Charge transfer in polypeptides: effect of secondary structures on charge-transfer integral and site energies |
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Authors: | Santhanamoorthi N Kolandaivel P Senthilkumar K |
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Affiliation: | Department of Physics, Bharathiar University, Coimbatore, India-641 046. |
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Abstract: | We have theoretically studied the charge transfer in glycine polypeptide using quantum mechanical models based on a tight-binding Hamiltonian approach. The charge-transfer integrals and site energies involved in the transport of positive charge through the peptide bond in glycine polypeptide have been calculated. The charge-transfer integrals and site energies have been calculated directly from the matrix elements of the Kohn-Sham Hamiltonian defined in terms of the molecular orbitals of the individual fragments of the glycine polypeptide. In addition to this, we have calculated the rate of charge transfer between a neighboring amino acid subgroup through the Marcus rate equation. These calculations have been performed for the different secondary structures of the glycine model peptide such as linear, alpha-helix, 3(10)-helix, and antiparallel beta-sheet by varying the dihedral angles omega, varphi, and psi along the Calpha-carbon of amino acid subgroup. Present theoretical results confirm that the charge transfer through the peptide bond is strongly affected by the conformations of the oligopeptide. |
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