Lattice stretching bistability and dynamic heterogeneity.
A simple one-dimensional lattice model is suggested to describe the experimentally observed plateau in force-stretching diagrams for some macromolecules. This chain model involves the nearest-neighbor interaction of a Morse-like potential (required to have a saturation branch) and a harmonic second-neighbor coupling. Under an external stretching applied to the chain ends, the intersite Morse-like potential results in the appearance of a double-well potential within each chain monomer, whereas the interaction between the second neighbors provides a homogeneous bistable (degenerate) ground state, at least within a certain part of the chain. As a result, different conformational changes occur in the chain under the external forcing. The transition regions between these conformations are described as topological solitons. With a strong second-neighbor interaction, the solitons describe the transition between the bistable ground states. However, the key point of the model is the appearance of a heterogenous structure, when the second-neighbor coupling is sufficiently weak. In this case, a part of the chain has short bonds with a single-well potential, whereas the complementary part admits strongly stretched bonds with a double-well potential. This case allows us to explain the existence of a plateau in the force-extension diagram for DNA and α-helix protein. Finally, the soliton dynamics are studied in detail.
Department of Informatics, Technical University of Denmark, Kgs. Lyngby, Denmark.
P L
PL
Christiansen
A V
AV
Savin
A V
AV
Zolotaryuk
D000465:Algorithms; D001703:Biophysics / Q000379:methods*; D003198:Computer Simulation; D004247:DNA / Q000737:chemistry*; D006858:Hydrofluoric Acid / Q000737:chemistry; D006860:Hydrogen Bonding; D007700:Kinetics; D008956:Models, Chemical; D015233:Models, Statistical; D008968:Molecular Conformation; D009218:Myosins / Q000737:chemistry; D009690:Nucleic Acid Conformation; D010825:Physics / Q000379:methods*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry*
D011506:Proteins; D004247:DNA; D009218:Myosins; D006858:Hydrofluoric Acid