Enhanced Signal to Noise Ratio Enables High Bandwidth Nanopore Recordings and Molecular Weight Profiling of Proteins.

Abstract

Fast protein translocations often lead to bandwidth-limited amplitude-attenuated event signatures. In this study, we developed a protein- and electrolyte chemistry-centric pathway to construct a readily executable decision tree for the detection of non-attenuated protein translocations using conventional electronics. Each optimization encompasses increasing capture rate (CR), signal-to-noise ratio (SNR), and minimizing irreversible analyte clogging to collect >104 events/pipette spanning a host of electric fields. This was demonstrated using 11 proteins ranging from ∼12 kDa to ∼720 kDa. Moreover, both symmetric and asymmetric electrolyte conditions (cis and trans chamber electrolyte concentration ratios <> 1) were explored. As a result, asymmetric electrolyte conditions were favorable on the extreme ends of the size spectrum (i.e., larger, and smaller proteins) and while the remainder of proteins were best sensed under symmetric electrolyte conditions. Under these optimal conditions, only ≲10% of events were attenuated at 500 mV (≲ 5% for most proteins at 500 mV with only ≲1-5% of the population faster than ∼7 μs, which is the theoretical attenuation threshold for 100 kHz bandwidth). Finally, applied voltage (Vapp), peak current drop (ΔIp), electrolyte conductivity (K), and open-pore conductance (G0) were used to generate a linear relationship to evaluate the molecular weight of the protein (Mw) using plots of (dΔIp)/(dVapp) vs Mw/(G0/K).