Observation of dielectric universalities in albumin, cytochrome C and Shewanella oneidensis MR-1 extracellular matrix

Abstract

The electrodynamics of metals is well understood within the Drude conductivity model; properties of insulators and semiconductors are governed by a gap in the electronic states. But there is a great variety of disordered materials that do not fall in these categories and still respond to external field in an amazingly uniform manner. At radiofrequencies delocalized charges yield a frequency-independent conductivity σ 1(ν) whose magnitude exponentially decreases while cooling. With increasing frequency, dispersionless conductivity starts to reveal a power-law dependence σ 1(ν)∝ν s with s < 1 caused by hopping charge carriers. At low temperatures, such Universal Dielectric Response can cross over to another universal regime with nearly constant loss ε″∝σ1/ν = const. The powerful research potential based on such universalities is widely used in condensed matter physics. Here we study the broad-band (1–1012 Hz) dielectric response of Shewanella oneidensis MR-1 extracellular matrix, cytochrome C and serum albumin. Applying concepts of condensed matter physics, we identify transport mechanisms and a number of energy, time, frequency, spatial and temperature scales in these biological objects, which can provide us with deeper insight into the protein dynamics.

Redox chemistry in the pigment eumelanin as a function of temperature using broadband dielectric spectroscopy

“…The boson peak is observed in disordered materials in the form of an excess contribution to the vibrational density of states (VDOS) g(n), relative to the Debye component g D (n) $ n 2 . This additional contribution can be observed by inelastic neutron or Raman scattering [62][63][64][65][66][67] and as a peak in the specic heat plotted as c P (T)/T 3 vs. T. 56,68 Furthermore, there is a remarkable observation which comes from the inset on Fig. 6A.…”

“…However, when cooled down, the strong dispersion observed for 3 0 (n) and 3 00 (n) weakens signicantly and both spectra nearly atten at around 150 K. The nearly constant imaginary permittivity, 3 00 (n) z const, together with the corresponding conductivity s 1 (n) $ 3 00 n $ n 1 behavior indicate emergence of the nearly-constant loss regime frequently observed in biological and disordered systems. [50][51][52][53][54][55][56] In contrast, the dry sample appears to be in a nearly constant loss regime already at room temperatures, with cooling only having a minimal effect. This indicates the clear effect that water has on melanin's electrical properties in promoting a hopping regime for conductivity (see below).…”

“…39 To model the terahertz spectra (included in Fig. 2) we used a Lorentzian expression that describes the resonance located above our highest frequency, and the Debye expression 56 to reproduce the response of water molecules (free or bound) clearly seen at T ¼ 325 K in the spectra of Fig. 5 (note the changes in the value is non zero).…”

Impedance spectroscopy of single bacterial nanofilament reveals water-mediated charge transfer

“…In the study we used either individual nanowires or the groups of spatially separated nanowires completely detached from bacterial bodies. The procedure of cultivation was described in details in Motovilov et al [ 31 ]. Briefly, we grew Shewanella oneidensis MR-1 strain in anaerobic anodic chambers of original microbial fuel cells.…”

Terahertz-infrared spectroscopy of Shewanella oneidensis MR-1 extracellular matrix

“…The enormous sensitivity of optical spectra to the presence of water fractions in samples is another feature of the technique that can be utilized in the search for ionic conductivity. In our previous work [20], we have performed detailed spectroscopic investigations of charge transport mechanisms in lyophilized S. oneidensis MR-1 extracellular matrix and filaments (EMF). Radio-frequency (ν = 1 Hz -300 MHz) and terahertz (ν = 0.1-1.6 THz) spectra of complex dielectric permittivity ε*(ν,T) = ε′(ν,T) + iε″(ν,T) and real part of AC conductivity σ(ν,T)=νε″(ν,T)/2 of EMF and of two reference materials, cytochrome c (cytC) and bovine serum albumin (BSA), were measured at temperatures 10-300 K. Analysis of the radio-frequency response revealed in EMF clear signatures of freecarrier and hopping (presumably ionic) mechanisms of electrical charge transport.…”