STUDIES CONCERNING BEHAVIOR OF ACTINOMYCIN IN SOLUTION

Dimerization and conformational change of actinomycin are investigated by equilibrium centrifugation and optical rotatory dispersion. A specific dimer forms in aqueous solutions of actinomycin, with a dimerization constant of roughly 103 M-1. The heat and entropy of dimerization are relatively large and negative. The optical rotatory dispersion spectrum of actinomycin depends on the nature of the solvent, presumably reflecting differences in molecular conformation. Changes in the optical rotatory dispersion spectrum seem to be correlated with the surface tension of the solvent. Results are discussed in terms of some qualitative ideas about the nature of hydrophobic interactions. © 1968, American Chemical Society. All rights reserved.