Association of Radioactive Chromium with Various Components of Hemoglobin

1) When normal hemoglobin was labeled with Cr⁵¹ by incubation of whole blood with Na₂Cr⁵¹O₄, or by incubation of hemolysates with either Na₂Cr⁵¹O₄ or Cr⁵¹Cl₃, most of the Cr⁵¹ activity was associated with the electrophoretically rapid hemoglobin A₃. The formation of a Cr⁵¹ hemoglobin complex with an isoelectric point lower than that of hemoglobin was thought to be the most likely explanation of this finding.⁴

2) The radioactivity of Cr⁵¹-labeled hemolysates containing hemoglobin S, C, and A was found to be associated with the more rapid electrophoretic components. This finding supports the hypothesis of a lower isoelectric point of a Cr-hemoglobin complex.

3) The association of Cr⁵¹ activity with the polypeptide chains of hemoglobin was studied by two approaches: 1) determination of the labeling of components in hemolysates containing hemoglobin A (α^A₂ β^A₂) and hemoglobin H (β^A₄), and 2) determination of the labeling of polypeptide chains of Cr⁵¹-labeled normal hemoglobin separated by the method of Huehns and co-workers.¹² Cr⁵¹ activity was found in both the naturally occurring β chain component (hemoglobin H) and in the β chain component prepared by the method of Huehns and co-workers.¹² These findings support the hypothesis of others^5,6 that β chains of hemoglobin have a greater affinity for chromium than do α chains.