Protein response to external electric fields: Relaxation, hysteresis, and echo
- Univ. of Illinois, Urbana, IL (United States)
Dipole moments induced in proteins by external electric fields are studied by molecular dynamics simulations and described in terms of analytical models based on ensembles of Langevin oscillators and Fokker-Planck equations. We investigate through simulations of the protein bovine pancreatic trypsin inhibitor (BPTI) (1) the distribution p(M) of dipole moments as well as the dipole moment autocorrelation function C{sub M,M}(t) at thermal equilibrium, (2) the dielectric constant {epsilon}, (3) the dipole moment {Delta}M(t) induced by cyclic (piecewise linear or sinusoidally periodic in time) spatially homogeneous fields, demonstrating significant hysteresis behavior, and (4) the dipolar responce to a constant homogeneous field applied for about a picosecond. Through a comparison between an analytical model and simulations, we show that the dipolar response (4) can be described by a relaxation characterized by C{sub M,M}(t) in addition to a significant pulse-shaped component, termed the dipole echo. The hysteresis behaviour (3) under a weak external field is related to the equilibrium properties p(M), C{sub M,M}(t), and {epsilon}. In the case of electric fields arising through charge displacements in proteins, e.g., through electronic excitation or photoinduced electron transfer, concomitant dipolar responses in real proteins should resemble those reported here and should be observed by means of sub-picosecond spectroscopy. 53 refs., 17 figs.
- OSTI ID:
- 380813
- Journal Information:
- Journal of Physical Chemistry, Vol. 100, Issue 29; Other Information: PBD: 18 Jul 1996
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BASIC STUDIES
40 CHEMISTRY
99 MATHEMATICS
COMPUTERS
INFORMATION SCIENCE
MANAGEMENT
LAW
MISCELLANEOUS
PROTEINS
RELAXATION
HYSTERESIS
DIPOLE MOMENTS
ELECTRON TRANSFER
ELECTRIC FIELDS
MOLECULAR MODELS
SIMULATION
MATHEMATICAL MODELS
PHOTOCHEMICAL REACTIONS
ENZYME INHIBITORS
DIELECTRIC PROPERTIES