The denaturation and propagation of a nonlinear localized excitation i
n DNA molecules are studied in a unified way for a new Hamiltonian. Th
e large amplitude motion of DNA is investigated during the propagation
of the nonlinear localized excitation. The nonlinear effect on the fo
rmation of the localized excitation is disscussed. It is shown that ou
r model not only can reproduce the results of denaturation experiments
, but also can describe the process of the localized excitation of flu
ctuational opening in DNA molecules. (C) 1997 Elsevier Science B.V.