The oxygen affinity of chlorocruorin

Abstract

Chlorocruorin is a pigment which is red in concentrated solution and green in dilute solution. They only situation in which chlorocruorin is found is in the blood of Sabellid, Serpulid and Chlorhæmid polychæte worms, where it is in solution in the plasma. It is the only naturally occurring substance which both has similar properties to hæmoglobin and is chemically closely related to the latter. The principal chemical differences between the two pigments are that chlorocruorin has a different porphyrin and a different protein from hæmoglobin (Fox, 1926; Warburg and Negelein, 1932). I have lately studied the oxygen affinity of the specific chlorocruorin of Spirographis spallanzanii. Since only very small quantities of blood are obtainable from the worms, it was impossible to study whole blood, but was necessary to work with dilute solutions. A spectrographic technique was therefore adopted, which is possible since the absorption spectra of oxy-and reduced chlorocruorin differ in a similar way to those of oxy- and reduced hæmoglobin. The diluted blood, at definite temperatures and hydrogen ion concentrations, was equilibrated with atmosphere having known pressures of oxygen. After each equilibration the light absorption of the solution was measured at the two wave-length in the visible region of the spectrum at which there is the greatest difference between the oxidised and reduced forms of the pigment. From the data thus obtained the relative concentrations of the two forms were calculated.