Abstract
1. Haemoglobin, dissolved in an isotonic phosphate buffer solution of pH 6.7, i.e. the isoelectric point of haemoglobin, was heated at 55°C or 59°C for various periods, and its heat denaturation as well as its molecular aggregation were studied. Denaturation was indicated by loss of the oxygen-capacity, while the molecular aggregation process was observed from the decrease in colloidosmotic pressure, and also in the diminution of the Fe-content of the solution, from which the coagulated haemoglobin had been eliminated.
2. Denaturation is quite a different process from molecular aggregation, as the former proceeds much more rapidly than the latter. Both these processes may take place at the isoelectric point of haemoglobin.
3. At a lower temperature (55°C), a marked progress in denaturation is observed, while the molecular aggregation proceeds only to a slight extent.
4. On raising the temperature (59°C), the molecular aggregation is accelerated more rapidly than the denaturation so that the former may catch up after a certain duration of heating. Even at this stage, a certain portion of the aggregated haemoglobin does not form a coagulum eliminable by filtration or centrifuging.
