The chemical nature of hæmochromogen and its carbon monoxide compound

Abstract

In a previous communication (Hill, R., 1925) I summarised the properties of a number of derivatives of the blood pigment in which the iron was replaced by different metals. When iron combines with hæmatoporphyrin to give a hæmatin, the spectrum resembles that of a typical metallo-porphyrin only when the pigment is in the form of hæmochromogen. The nature of hæmochromogen has until quite recently not been understood. The work of Anson and Mirsky (1925) shows that hæmochromogen, prepared directly from oxyhæmoglobin by reduction in alkaline solution, is a compound between the pigment and the protein. Again, these workers state clearly that when other simpler substances are used instead of the protein, each substance gives its characteristic hæmochromogen by actual combination. They emphasised the fact that all substances capable of yielding typical hæmochromogens contained nitrogen, and showed that hæmochromogen is dissociated in solution into pigment and free nitrogen compound, to a greater or less extent depending on the particular hæmochromogen in question. Dilling (1910) had made a detailed qualitative study of hæmochromogens prepared by means of different reagents, but he does not seem clear as to the part played by the reduced hæmatin in the formation of hæmochromogen. The nearest approach to a solution of the problem previous to Anson and Mirsky’s work was that of Bertin Sans and de Moitessier (1893). These authors had shown that pure hæmatin when reduced with sodium hydrosulphite will not give hæmochromogen, unless albumen or certain amines were added. They failed, however, to exclude the possibility of the relation between pigment and nitrogenous substance being other than chemical combination. Von Zeynek (1910) analysed pyridine hæmochromogen and found that it contained 2·2 molecules of pyridine. He regarded it as a compound of hæmochromogen and pyridine. This work, therefore, gave no indication of the minimum amount of pyridine necessary to convert reduced hæmatin into hæmochromogen.