Evidence of Gumbel distributions of conductance fluctuations in bacteriorhodopsin thin films

By considering a set of experiments carried out on bacteriorhodopsin in vitro by Casuso et al (2007 Phys. Rev. E 76 041919), we extract the conductance as function of the applied voltage. The microscopic interpretation of experiments shows that charge transfer is ruled by a direct tunneling (DT) mec...

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Bibliographic Details
Published in:Journal of physics. Condensed matter 2013-09, Vol.25 (37), p.375103-7
Main Authors: Alfinito, E, Reggiani, L
Format: Article
Language:English
Subjects:
Analytical, structural and metabolic biochemistry
Bacteria
Bacteriorhodopsin
Bacteriorhodopsins - chemistry
Bias
Biological and medical sciences
Computer Simulation
Conductance
Dynamical systems
Electric Conductivity
Electric potential
Fluctuation
Fundamental and applied biological sciences. Psychology
General aspects, investigation methods
Models, Theoretical
Normal Distribution
Nucleation
Probability density functions
Proteins
Stochastic Processes
Thin films
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Summary:By considering a set of experiments carried out on bacteriorhodopsin in vitro by Casuso et al (2007 Phys. Rev. E 76 041919), we extract the conductance as function of the applied voltage. The microscopic interpretation of experiments shows that charge transfer is ruled by a direct tunneling (DT) mechanism at low bias and by a Fowler-Nordheim (FN) tunneling mechanism at high bias. A nucleation region at the cross-over between the DT and FN regimes can be identified. A theoretical analysis of conductance fluctuations is performed by calculating the corresponding variance and the probability density functions (PDFs): these constitute a powerful indicator in order to understand the internal dynamics of the system. Conductance fluctuations are non-Gaussian and follow well the standard generalized Gumbel distributions G(a). In particular, at low bias, the PDFs are bimodal and can be resolved in at least a couple of G(a) functions with different values of the shape parameter a. The nucleation region is characterized by a single Gumbel distribution, G(1). At increasing bias, the G(1) distribution turns in a bimodal distribution. We discuss possible correlations between the voltage dependence of the G(a) and the microscopic mechanisms that determine the electrical response of the system.
ISSN:0953-8984
1361-648X
DOI:10.1088/0953-8984/25/37/375103