Infrared spectroscopy of the water vapor sorption process of caseins

https://doi.org/10.1016/0005-2795(75)90122-1Get rights and content

Abstract

Infrared spectra of αs-, β- and micellar casein were studied at relative water vapor pressures (pp0) ranging from 0 to 0.98. The samples were prepared as self-supporting films by evaporating concentrated aqueous suspensions of the caseins under study. An infrared cell and a vacuum apparatus were constructed which allowed exposure of the casein films either to vacuum or to sorbate vapor.

Following the increase in intensities of the OH and O2H absorption bands during hydration, a sigmoid-shaped curve was observed, similar to the type II isotherm usually obtained by gravimetric sorption measurements. The pronounced frequency and intensity changes in the amide I, II and III bands in the pp0 range from 0 to about 0.10 lead to the conclusion that water molecules are already attached to the peptide repeat unit at very low humidities. Based on calculations of the amount of polar groups per casein molecule it was shown that much less than one water molecule per polar group is needed to cause these significant spectral changes.

References (25)

  • H. Susi et al.

    J. Biol. Chem.

    (1967)
  • S.N. Timasheff et al.

    J. Biol. Chem.

    (1967)
  • M. Rüegg et al.

    J. Dairy Sci.

    (1974)
  • H.E. Hallam

    Spectrochim. Acta

    (1969)
  • H.B. Bull et al.

    Arch. Biochem. Biophys.

    (1968)
  • T. Miyazawa
  • T. Miyazawa et al.

    J. Chem. Phys.

    (1958)
  • S. Krimm

    J. Mol. Biol.

    (1962)
  • H. Susi et al.

    Biopolymers

    (1971)
  • Y.N. Chirgadze et al.
  • V.C. Farmer et al.
  • C.L. Angell et al.

    J. Phys. Chem.

    (1965)
  • Cited by (12)

    • Cellular Water and Anhydrobiosis in Plants

      2015, Journal of Plant Growth Regulation
    • Water binding in sub-aerial cyanobacteria

      1998, Indian Journal of Biochemistry and Biophysics
    View all citing articles on Scopus
    View full text