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  • 2005-2009
  • 1980-1984  (2)
  • 1925-1929
  • 1910-1914
  • Circular dichroism  (1)
  • SAXS  (1)
  • 1
    ISSN: 1435-1536
    Keywords: Bovine serum albumin ; Heat denaturation ; Isoelectric focusing ; Hydrogen ion titration curve ; Circular dichroism ; Fluorescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract When the solution of bovine serum albumin at pH 9 is incubated at 65 °C, new components 1' (modified monomer), 2 (dimer) and 3 (probably trimer) are formed. The isoelectric focusing indicated that the isoelectric points of components 1', 2 and 3 were pH 5.9. The hydrogen ion titration curve for the native albumin had well known abnormal steepness at pH near 4, but that for component 1' had no abnormal steepness. The titration curve for component 1' located right side of that for the native albumin. Circular dichroism measurements indicated that some unfolding occurred, when the native albumin was changed to component 1'. The contents ofα-helix were 74 and 52 % for the native albumin and for component 1', respectively. The contents of β-structure were 19 and 23 % for the native albumin and for component 1', respectively. The wavelength of maximum intensity of tryptophan fluorescence shifted to lower wavelength, when the native albumin was changed to component 1'. This suggests that tryptophan residue(s) is transferred to a more hydrophobic environment. The hydrogen ion titration curves, circular dichroism and fluorescence measurements, all supported the possibility that the component 2 is formed by the dimerization of component 1'. Further, it has been found that component 2' (dimer impurity in commercial bovine serum albumin preparations) is formed by the direct dimerization of native bovine serum albumin without conformational change.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1435-1536
    Keywords: Mn(II) and Ni(II) salts of E-AA ; Ion-Clusters ; Dielectric Relaxation ; ESR ; SAXS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Zusammenfassung Die Existenz von Ionen-Aggregaten in Äthylen-Acrylsäure-Mischpolymerisaten, die durch Mangan-acetat und Nickel-acetat neutralisiert wurden, wurden durch dielektrische Messungen im Temperaturbereich von -180 bis 80 °C und für einige Frequenzen zwischen 30 Hz und 100 kHz, studiert. Dieβ′- undγ-Relaxationsprozesse wurden beobachtet, die durch die Mikro-Brownschen Molekülbewegungen im höheren Temperaturbereich vonT g und durch lokale Molekülbewegungen im tieferen Temperaturbereich vonT g verursacht werden. Die Veränderung in Intensität und Relaxationstemperatur für die beiden Relaxationsprozesse mit dem Grad der Neutralisation deutet auf die Bildung von Ionen-Aggregaten in Bereichen höherer Neutralisation als einem Wert zwischen 3.3 und 14% für das Mn(II)-Salz und als 14% für das Ni(II)-Salz an. Diese Bildung von Ionen-Aggregaten wurde ebenso durch Elektronenspinresonanz (ESR) und durch Kleinwinkel-Röntgenstreuung (KWRS) nachgewiesen. Die ESR-Spektren in den Mn(II)-Salzen zeigen sechs Absorptionen bei 14% Neutralisation und eine Absorption bei 62%. Die KWRS deutet auf die Existenz von Ionen-Aggregaten hin, deren Durchmesser ungefähr 27 Å für das Mn(II)-Salz und 19–23 Å für das Ni(II)-Salz bei höherer Neutralisation als 14% ist.
    Notes: Summary The existence of ion-clusters in ethylene-acrylic acid copolymers (mole% of acrylic acid is 9.3) neutralized with manganese(II) and nickel(II) acetates, respectively, was studied by dielectric measurements in the temperature range of −180 to 80 °C at several frequencies between 30 Hz and 100 kHz. Theβ′ relaxation due to a micro-Brownian molecular motion aboveT g and theγ relaxation due to a local molecular motion belowT g were observed. Variation in the magnitude and the relaxation temperature of the two relaxations with degree of neutralization by manganese/nickel acetate suggest the formation of ion-clusters in the higher degrees of neutralization above a value between 3.3 and 14% for the Mn(II) salts and above about 14% for the Ni(II) salts. Furthermore, this formation of ion-clusters was evidenced by electron spin resonance and small angle X-ray scattering studies. The ESR spectra for the Mn(II) salts exhibited six peaks at 14% of degree of neutralization and one peak at 62%. This indicates the existence of ion-clusters at 62%. The small angle X-ray scatterings suggested the existence of ion-clusters of diameter of about 27 Å for the Mn(II) salts and 19–23 A for the Ni(II) salts, at the high degrees of neutralization above 14%.
    Type of Medium: Electronic Resource
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