Measuring a frequency spectrum for single-molecule interactions with a confined nanopore

Area of Science:

• Biophysics
• Analytical Chemistry
• Single-molecule analysis

Background:

• Nanopore analysis offers insights into single molecule characteristics like volume and charge.
• Extracting dynamic information from complex nanopore current traces remains challenging.

Purpose of the Study:

• To present a novel nanopore analysis method using Hilbert-Huang Transform (HHT).
• To study vibrational features and interactions of single molecules during translocation.
• To demonstrate the method's applicability using aerolysin nanopores and poly(dA)4.

Main Methods:

• Employed Hilbert-Huang Transform (HHT) for analyzing nonlinear and non-stationary nanopore data.
• Measured frequency response of wild-type (WT) and mutant K238E aerolysin nanopores.
• Analyzed energy-frequency-time distribution spectra of ionic current recordings.

Main Results:

• Biological nanopores significantly influence high-frequency components (>2 kHz) of the current.
• Poly(dA)4 exhibited more consistent and confined interactions with K238E mutant than WT aerolysin.
• These interactions led to a prolonged translocation duration in the K238E mutant.

Conclusions:

• HHT provides a high-frequency resolution method for analyzing complex nanopore data.
• Frequency analysis characteristics can serve as a "single-molecule ionic spectrum".
• This spectrum encodes detailed information about weak single-molecule interactions within nanopores.