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  • Analytical Chemistry and Spectroscopy  (3)
  • proline-II helix  (2)
  • 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 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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    Paper (German National Licenses)
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  • 2
    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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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Differentiation between selected pairs of tripeptide diastereomers by tandem mass spectrometry on a hybrid tandem mass spectrometer (1993)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 7 (1993), S. 339-342 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Low-energy collisionally activated decomposition (CAD) and unimolecular decomposition of the [M + H]+ ions for X-L-Pro-L-Phe, where X is L-Ala, D-Ala, L-Asp, or D-Asp, allow easy differentiation between the LLL and DLL diastereomers. Tandem mass spectrometric (MS/MS) studies of the [M + H]+ ions formed by fast-atom bombardment (FAB) at various ion kinetic energies (Elab values) on a hybrid tandem instrument produced ions of different intensities for the diastereomers. The ratio of NH3 to H2O loss is 0.3 for the L-Ala peptide but 1.7 for the D-Ala isomer at 5 eV. In some L-Ala spectra, the [M + H - NH3]+ ion does not appear at all. The y2 ion is up to twice as abundant in the L-Ala spectra as in the D-Ala, while the b2 ion is somewhat more abundant for CAD of the D-Ala peptide for most collision energies investigated. The D-Asp peptide produces a b2 ion that is more than half-again as abundant as in the case of the L-Asp isomer, and an [M + H - H2O]+ ion that is up to twice as abundant in the D-Asp CAD spectra as in those of the L-Asp. The y1, a2, and phenylalanine immonium ions are each up to twice as abundant in the L-Asp spectra as in those of the D-Asp isomer. The major differences are correlated with force-field calculations on hydrogen-bonded tautomers.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290070507
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  • 4
    Electronic Resource
    Electronic Resource
    Energy dependence of rearrangements of an N-terminal protecting group in tandem mass spectrometry of protonated tripeptides containing C-terminal argininePresented in part at the 39th ASMS Conference on Mass Spectrometry and Allied Topics, Nashville, TN, May 19-24, 1991. (1993)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 28 (1993), S. 113-122 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The types and intensities of tandem mass spectrometric products of side-chain interactions were investigated with a hybrid tandem instrument. Positive-ion unimolecular decomposition and collisionally activated decomposition studies were conducted on the [M + H]+ ions of two N-benzyloxycarbonyl (Cbz or Z)-protected tripeptides, Cbz-Gly-Leu-Arg-NH2 and Cbz-Gly-Pro-Arg-NH2. The loss of benzyl alcohol (108 u) and the formation of other significant product ions and their dependence on collision energy and gas pressure suggest reaction between both ends of the molecule. Replacement of leucine with proline at the second position in the tripeptide produces a very intense [M + H - 108]+ ion and fewer lower mass fragment ions in the tandem mass spectra for Cbz-Gly-Pro-Arg-NH2 than in those for Cbz-Gly-Leu-Arg-NH2.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210280210
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  • 5
    Electronic Resource
    Electronic Resource
    Dependence of benzyl alcohol loss on C-terminal amino acid in tandem mass spectrometry of N-protected tripeptidesTo recognize Professor J. L. Holmes's service to science as North American Editor of Organic Mass Spectrometry for many years. Presented in part at the 40th ASMS Conference on Mass Spectrometry and Allied Topics, Washington, DC, May 31-June 5, 1992. (1993)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 28 (1993), S. 1053-1058 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of the basicity and chain length of the C-terminal amino acid on the fragmentation of N-protected tripeptides was investigated with a hybrid tandem instrument. Positive-ion unimolecular decomposition and colisionally activated decomposition studies on the [M + H]+ ions of a series of N-benzyloxycarbonyl (Cbz or Z)-protected tripeptides, Cbz-Gly-Leu-Xxx-OMe and Cbz-Gly-Pro-Xxx-OMe, where Xxx = Arg, Lys, Orn, Gln and Glu, indicate that substitution of leucine with proline at the second position in the tripeptides facilitates the loss of benzyl alcohol (108 u) from the precursor. Additionally, higher gas-phase basicity and longer chain length of the C-terminal side-chain group promote the formation of the [M + H - 108]+ ion.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210281013
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