Siddharth Shekar, Chen-Chi Chien, Andreas Hartel, Peijie Ong, Oliver B Clarke, Andrew Marks, Marija Drndic, and Kenneth L Shepard. Wavelet Denoising of High-Bandwidth Nanopore and Ion-Channel Signals. Nano Letters January 2, 2019, DOI: 10.1021/acs.nanolett8b04388.
Recent work has pushed the noise-limitedbandwidths of solid-state nanopore conductance recordings tomore than 5 MHz and of ion channel conductance recordingsto more than 500 kHz through the use of integratedcomplementary metal-oxide-semiconductor (CMOS) inte-grated circuits. Despite the spectral spread of the pulse-likesignals that characterize these recordings when a sinusoidalbasis is employed, Besselfilters are commonly used to denoisethese signals to acceptable signal-to-noise ratios (SNRs) at thecost of losing many of the faster temporal features. Here, wereport improvements to the SNR that can be achieved usingwavelet denoising instead of Besselfiltering. When combinedwith state-of-the-art high-bandwidth CMOS recording in-strumentation, we can reduce baseline noise levels by over a factor of 4 compared to a 2.5 MHz Besselfilter while retainingtransient properties in the signal comparable to thisfilter bandwidth. Similarly, for ion-channel recordings, we achieve atemporal response better than a 100 kHz Besselfilter with a noise level comparable to that achievable with a 25 kHz Besselfilter. Improvements in SNR can be used to achieve robust statistical analyses of these recordings, which may provide importantinsights into nanopore translocation dynamics and mechanisms of ion-channel function.