Kinetics of hemoglobin-carbon monoxide reactions measured with a superconducting magnetometer: a new method for fast reactions in solution.

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Abstract
A new technique for measuring fast reactions in solution was demonstrated. The changes in magnetic susceptibility during the recombination reaction of human Hb with CO after flash photolysis were measured with a new high-sensitivity instrument using cryogenic technology. The rate constants determined at 20.degree. C (pH 7.3) are in excellent agreement with those obtained by photometric techniques. A unique capability of this new method is the determination of the magnetic susceptibilities of short-lived reaction intermediates. The magnetic moment of the intermediate species Hb4(CO)3 was 4.9 .+-. 0.1 .mu.B in 0.1 M phosphate buffer by partial photolysis experiments. This value agrees with the predictions of 2-state allosteric models of cooperativity in Hb. Possible applications and improvements in this technique are discussed.