The Interaction of Chloroquine with the Albumin of Bovine Plasma

SUMMARY The interaction of chloroquine with bovine plasma albumin has been evaluated by spectrophotometric methods. In the physiological range of pH, chloroquine exists as an equilibrium mixture of two species which can be designated as B-B’Hf and +HB-B/H+, in which B represents the ring nitrogen and B’ the diethylamino nitrogen of the side chain. Albumin interacts reversibly with species B-B’H+ but does not interact with species +HB-B’H+. The value of the first apparent association exponent, log k’l, was determined to be 3.72 at 30” and ionic strength 1.66. BIBLIOGRAPHY 1. Irvin, J. L., and Irvin, E. M., J. Biol. Chem., 196, 651 (1952). 2. Irvin, J. L., and Irvin, E. M., J. Am. Chem. SOL, 69, 1091 (1947). 3. Debye, P., and Hiickel, E., Phys. Z., 24, 185 (1923). 4. Scatchard, G., Batchelder, A. C., and Brown, A., J. Clin. Invest., 23, 453 (1944). 5. Irvin, J. L., Irvin, E. M., and Parker, F. S., Science, 110, 426 (1949). 6. F&on, J. D.,