Nonlinear Migration Dynamics of Excess Electrons along Linear Oligopeptides Controlled by an Applied Electric Field

Migration of an excess electron along linear oligopeptides governed by the external electric field (E-ex) which is against the inner dipole electric field is theoretically investigated, including the effects of E-ex on the structural and electronic properties of electron migration. Two structural properties including electron-binding ability and the dipole moment of linear oligopeptides are sensitive to the E-ex values and can be largely modulated by E-ex due to the competition of E-ex and the inner electric field and electron transfer caused by E-ex. In the case of low E-ex values, two structural properties decrease slightly(,) while for high E-ex values, the electron-binding ability continually increases strongly, with dipole moments firstly increasing significantly and then increasing more slowly at higher E-ex. Additionally, linear oligopeptides of different chain lengths influence the modulation extent of E-ex and the longer the chain length is, the more sensitive modulation of E-ex is. In addition, electronic properties represented by electron spin densities and singly occupied molecular orbital distributions vary with E-ex intensities, leading to an unusual electron migration behavior. As E-ex increases, an excess electron transfers from the N-terminus to the C-terminus and jumps over a neighboring dipole unit of two termini to other units, respectively, instead of transferring by means of a one-by-one dipole unit hopping mechanism. These findings not only promote a deeper understanding of the connection between E-ex and structural and electronic properties of electron transfer behavior in peptides, but also provide a new insight into the modulation of electron migration along the oligopeptides.