Influence of glycerol on the structure and stability of ferric horse heart myoglobin: a SAXS and circular dichroism study.

The influence of glycerol on the structural properties of Fe(III)-horse heart myoglobin has been investigated by absorbance, CD and SR-SAXS spectroscopy. The results obtained indicate that both the tertiary and the secondary (alpha-helix) conformations of the protein are influenced by glycerol; in particular, an increase of approx. 8% in helical content was observed. Further, analysis of both the acid- and guanidine-induced denaturation transitions points to a glycerol-induced decreased stability of the tertiary structure; conversely, the alpha-helix conformation is found to be stabilized by the organic solvent. Finally, the SR-SAXS data show that gyration radius, cross-section and thickness of the protein increase in the presence of the organic solvent; however, the protein maintains a compact state.