Abstract
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.
Highlights
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
While there is good reason to think that carp carboxyhemoglobin may change from the R to T conformation on lowering the pH [6,7], there is less reason to suppose that changing the temperature alters the conformation of a series of hemoglobin A derivatives, and the specificity of the Adams and Schuster spectrum is open to some question
In our first experiments [13], like Fabry and Hunt, we were unable to find a clear effect of pressure on protohematin, and so thought that the protein was necessary to obtain the effect
Summary
Materials -Human hemoglobin was from hemolyzed human blood obtained bv caDillarv Duncture. The windows were 1 cm thick fused silica with a thickness to unsupported diameter ratio of 1:3 They were held in stainless steel plugs which screwed into the body of the chamber. In addition to the spectra of the hemoglobin derivatives themselves, base-lines for solvent at 1,100, and 1000 atm were recorded. These reflect changes in quantities such as stressinduced birefringence in the windows rather than changes in the solvent itself. Direct digital recording of spectra was performed using a laboratory-constructed instrument which has been described in detail elsewhere (Knowles and Gibson [10]) This is a simple split-beam spectrophotometer based on a Bausch and Lomb 500 mm f.1. 1000 atm spectrum has been corrected for an increase in absorbance of 4.5% caused by compression of the solution
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