A CONSTANT RADIUS OF CURVATURE MODEL FOR THE ORGANIZATION OF DNA IN TOROIDAL CONDENSATES

Toroidal DNA condensates have received considerable attention for thei r possible relationship to the packaging of DNA in viruses and in gene ral as a model of ordered DNA condensation. A spool-like model has pri marily been supported for DNA organization within toroids. However, ou r observations suggest that the actual organization may be considerabl y different. We present an alternate model in which DNA for a given to roid is organized within a series of equally sized contiguous loops th at precess about the toroid axis. A related model for the toroid forma tion process is also presented. This kinetic model predicts a distribu tion of toroid sizes for DNA condensed from solution that is in good a greement with experimental data.