  Double stranded DNA chain is known to have nontrivial elasticity. We study
the effect of this elasticity on the denaturation profile of DNA oligomer by
constraining one base pair at one end of the oligomer to remain in unstretched
(or intact) state. The effect of this constraint on the denaturation profile of
the oligomer has been calculated using the Peyrard-Bishop Hamiltonian. The
denaturation profile is found to be very different from the free (i.e. without
the constraint) oligomer. We have also examined how this constraint affects the
denaturation profile of the oligomer having a segment of defect sites located
at different parts of the chain.
