Conformational changes in proteins induced by low temperatures: an infrared study.

Infrared spectra of hemoglobin (met-hemoglobin) and myoglobin were recorded in the temperature range -110 degrees C to 30 degrees C. On cooling hydroalcoholic solutions of hemoglobin, the spectra indicate a conformational change (revealed by the appearance of a band at 1665 cm-1) compatible with the appearance of distortions in its alpha-helical structure. In the case of myoglobin smaller effects are observed. These conformational changes are entirely reversible and do not occur in frozen aqueous solutions.