Nonlinear excitations in a disordered alpha-helical protein chain

We investigate the dynamics of alpha-helical proteins with dipole and quadrupole type molecular excitations. Performing the symbolic computation on the iterative algorithm of Darboux transformation, we present the multisoliton solutions for the resulting fourth order nonlinear Schrödinger (NLS) equation and study the energy sharing properties. We also study the effect of disorder (inhomogeneity) using the perturbative technique and found that the inhomogeneity in the hydrogen bonding spines introduces fluctuations in the profile of the solitons without affecting their robust nature and the propagation.