Effect of hydrostatic pressure on spectra of heme compounds.

Increase in hydrostatic pressure shifts the absorption bands of oxy-, carboxy-, and deoxyhemoglobin and myoglobin toward the red by 0.4 to 0.7 nm corresponding to a change in extinction coefficient of from 4 to 8% at the peak of the difference spectrum. The pressure difference spectrum for oxyhemoglobin closely resembles the difference spectrum described by Adams and Schuster ((1974) Biochem. Biophys. Res. Commun. 58, 528-533) following addition of inositol hexaphosphate to oxyhemoglobin. A similar shift was observed for derivatives of dimethyl-deuterohemedisulfonate in both Fe2+ and Fe3+ forms indicating that the protein is not required for this effect, in contrast to earlier reports of T. L. Fabry and J. W. Hunt ((1968) Arch. Biochem. Biophys. R3, 428-429) and Q.H. Gibson and F.G. Carey ((1975) Biochem. Biophys. Res. Commun. 67, 747-571) who were unable to observe changes in aqueous solutions of protoheme derivatives.