title: Large oxidation dependence observed in terahertz dielectric response for cytochrome c.
abstract: Far infrared dielectric response is used to characterize the collective mode density of states for cytochrome c as a function of oxidation state and hydration using terahertz time domain spectroscopy. A strong absorbance and refractive index increase was observed with the oxidation. A simple phenomenological fitting using a continuous distribution of oscillators reproduces the frequency dependence of the complex dielectric response as well as demonstrates quantitative agreement with a uniform increase in either mode density or polarizability with oxidation in the 5-80 cm(-1) frequency range. Hydration dependence measurements find that a difference in the equilibrium water content for ferri and ferro cytochrome c is not sufficient to account for the large change in terahertz response. The large dielectric increase at terahertz frequencies with oxidation suggests either a significant global softening of the potential and/or a significant increase in polarizability with oxidation.
authors.affiliation: Physics Department, University at Buffalo, SUNY, Buffalo, New York 14260, USA.
authors.forename: J-Y
authors.initials: JY
authors.lastname: Chen
authors.forename: J R
authors.initials: JR
authors.lastname: Knab
authors.forename: J
authors.initials: J
authors.lastname: Cerne
authors.forename: A G
authors.initials: AG
authors.lastname: Markelz
mesh_terms: D003198:Computer Simulation; D045304:Cytochromes c / Q000737:chemistry* / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D007259:Infrared Rays; D008956:Models, Chemical; D010084:Oxidation-Reduction / Q000528:radiation effects; D011829:Radiation Dosage; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; D045304:Cytochromes c