Examining noise sources at the single-molecule level: 1/f noise of an openmaltoporin channel

We have studied the phenomenological origin of 1/f noise in a solute-specif ic bacterial inn 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 ex hibits noise that is "white" below 100 Hz. Combined with results of a recen t noise study of several bacterial porins, our observations suggest that 1/ f noise is caused by the equilibrium conductance fluctuations related to th e conformational flexibility of the channel pore structural constituents.