Analyzing alpha-hemolysin nanopore behavior using Lempel-Ziv complexity

The aim of this study was to employ Lempel-Ziv complexity (LZC) to analyze the time series resulting from the blocking and unblocking process of ionic current through α-hemolysin (α-HL) nanopores induced by polyethylene glycol (PEG). The experimental system consisted in a planar lipid bilayer built by apposition of two monomolecular lipid films in a hole within a polytetrafluoroethylene (Teflon ® ) partition, which separates two identical compartments of a Teflon experimental chamber containing electrolyte solutions. The α-HL was added in the chamber, as well as PEG in two different concentrations, a lower concentration (400 µM) and a higher concentration (1000 µM). Potentials of + 20 to + 100 mV were applied. LZC values, that reflects the dynamic of the process, were lower for concentration of 400 µM of PEG than in 1000 µM for all voltages applied in the nanopore. When the sequences of block and unblock of the α-HL nanopore in 400 µM of PEG were randomized, there was an increase in the LZC values in relation to the original sequences, for all electrical potentials. These results lead us to deduce that the activity of block and unblock of α-hemolysin nanopore is a complex phenomenon, disclosing the stochastic nature of this process.