Physica A 451 (2016) 533–540 Contents lists available at ScienceDirect Physica A journal homepage: www.elsevier.com/locate/physa Open channel current noise analysis of S6 peptides from KvAP channel on bilayer lipid membrane shows bimodal power law scaling Rajan Shrivastava a,1 , Chetan Malik b,1 , Subhendu Ghosh a,c,* a Department of Biophysics, University of Delhi South Campus, New Delhi, 110021, India b Department of Life Science, School of Sciences, Indira Gandhi National Open University, New Delhi, 110068, India c Centre for Information Services and High Performance Computing (ZIH), Technical University Dresden, Germany highlights • Power spectral density (PSD) of S6 single-channel open current traces has been analysed. • Bimodal slope of PSD (1/f and 1/f 2 ) in ion channels has been reported. • Two modes of non-equilibrium ion transport in S6 channel best describe the bimodal Power law scaling. article info Article history: Received 2 September 2015 Received in revised form 17 December 2015 Available online 6 February 2016 Keywords: Ion-channel S6 peptide Noise analysis Brown noise 1/f noise Bilayer electrophysiology abstract Open channel current noise in synthetic peptide S6 of KvAP channel was investigated in a voltage clamp experiment on bilayer lipid membrane (BLM). It was observed that the power spectral density (PSD) of the component frequencies follows power law with different slopes in different frequency ranges. In order to know the origin of the slopes PSD analysis was done with signal filtering. It was found that the first slope in the noise profile follows 1/f pattern which exists at lower frequencies and has high amplitude current noise, while the second slope corresponds to 1/f 2-3 pattern which exists at higher frequencies with low amplitude current noise. In addition, white noise was observed at very large frequencies. It was concluded that the plausible reason for the multiple power-law scaling is the existence of different modes of non-equilibrium ion transport through the S6 channel. © 2016 Elsevier B.V. All rights reserved. 1. Introduction Noise analysis is an important part of research in various fields, e.g. Physics, Geology, Environmental Sciences and Biology [1–3]. In physiology, a number of reports related to noise have come up over the last several years [4]. In general, Power law noise can be broadly classified into two categories, i.e. white noise (1/f 0 ) and coloured noise (1/f 1-3 )[5]. The origin and importance of various types of noise like 1/f 0 , 1/f , 1/f 2 and 1/f 3 , have been reported by many authors [6–12]. Especially, 1/f noise has been discussed extensively [7,13–16]. Bak et al. invoked Self Organized Criticality (SOC) to explain 1/f noise in sandpile avalanche [6–8]. He discussed the idea of criticality in phase transition of a dynamical system without * Corresponding author at: Department of Biophysics, University of Delhi South Campus, New Delhi, 110021, India. Tel.: +91 11 24113106x279; fax: +91 11 24115270. E-mail address: profsubhendu@gmail.com (S. Ghosh). 1 Both the authors contributed equally to this work. http://dx.doi.org/10.1016/j.physa.2016.01.079 0378-4371/© 2016 Elsevier B.V. All rights reserved.