Collect. Czech. Chem. Commun. 1992, 57, 2192-2198

A Spectrophotometric Study of Reversibility of Human Mercaptoalbumin Denaturation by Urea

Josef Chmelíka, Petr Kálalb and Vítěz Kalousc

a Institute of Analytical Chemistry, Czechoslovak Academy of Sciences, 611 42 Brno, Czechoslovakia
b Ontario Hydro, Research Division, Toronto, M8Z 5S4, Canada
c Department of Physical and Macromolecular Chemistry, Charles University, 128 40 Prague, Czechoslovakia


The renaturation of the human mercaptoalbumin denaturated by urea has been studied spectrophotometrically. The denaturation is reversible up to 15 min treatment with 8 mol dm-3 urea, whereas a longer treatment brings about irreversible changes of the mercaptoalbumin molecule. Samples have been prepared of the renatured mercaptoalbumin pre-denatured by 8 mol dm-3 urea for a period of either 1 min or 200 min. The temperature perturbation differential and derivation spectrophotometries were used to investigate the localization of tyrosyl residues in native mercaptoalbumin and in the renatured forms. From the results it follows that the localization of tyrosyls in the renatured mercaptoalbumin after 1 min denaturation by 8 mol dm-3 urea is the same as that in native protein. On the other hand, the renaturated mercaptoalbumin after 200 min denaturation contains a great number of exposed tyrosyls than is the number in the native protein.