  We study the electronic structure of Ca2-xNaxCuO2Cl2 and Bi2Sr2CaCu2O8+d
samples in a wide range of doping, using angle-resolved photoemission
spectroscopy, with emphasis on on the Fermi surface (FS) in the near anti-nodal
region. The "nesting wave vector", i.e., the wave vector that connects two
nearly flat pieces of the Fermi surface in the anti-nodal region, reveals a
universal monotonic decrease in magnitude as a function of doping. Comparing
our results to the charge order recently observed by scanning tunneling
spectroscopy (STS), we conclude that the FS nesting and the charge order
pattern seen in STS do not have a direct relationship. Therefore,the charge
order likely arises due to strong correlation physics rather than FS nesting
physics.
