The stability of the three dimensional structure of horse skeletal muscle myoglobin was investigated using visible spectroscopy. Guanidium hydrochloride (GuHCl) of concentrations 0.4 0.8M have no observable effect on the three dimensional structure as indicated by monitoring the absorbance at 420nm. However, higher concentrations (1.0-3.0M) resulted in unfolding of the protein as indicated by the dip in absorption from 0.535 to 0.350.The requirement for high denaturant concentration to perturb the structure of myoglobin indicates the high stability of the protein. We conclude that high concentrations of the denaturant GuHCl, disrupts the 3-dimensional structure of myoglobin causing its unfolding, in a two- state process, due to weak binding to the protein, which can be studied spectrophotometrically
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