A 50TH ORDER REACTION PREDICTED AND OBSERVED FOR SICKLE HEMOGLOBIN NUCLEATION

Sickle hemoglobin polymerization exhibits a striking sensitivity to in itial concentration, with characteristic reaction times that exhibit s imilar to 30th power dependence on the concentration. This extraordina ry reaction order is encompassed by a novel double nucleation mechanis m that predicts similar to 50th power dependence of the homogeneous nu cleation rate. Using a technique that allows individual homogeneous nu cleation events to be monitored, we have measured a concentration depe ndence of 47 +/- 5, in excellent agreement with the predictions of the model. Absolute nucleation rates agree with predictions as well. (C) 1996 Academic Press Limited