Examining Noise Sources at the Single-Molecule Level:1/fNoise of an Open Maltoporin Channel

We have studied the phenomenological origin of $1/f$ noise in a solute-specific bacterial ion channel, maltoporin. We show that after excision of small, but resolvable stepwise changes in the recordings of the current through a single open channel, the $1/f$ noise component disappears and the channel exhibits noise that is “white” below 100 Hz. Combined with results of a recent noise study of several bacterial porins, our observations suggest that $1/f$ noise is caused by the equilibrium conductance fluctuations related to the conformational flexibility of the channel pore structural constituents.