  The dynamics of a loop in DNA molecules at the denaturation transition is
studied by scaling arguments and numerical simulations. The autocorrelation
function of the state of complementary bases (either closed or open) is
calculated. The long-time decay of the autocorrelation function is expressed in
terms of the loop exponent c both for homopolymers and heteropolymers. This
suggests an experimental method for measuring the exponent c using florescence
correlation spectroscopy.
