Original scientific paper

Apparently Opposing Effects of Temperature and Guanidinium Chloride in the Denaturation of Ribonuclease A

S. Lapanje ; Department of Biochemistry, J. Stefan Institute and Department of Chemistry, University of LjubLjana, 61000 Ljubljana, Yugoslavia
R. Prijon ; Department of Biochemistry, J. Stefan Institute and Department of Chemistry, University of LjubLjana, 61000 Ljubljana, Yugoslavia
F. Gubenšek ; Department of Biochemistry, J. Stefan Institute and Department of Chemistry, University of LjubLjana, 61000 Ljubljana, Yugoslavia

Abstract

The thermal denaturation of ribonuclease A in the presence of
guanidinium chloride (GdmCl) was studied by means of circular
dichroism (CD). In the presence of GdmCl the transition temperatures
decrease with increasing denaturant concentration. However,
closer examination of the results obtained shows the following
feature: the negative values of molar ellipticity decrease with
temperature in the absence of the denaturant; after the addition
of the denaturant ellipticity minima appear at temperatures which
depend on the denaturant concentration. The higher the GdmCl
concentration the lower the temperature of the minimum. In 4
molar (and higher) GdmCl the minimum does not appear and the
negative molar ellipticity increases throughout the whole temperature
range examined. After reduction of the disulfide bonds,
similar behaviour is observed with the minimum at each denaturant
concentration being shifted towards a lower temperature. Though
there is no obvious explanation for this behaviour, it appears that
at the temperatures above the minimum some secondary structure
is regained owing to decreased protein denaturant interactions.

Keywords

Hrčak ID:

195942

URI

https://hrcak.srce.hr/195942

Publication date:

8.2.1979.

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