Davydov soliton

A. S. Davydov, Solitons in Molecular Systems, Reidel, Dordrecht, 1986. 

The essential difference between the SWAP and the Davydov Soliton (apart from numerical matters) lies in the effect of the acoustic deformation in the former it changes the electron inter site transfer energy, whereas in the latter it changes the on site exciton vibrational energy. The difference between on site and inter site will not show up for polarons larger than the lattice spacing. 

Carreri et al (13) found infra red absorptions in polypeptides and their model crystal acetanilide which they suggested might be the Davydov Soliton. However it is more likely that they are due to the remaining member of the quartet of Table 1, namely the imide vibration bound in a range of optic deformation (14). 

The stress we lay on the difference between optic and acoustic deformation is a reaction to the enormous literature on exclusively optic polarons in conjugated polymers. Yet as the Davydov Soliton and SWAP show, it is the acoustic deformation which dominates the motion of the polaron. In so far as it is motion which is the essential quality of a Soliton, it is the Acoustic deformation which it is essential to consider. In reality... 

Simulated coherent energy transfer in a hydrogen bonded amide chain arising from Fermi resonance has been modelled by Clarke and Collins . This interesting study is related to the Davydov soliton model which has been proposed for explaining energy transport in proteins. The role of similar nonlinear effects in simple organised chemical systems has yet to be established. 

Solitons, furthermore, represent a particular case of excitation to a metastable state.In the Davydov soliton, in particular, stretching of the C = 0 bond forms the polar excitation, stabilized by the surroundings which play the part of the elastic field. This soliton, too, provides a loss-free transport of energy. 

ABSTRACT We present a dynamical scheme for biological systems. We use methods and techniques of quantum field theory since our analysis is at a microscopic molecular level. Davydov solitons on biomolecular chains and coherent electric dipole waves are described as collective dynamical modes. Electric polarization waves predicted by Frohlich are identified with the Goldstone massless modes of the theory with spontaneous breakdown of the dipole-rotational symmetry. Self-organization, dissipativity, and stability of biological systems appear as observable manifestations of the microscopic quantum dynamics. 

Nonlinear dynamical effects on one-dimensional systems such as biomolecular chains, e.g., Davydov solitons, can also be analyzed in terms of boson condensation. " In the Frohlich wave case, the condensation... 

The operator ((, t) is the free exciton field. As a first step we are going to show that the c-number Davydov soliton ... 

In conclusion from the above formalism we can deduce that the Davydov soliton is the macroscopic envelope of the localized boson condensation of the excitation quanta /) induced by the j8 transformation (3.19). The vanishing of the coefficient G of the nonlinear term of Eq. (3.29), via Eq. (3.13), implies the disappearance of the soliton, which then looks like a necessary consequence of the nonlinearities of the dynamics. 

A measure of the dipole-dipole interaction energy between two adjacent monomers and of the anharmonicity of the chain can be obtained by an inspection of the bandwidth of the absorption band of the monomer excitation, that forms the exciton. For a-helix proteins in which inhomogeneous broadening has been eliminated by ordering processes of the samples, the bandwidth of the C = 0 absorption at 1660 cm gives evidence of the excitonlike collectivization of the vibrational C = O excitation along the chain. This is a prerequisite for the existence of Davydov solitons on the chain. 

In recent years, it has been suggested that Davydov solitons could actually occur on a number of one-dimensional chains of biological... 

Proteins, however, must function at biological temperatures, and to be useful, the Davydov soliton must survive at these temperatures. The first difficulty faced by the Davydov/Scott model was the question of the thermal stability of the Davydov soliton. The Davydov/Scott Hamiltonian includes two systems one, the amide I vibration, is treated as a quantum mechanical entity and the second, the vibrations of the peptide groups as a whole (or the changes in the hydrogen bond lengths) are very often treated classically, an approximation that shall be designated here as the mixed quantum-classical approximation. The first simulations of the Davydov/Scott model at finite temperature were performed within the mixed quantum/classical model and coupled the classical part of the system to a classical bath. The result was that the localized excitation dispersed in a few picoseconds at biological temperatures. However, this result clashed with another obtained in Monte... 

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