Charge Conductivity in Peptides: Dynamic Simulations of a Bifunctional Model Supporting Experimental Data

Our previous finding and the given mechanism of charge and electron transfer in polypeptides are here integrated in a bifunctional model involving electronic charge transfer coupled to special internal rotations. Present molecular dynamics simulations that describe these motions in the chain result...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2000-02, Vol.97 (3), p.1068-1072
Main Authors: Schlag, E. W., Sheu, Sheh-Yi, Yang, Dah-Yen, Selzle, H. L., Lin, S. H.
Format: Article
Language:English
Subjects:
Amino acids
Atoms
Biological Sciences
Biomolecules
Computer Simulation
Conductivity
Degrees of freedom
Electric Conductivity
Kinetics
Logic gates
Modeling
Models, Chemical
Models, Molecular
Molecules
Peptides
Peptides - chemistry
Physics
Rotation
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Summary:Our previous finding and the given mechanism of charge and electron transfer in polypeptides are here integrated in a bifunctional model involving electronic charge transfer coupled to special internal rotations. Present molecular dynamics simulations that describe these motions in the chain result in the mean first passage times for the hopping process of an individual step. This "rest and fire" mechanism is formulated in detail--i.e., individual amino acids are weakly coupled and must first undergo alignment to reach the special strong coupling. This bifunctional model contains the essential features demanded by our prior experiments. The molecular dynamics results yield a mean first passage time distribution peaked at about 140 fs, in close agreement with our direct femtosecond measurements. In logic gate language this is a strongly conducting ON state resulting from small firing energies, the system otherwise being a quiescent OFF state. The observed time scale of about 200 fs provides confirmation of our simulations of transport, a model of extreme transduction efficiency. It explains the high efficiency of charge transport observed in polypeptides. We contend that the moderate speed of weak coupling is required in our model by the bifunctionality of peptides. This bifunctional mechanism agrees with our data and contains valuable features for a general model of long-range conductivity, final reactivity, and binding at a long distance.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.97.3.1068