Carbon Monoxide Affinity of Chlorocruorin and Hæmoglobin

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CHLOROCRUORIN, the green-red respiratory blood pigment of certain marine annelid worms, is the only known substance built on the same plan as hæmoglobin. Like most kinds of hæmoglobin, chlorocruorin has a higher affinity for carbon monoxide than for oxygen1. This property, valueless to animals, is utilized in experimental work to eliminate the possible respiratory activity of these pigments and so to test their functional significance2,3. The relative affinity of chlorocruorin (Ch), or of hæmoglobin, for the two gases in the reversible reaction is given by the equilibrium constant K in the equation , from which it is seen that when the pigment is 50 per cent in the carboxy state and 50 per cent in the oxy state, K becomes the ratio of oxygen to carbon monoxide.

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FOX, H. Carbon Monoxide Affinity of Chlorocruorin and Hæmoglobin. Nature 162, 20 (1948) doi:10.1038/162020a0

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