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Register a new userNon-Arrhenius modes in the relaxation of model proteins
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Added by
Skorobogatiy Maksim
Publication date
1998
fields
Physics
and research's language is
English
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We have investigated the relaxational dynamics for a protein model at various temperatures. Theoretical analysis of this model in conjunction with numerical simulations suggests several relaxation regimes, including a single exponential, a power law and a logarithmic time dependence. Even though a stretched exponential form gives a good fit to the simulation results in the crossover regime between a single exponential and a power law decay, we have not been able to directly deduce this form from the theoretical analysis.
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We have exactly solved the relaxational dynamics of a model protein which possesses a kinetically perfect funnel-like energy landscape. We find that the dependence of the relaxation time, $tau$, on the density of states (DOS) and the energy level spacing distributions of the model displays several main types of behavior depending on the temperature $T$. This allows us to identify possible generic features of the relaxation. For some ranges of $T$, $tau$ is insensitive to the density of states; for intermediate values of $T$ it depends on the energy level spacing distribution rather than on the DOS directly, and it becomes gradually more dependent on DOS with increasing temperature; finally, the relaxation can also be determined exclusively by the presence of a deep gap in the energy spectrum rather than by the detailed features of the density of states. We found that the behavior of $tau$ crucially depends on the degeneracy of the energy spectrum. For the special case of exponentially increasing degeneracy, we were able to identify a characteristic temperature which roughly separates the relaxational regimes controlled by energetics and by entropy, respectively. Finally, the validity of our theory is discussed when roughness of energy landscape is added.
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