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  • 1
    Electronic Resource
    Electronic Resource
    Synthesis of an iron(II)-braced proline-II tripod protein (1999)
    Springer
    International journal of peptide research and therapeutics 6 (1999), S. 33-43 
    Details
    ISSN: 1573-3904
    Keywords: 4-amino-l-proline ; circular dichroic spectropolarimeter ; proline-II helix ; protein engineering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This paper describes the engineering of braced tripod proteins for use as molecular frameworks. Specifically, a 30-residue tripod-shaped protein with three proline-II helical legs braced by an iron(II)tris(bipyridine) complex was modularly designed, chemically synthesized, and biophysically characterized. Three copies of a 10-residue leg peptide were covalently linked through sulfide bonds to an N-terminal apex (1,3,5-tris(methylene)benzene) and by amide bonds to the brace (FeII(Mbc)3: Mbc is 4′-methyl-2,2′-bipyridine-4-carbonyl). The leg peptide (H-Cys-Pro5-Pra(Mbc)-Pro3-NH2: Pra is cis-4-amino-l-proline) was assembled by the solid-phase method using Boc-Pra(Mbc)-OH, which was synthesized in 75% overall yield by coupling Mbc-OH to the 4-amino group of Boc-Pra-OCH3 and saponifying the methyl ester group.The iron(II)-braced tripod was assembled by S-alkylation of three copies of the leg peptide with 1,3,5-tris(bromomethyl)benzene followed by ligation of Fe2+ to the resulting unbraced tripod. The CD spectrum of the iron(II)-braced tripod showed a positive MLCT band at 570 nm and a negative π–π* band at 312 nm, so its FeII(Mbc)3 brace was predominantly in the Δ configuration. In a mostly acetonitrile solution at 25 °C, the leg peptide and the unbraced tripod isomerized from the proline-II helical form into the proline-I helical form but the iron(II)-braced tripod remained in the proline-II helical form.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008863326742
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  • 2
    Electronic Resource
    Electronic Resource
    Engineering of betabellin 15D: Copper(II)-induced folding of a fibrillar β-sandwich protein (1999)
    Springer
    International journal of peptide research and therapeutics 6 (1999), S. 3-14 
    Details
    ISSN: 1573-3904
    Keywords: β-sandwich ; de novo design ; protein engineering ; protein fibrils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The inverse protein-folding problem has been explored by designing de novo the betabellin target structure (a 64-residue β-sandwich protein), synthesizing a 32-residue peptide chain (HSLTAKIpkLTFSIAphTYTCAVpkYTAKVSH, wherep=DPro,k=DLys, andh=DHis) that might fold into this structure, and studying how its disulfide-bridged form (betabellin 15D) folds in 10 mM ammonium acetate with and without Cu2+. Circular dichroic spectropolarimetry indicated that at pH 5.8, 6.4, or 6.7 betabellin 15D exhibited β-sheet structure in the presence of Cu2+ but not in its absence. Electrospray mass spectrometry demonstrated that at pH 6.3 each molecule of betabellin 15D bound one or two Cu(II) ions. Electron microscopy showed that at pH 6.7 betabellin 15D formed short broad fibrils in the presence of Cu2+ but not in its absence. The observed width of the fibrils (7±2 nm) was consistent with the width (6.8nm) of a structural model of a fibril that contained two adjacent rows of betabellin 15D β-sandwiches joined lengthwise by multiple intersheet hydrogen bonds and widthwise by multiple Cu(II)-imidazole bonds. Electron paramagnetic resonance spectrometry revealed that some pairs of Cu(II) ions in a Cu(II)/betabellin 15D complex were magnetically coupled, which is consistent with the structural model of the Cu(II)/betabellin 15D fibril.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02443613
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  • 3
    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
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  • 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: 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
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesis of an iron(II)-braced proline-II tripod protein (1999)
    Springer
    International journal of peptide research and therapeutics 6 (1999), S. 33-43 
    Details
    ISSN: 1573-3904
    Keywords: 4-amino-l-proline ; circular dichroic spectropolarimetry ; proline-II helix ; protein engineering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This paper describes the engineering of braced tripod proteins for use as molecular frameworks. Specifically, a 30-residue tripod-shaped protein with three proline-II helical legs braced by an iron(II)tris(bipyridine) complex was modularly designed, chemically synthesized, and biophysically characterized. Three copies of a 10-residue leg peptide were covalently linked through sulfide bonds to an N-terminal apex (1,3,5-tris(methylene)benzene) and by amide bonds to the brace (FeII (Mbc)3: Mbc is 4′-methyl-2,2′-bipyridine-4-carbonyl). The leg peptide (H-Cys-Pro5-Pra(Mbc)-Pro3-NH2: Pra iscis-4-amino-l-proline) was assembled by the solid-phase method using Boc-Pra(Mbc)-OH, which was synthesized in 75% overall yield by coupling Mbc-OH to the 4-amino group of Boc-Pra-OCH3 and saponifying the methyl ester group. The iron(II)-braced tripod was assembled by S-alkylation of three copies of the leg peptide with 1,3,5-tris(bromomethyl)benzene followed by ligation of Fe2+ to the resulting unbraced tripod. The CD spectrum of the iron(II)-braced tripod showed a positive MLCT band at 570 nm and a negative π-π* band at 312 nm, so its FeII(Mbc)3 brace was predominantly in the Δ configuration. In a mostly acetonitrile solution at 25°C, the leg peptide and the unbraced tripod isomerized from the proline-II helical form into the proline-I helical form but the iron(II)-braced tripod remained in the proline-II helical form.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02443616
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  • 6
    Electronic Resource
    Electronic Resource
    Engineering of betabellin 15D: Copper(II)-induced folding of a fibrillar β-sandwich protein (1999)
    Springer
    International journal of peptide research and therapeutics 6 (1999), S. 3-14 
    Details
    ISSN: 1573-3904
    Keywords: β-sandwich ; de novo design ; protein engineering ; protein fibrils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The inverse protein-folding problem has been explored by designing de novo the betabellin target structure (a 64-residue β-sandwich protein), synthesizing a 32-residue peptide chain (HSLTAKIpkLTFSIAphTYTCAVpkYTAKVSH, where p = DPro, k = DLys, and h = DHis) that might fold into this structure, and studying how its disulfide-bridged form (betabellin 15D) folds in 10 mM ammonium acetate with and without Cu2+. Circular dichroic spectropolarimetry indicated that at pH 5.8, 6.4, or 6.7 betabellin 15D exhibited β-sheet structure in the presence of Cu2+ but not in its absence. Electrospray mass spectrometry demonstrated that at pH 6.3 each molecule of betabellin 15D bound one or two Cu(II) ions. Electron microscopy showed that at pH 6.7 betabellin 15D formed short broad fibrils in the presence of Cu2+ but not in its absence. The observed width of the fibrils (7 ± 2 nm) was consistent with the width (6.8 nm) of a structural model of a fibril that contained two adjacent rows of betabellin 15D β-sandwiches joined lengthwise by multiple intersheet hydrogen bonds and widthwise by multiple Cu(II)-imidazole bonds. Electron paramagnetic resonance spectrometry revealed that some pairs of Cu(II) ions in a Cu(II)/betabellin 15D complex were magnetically coupled, which is consistent with the structural model of the Cu(II)/betabellin 15D fibril.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008878308995
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