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  • conformation  (2)
  • BREAST-CANCER
  • 1985-1989  (2)
  • 1
    ISSN: 1573-4943
    Keywords: ovalbumin ; CD studies ; guanidine ; urea ; sodium dodecyl sulfate ; conformation ; secondary structure ; denaturation-renaturation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract By simulation of the circular dichroic spectra (Greenfield and Fasman (1969)) and using reference spectra of Chen et al. (1974), native ovalbumin was estimated to contain 33% α-helix, 5% β-structure, and 62% random coil. Ovalbumin resisted conformational changes in solutions of urea and of SDS. However, guanidine induced transition, starting at about 2 M and completing at about 4.5 M. At concentrations exceeding 4.5 M guanidine, ovalbumin existed as 6–7% α-helical, 12–13% β-structure, and 80–81% random coil. Ovalbumin after denaturation in 6 M guanidine or in 8 M urea (incubated at 4°C for 24 hr) did not recover the native conformation but acquired a new conformation in each case, with a somewhat destabilized helical structure.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-4943
    Keywords: sulfhydryl-blocked ovalbumin ; secondary structure ; conformation ; circular dichroic studies ; reduced ovalbumin ; denaturation profiles in guanidine, urea, and sodium dodecyl sulfate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Sulfhydryl groups of ovalbumin were chemically modified under denaturing conditions in the absence and presence of dithiothreitol, and effects on the secondary structure of the protein were investigated by circular dichroic (CD) measurements. The contents of α-helix, β-structure, and “random coil” (unordered, nonrepetitive structure) were estimated by simulation of the CD spectra and using the parameters established by Chen et al. The principal findings were these: (1) Modification of the four free sulfhydryl groups [with 5,5′-dithiobis(2-nitrobenzoic acid), iodoacetate, or iodoacetamide] caused ovalbumin molecule to unfold partially and to undergo primarily helix-to-β structure transition. (2) Cleavage of the disulfide bond did not lead to a further conformational change in the sulfhydryl-modified ovalbumin. (3) The remaining helical structure existed in a destabilized state with increased chain flexibility, as the modified protein was very susceptible to denaturation by guanidine and urea. (4) Further evidence for increased chain flexibility was provided by the finding that sodium dodecyl sulfate (SDS) induced helix formation in the sulfhydryl-modified, but not native, ovalbumin. And (5), since both nonreduced and reduced proteins, with their sulfhydryl groups blocked, displayed similar transitions in solutions of guanidine, urea, and SDS suggested that the single disulfide bond did not physically constrain the ovalbumin molecule.
    Type of Medium: Electronic Resource
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