side chain of the Gla residue. All of the protecting groups were removed by the HF procedure. During the synthesis, the Gla residue was completely stable and decarboxylated product was observed. The free peptide was subjected to the oxidative folding reaction. The reaction proceeded almost quantitatively in the presence of reduced and oxidized glutathione; however, no product was formed in the absence of redox reagents concomitant with the formation of disulfide isomers or intermediates. The final product was confirmed to be identical to natural conotoxin GS on reversed phase- and ion exchange-HPLC as well as capillary zone electrophoresis. The disulfide structure of synthetic conotoxin GS was determined by gas-phase sequencing and mass spectrometry of its proteolytic fragments and was found to be identical to those of other ω-conotoxins. The major disulfide isomer obtained during the oxidative folding reaction without redox reagents was determined in the same manner. To clarify the role of the Gla residue and the disulfide structure in the conotoxin GS molecule, decarboxylated conotoxin GS and its disulfide isomer were also synthesized, and the neurotoxic activities and circular dichroism spectra of these peptides were compared with those of conotoxin GS and its disulfide isomer. The results showed that the correct disulfide structure was necessary for expression of the toxicity; however, the presence of the Gla residue was not a prerequisite for both the activity and the calcium-dependent conformational transition.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1075-2617
    Keywords: Solution synthesis ; human midkine ; powerful solvent system ; powerful solvent system ; active region ; Chemistry ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Human midkine (hMK), a novel heparin-binding neurotrophic factor consisting of 121 amino acid residues with five intramolecular disulphide bonds, was synthesized by solution procedure in order to demonstrate the usefulness of our newly developed solvent system, a mixture of dichloromethane or chloroform and trifluoroethanol. The final protected 121-residue peptide was assembled from two large fully protected intermediates, Boc-(1-5 9)-OH and H-(60-121)-OBzl, in CHL/TFE (3:1, v/v) using water-soluble carbodiimide in the presence of HOOBt as coupling reagents. After removal of the protecting groups by HF followed by treatment with Hg(OAc)2 in 50% acetic acid, the fully deprotected peptide was subjected to the oxidative folding reaction. The final product was confirmed to have the correct disulphide structure from its tryptic peptide mapping and to possess the same biological activities as those of the natural product. In order to clarify the active region of the hMK molecule, the N-terminal and C-terminal half domains [(1-59) and (60-121)] were also synthesized by the same procedure used for the hMK synthesis. The C-half domain was confirmed to show the full pattern of bioactivities except for the neuronal cell survival activity, while the N-half one showed much less activity in general.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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