The sulphydryl groups of sickle-cell haemoglobin.

particularpH owing to the screening ofthe haematin iron atom from the influence of the various ionizing groups. On this basis a larger critical I would signify that a larger concentration of salt ions is required for complete screening, and hence that there is a stronger interaction between the iron and the ionizing groups in MetHb. In conclusion, although the mechanism may be different it may be noted that the Bohr effect, which is due to interaction between the iron and the specific haem-linked ionizing group, is greater in haemoglobin than in myoglobin.