T H E Specific Heat and the Heat of Compression of Human Red Cells, Sick_led Red Cells, and Paracrystalline Rat Red Cells* by Eric Ponder

This paper is concerned with two thermal properties of red cells, paracrystalline red cells, and sickled red ceils. The first is their specific heats, which, generally speaking, can be expected to decrease as the degree of molecular orientation increases. The second is the thermal effect of compression, heating or cooling occurring on the application of pressure according to whether the orderliness of the molecules is decreased or increased. Since there is evidence that the molecules of the mammalian red cell are arranged to form a structure, well defined at the surface and much less well defined in the interior (Ponder, 1951), an investigation of the specific heats and the effects of compression may give a certain amount of information about the molecular orderliness which exists, particularly in the ease of cold pamcrystalline rat red cells (Ponder, 1945) and sickled red cells. There seems to be no doubt that the orderliness of the molecules in the cold paracrystalline rat red cell is greater than that in the normal red cell or in the paxacrystalline rat red cell when warmed (when it ceases to be paracrystalline), for both birefringence and x-ray spacings corresponding to 58 A and 45 A have been found (Dervichian, Fournet, Guinier, and Ponder, 1952), the birefringence and the spacings disappearing when the cells are warmed and reappearing in the cold. The passage from the normal to the paracrystalline form is also accompanied by a small but definite decrease in the specific heat (Ponder, 1953). The situation is not so dear in the case of the birefringent (Ascendi and Silverstroni, 1953) sickled red cell. Perutz and Mitchison (1950) have shown that hemogiobin-S is relatively insoluble, and because sickled red cells give anomalous colors slmilar to the dichroism seen in crystals of a reduced hemoglobin, have concluded that deoxygenation results in the crystallization of hemoglobin-S inside the cell, and that sickling is the result partly of the habit of the crystals and partly of the loss of water which would be expected to accompany crystallization. They suggest that this water diffuses out of the cell and that this results in the surface structure collapsing; measurements of water content show, how-