CAN ONE MEASURE THE FREE-ENERGY OF BINDING OF THE HISTONE OCTAMER TO DIFFERENT DNA-SEQUENCES BY SALT-DEPENDENT RECONSTITUTION

I explain why many recently reported measurements for the "free energy" of positioning of the histone octamer on different DNA sequences are likely to be in error: i.e. because histone octamers do not equilibrate between different DNA molecules at low salt, but only at high salt. Thus, the reported "free energies" refer to an equilibrium at high salt, under nearly dissociating conditions between protein and DNA, and they are likely to be much too small on an absolute scale. There are many other lines of evidence to suggest that the preferences of the histone octamer for different DNA sequences are rather strong and of importance in biological systems. © 1991.