MICROENVIRONMENT OF OXYGEN CARRIERS 323 



of Planorbis is found to be 33.7 between ^H 3 and pH 8. At lower pH the 

 molecule dissociates into smaller components (c/. Section 3.5.). The fric- 

 tional ratio {2721, Table 48, p. 406) is about 1.4 and the partial specific 

 volume, 0.745. Assuming that the hydration is approximately the same 

 as that of hemoglobin, w = 0.3, the axial ratio a/b calculated from Oncley's 

 diagram {2075, p. 131) is approximately equal to 5 or 0.18 according to 

 whether the molecule is considered to be a prolate or an oblate ellipsoid. 

 The molecular weight for a molecule containing 96 Hufner units is 1.69 

 million, the value found for erythrocruorin is 1.54 million. It is obvious 

 that the units are not joined end to end to give a threadlike molecule since 

 this would not agree with the value found for the frictional ratio and, more- 

 over, might give rise to optical anisotropy, so the units must be packed in 

 some relatively compact arrangement. Such a molecule would contain many 

 "crevices" and "splits" into which the prosthetic group could fit, as well as 

 salts or other substances. 



7.2. Erythrocyte 



7.2.1. Concentration of Hemoglobin. The concentration of hemoglobin 

 found in erythrocytes is approximately 34% and the pH about 7.4. Once 

 the hemoglobin is removed from the erythrocyte, it is certain that, at least 

 in some species, concentrations as great as this cannot be obtained at the 

 same pH. This fact is, of course, made use of in many of the methods for 

 preparing hemoglobin since in several species hemolysis of the erythrocyte 

 leads to spontaneous crystallization.* 



7.2.2. Spectrum of Hemoglobin within the Erythrocyte. While the spec- 

 trum of the erythrocyte in the visible region and probably also in the infrared 

 {ISJtS) is the same as that of the hemoglobin prepared from it, Adams and 

 co-workers {12) were not able to detect the So ret band in erythrocytes. 

 They claimed that this was due to combination of hemoglobin with stromatin 

 {11). Keilin and Hartree {1495) confirmed their finding that the Soret band 

 was absent in suspensions of erythrocytes but were unable to find any 

 spectroscopic change when hemoglobin was incubated with stromatin. They 

 showed, however, that the Soret band disappears when olive oil was emulsified 

 in a strong hemoglobin solution, and concluded that this was due, not to 

 any alteration of the hemoglobin, but to the optical properties of the dis- 

 continuous medium. This conclusion has now been shown to be corred by 

 several workers {4-64^,1381,1428). There is no evidence therefore that the 

 spectrum of the pigment within the cell is in any way abnormal. 



7.2.3. Oxygen Affinity. Hemoglobin is associated with substances in the 

 erythrocyte which affect its affinity for oxygen. Their action explains in 

 part the increase in affinity found when laked cells are diluted. Hill and 

 Wolvekamp {1286) observed that the effect was greater in the blood of some 



* Recent investigations by Dervichian, Fournet, and Guinier {566a) and by Perutz 

 {2136a) show that freely rotating hemoglobin molecules are arranged in the erythrocyte 

 in a close-packed lattice, and that their arrangement is comparable to the order in a 

 liquid metal, intermediate between that in a solid crystal and that in a dilute solution. 



