  A class of nucleosome remodeling motors translocate nucleosomes, to which
they are attached, toward the middle of DNA chain in the presence of ATP during
in vitro experiments. Such a biological activity is likely based on a physical
mechanism for detecting and comparing the lengths of the flanking polymer
chains. Here we propose that a pivoting mode of DNA fluctuation near the
surface of the nucleosome coupled with binding reaction with a DNA binding site
of the motor provides a physical basis for length detection. Since the mean
frequency of fluctuation is higher for a shorter chain than a longer one due to
its lower drag coefficient, a shorter chain has a higher rate of receptor
binding, which triggers the ATP-dependent activity of the remodeling motor.
Dimerization of such units allows the motor to compare the length of the
flanking DNA chains, enabling the translocation of the nucleosome toward the
center of the DNA.
