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  • 1
    Electronic Resource
    Electronic Resource
    Kinetics of isomerization for the proline helical forms of two oligoproline redox arrays by circular dichroic spectropolarimetry (1999)
    Springer
    International journal of peptide research and therapeutics 6 (1999), S. 61-69 
    Details
    ISSN: 1573-3904
    Keywords: biexponential kinetics ; proline helices ; substituted proline residues
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of isomerization of the helical forms of three oligoprolines was determined by far-ultraviolet CD spectropolarimetry and kinetic analysis by singular value decomposition. ZRA (Pro3-X-Pro2-Y-Pro2-Z-Pro3) and ZRA2 (Pro7-X-Pro2-Y-Pro2-Z-Pro7) bear large redox-active substituents on proline residues X, Y, and Z, but P9 (Pro9) does not. All three peptides formed a stable proline-II helix in water. In acetonitrile, both ZRA2 and P9 were converted into a proline-I helical form but ZRA remained predominantly in the proline-II helical form. Evidently, in order to undergo substantial proline II→I isomerization, an oligoproline chain containing large substituents needs to have a segment of consecutive unsubstituted proline residues that is sufficiently long to form a stable proline helix. Biexponential kinetics (A→B, k1 = ∼3.3 × 10-4 s-1; B→C, k2 = ∼0.8 × 10-4 s-1) were observed for the proline II→I isomerization of ZRA2 and P9 in acetonitrile and for the proline I→II isomerization of ZRA2 in water, which provides evidence for the growth and decay of a major kinetic intermediate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008819511721
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Engineering of deltoid and reduced deltoid: Two chimeric proteins containing the oligomerization site of the hepatitis delta antigen (1999)
    Springer
    International journal of peptide research and therapeutics 6 (1999), S. 23-32 
    Details
    ISSN: 1573-3904
    Keywords: antiparallel coiled coil ; deltoid ; hepatitis delta antigen ; molecular modeling ; oligomerization site ; protein engineering ; quadrin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Hepatitis delta antigen (HDAg) must form oligomers to be biologically active. Quadrin (HDAg-(12–60)-Tyr) is a 50-residue protein segment from the oligomerization domain of HDAg. The crystal structure of quadrin shows an octamer consisting of four identical copies of a dimer containing an antiparallel α-helical coiled coil. Each end of the dimer contains an oligomerization site that interacts isologously with the oligomerization site of another dimer to form a right-angled corner. The resulting quadrin octamer is a 400-residue square protein surrounding a large aqueous hole. We have designed, chemically synthesized, and characterized deltoid and reduced deltoid, two 51-residue chimeric proteins that structurally and functionally mimic one of the two oligomerization sites of the quadrin dimer. Dimerization of deltoid or reduced deltoid should emulate the dimerization of two quadrin dimers to form one right-angled corner of the square. Deltoid and reduced deltoid were designed by molecular modeling, mechanics, and dynamics and synthesized by the solid-phase method. The amino acid sequence of deltoid (GREDILEQWVSCRKKL + PKAPPEE + LRKLKKKCKKLEEDNPWLGNIKGIIGKY) is a chimera of three protein segments: HDAg-(12–28), Thermus thermophilus serine tRNA synthase-(59–65), and HDAg-(34–60)-Tyr. Cysteine (C) was introduced at two positions to explore the effects of the presence (deltoid) or absence (reduced deltoid) of an interhelical disulfide bond. Circular dichroic spectropolarimetry revealed that both synthetic proteins form an α-helical structure that is stable over a wide range of pH and KCl concentrations. Size-exclusion chromatography indicated that deltoid and reduced deltoid each form a dimer. Interconversion of these monomers and dimers should be useful model systems for studying the structural features of the right-angled corners of the quadrin octamer that contribute to HDAg oligomerization. If, like quadrin, deltoid or reduced deltoid interferes with HDAg oligomerization, it might serve as a lead compound for the design of potent HDV inhibitors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008811309904
    Location Call Number Limitation Availability
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Kinetics of isomerization for the proline helical forms of two oligoproline redox arrays by circular dichroic spectropolarimetry (1999)
    Springer
    International journal of peptide research and therapeutics 6 (1999), S. 61-69 
    Details
    ISSN: 1573-3904
    Keywords: biexponential kinetics ; proline helices ; substituted proline residues
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The kinetics of isomerization of the helical forms of three oligoprolines was determined by far-ultraviolet CD spectropolarimetry and kinetic analysis by singular value decomposition. ZRA (Pro3-X-Pro2-Y-Pro2-Z-Pro3) and ZRA2 (Pro7-X-Pro2-Y-Pro2-Z-Pro7) bear large redox-active substituents on proline residues X, Y, and Z, but P9 (Pro9) does not. All three peptides formed a stable proline-II helix in water. In acetonitrile, both ZRA2 and P9 were converted into a proline-I helical form but ZRA remained predominantly in the proline-II helical form. Evidently, in order to undergo substantial proline II→I isomerization, an oligoproline chain containing large substituents needs to have a segment of consecutive unsubstituted proline residues that is sufficiently long to form a stable proline helix. Biexponential kinetics (A→B, k1=∼3.3×10−4s−1; B→C, k2=∼0.8×10−4s−1) were observed for the proline II→I isomerization of ZRA2 and P9 in acetonitrile and for the proline I→II isomerization of ZRA2 in water, which provides evidence for the growth and decay of a major kinetic intermediate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02443619
    Location Call Number Limitation Availability
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    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Engineering of deltoid and reduced deltoid: Two chimeric proteins containing the oligomerization site of the hepatitis delta antigen (1999)
    Springer
    International journal of peptide research and therapeutics 6 (1999), S. 23-32 
    Details
    ISSN: 1573-3904
    Keywords: antiparallel coiled coil ; deltoid ; hepatitis delta antigen ; molecular modeling ; oligomerization site ; protein engineering ; quadrin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Hepatitis delta antigen (HDAg) must form oligomers to be biologically active. Quandrin (HDAg-(12–60)-Tyr) is a 50-residue protein segment from the oligomerization domain of HDAg. The crystal structure of quadrin shows an octamer consisting of four identical copies of a dimer containing an antiparallel α-helical coiled coil. Each end of the dimer contains an oligomerization site that interacts isologously with the oligomerization site of another dimer to form a right-angled corner. The resulting quadrin octamer is a 400-residue square protein surrounding a large aqueous hole. We have designed, chemically synthesized, and characterized deltoid and reduced deltoid, two 51-residue chimeric proteins that structurally and functionally mimic one of the two oligomerization sites of the quadrin dimer. Dimerization of deltoid or reduced deltoid should emulate the dimerization of two quadrin dimers to form one right-angled corner of the square. Deltoid and reduced deltoid were designed by molecular modeling, mechanics, and dynamics and synthesized by the solid-phase method. The amino acid sequence of deltoid (GREDILEQWVSCRKKL+PKAPPEE+LRKLKKKCKKLEEDNPWLGNIKGIIGKY) is a chimera of three protein segments: HDAg-(12–28),Thermus thermophilus serine tRNA synthase-(59–65), and HDAg-(34–60)-Tyr. Cysteine (C) was introduced at two positions to explore the effects of the presence (deltoid) or absence (reduced deltoid) of an interhelical disulfide bond. Circular dichroic spectropolarimetry revealed that both synthetic proteins from an α-helical structure that is stable over a wide range of pH and KCl concentrations. Size-exclusion chromatography indicated that deltoid and reduced deltoid each form a dimer. Interconversion of these monomers and dimers should be useful model systems for studying the structural features of the right-angled corners of the quandrin octamer that contribute to HDAg oligomerization. If, like quadrin, deltoid or reduced deltoid interferes with HDAg oligomerization, it might serve as a lead compound for the design of potent HDV inhibitors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02443615
    Location Call Number Limitation Availability
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    Paper (German National Licenses)
    Fulltext
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