  In E. coli, accurate cell division depends upon the oscillation of Min
proteins from pole to pole. We provide a model for the polar localization of
MinD based only on diffusion, a delay for nucleotide exchange, and different
rates of attachment to the bare membrane and the occupied membrane. We derive
analytically the probability density, and correspondingly the length scale, for
MinD attachment zones. Our simple analytical model illustrates the processes
giving rise to the observed localization of cellular MinD zones.
