Pore-forming proteins are widespread across living organisms. In humans, they are essential for immune defense, while in bacteria they often act as toxins that puncture cell membranes. These microscopic pores allow ions and molecules to move through membranes, controlling molecular traffic within cells. Because of their precision and control, scientists have adapted them as nanopore tools for biotechnology, such as in DNA sequencing and molecular sensing.
Although biological nanopores have revolutionized biotechnology, they can behave in complex and sometimes erratic ways. Researchers still lack a complete understanding of how ions travel through them or why ion flow occasionally stops altogether.
Two particularly puzzling behaviors have long intrigued scientists: rectification and gating. Rectification occurs when the flow of ions changes depending on the “sign” (plus or minus — positive or negative) of the voltage applied. Gating happens when the ion flow suddenly decreases or stops. These effects, especially gating, can disrupt nanopore-based sensing and have remained difficult to explain.
A research team led by Matteo Dal Peraro and Aleksandra Radenovic at EPFL has now identified the physical mechanisms behind these two effects. Using a combination of experiments, simulations, and theoretical modeling, they found that both rectification and gating arise from the nanopore’s own electrical charges and the way those charges interact with the ions moving through the pore.
Experimenting With Electric Charges
The team studied aerolysin, a bacterial pore commonly used in sensing research. They modified the charged amino acids lining its interior to create 26 nanopore variants, each with a distinct charge pattern. By observing how ions traveled through these modified pores under different conditions, they were able to isolate key electrical and structural factors.
To better understand how these effects evolve over time, the scientists applied alternating voltage signals to the nanopores. This approach allowed them to distinguish rectification, which occurs quickly, from gating, which develops more slowly. They then built biophysical models to interpret their data and reveal the mechanisms at work.
How Nanopores Learn Like the Brain
The researchers discovered that rectification happens because of how the charges along the inner surface influence ion movement, making it easier for ions to flow in one direction than the other, similar to a one-way valve. Gating, in contrast, occurs when a heavy ion flow disrupts the charge balance and destabilizes the pore’s structure. This temporary collapse blocks ion passage until the system resets.
Both effects depend on the exact placement and type of electrical charge within the nanopore. By reversing the charge “sign,” the team could control when and how gating occurred. When they increased the pore’s rigidity, gating stopped completely, confirming that structural flexibility is key to this phenomenon.
Toward Smarter Nanopores
These findings open new possibilities for engineering biological nanopores with custom properties. Scientists can now design pores that minimize unwanted gating for applications in nanopore sensing, or deliberately use gating for bio-inspired computing. In one demonstration, the team created a nanopore that mimics synaptic plasticity, “learning” from voltage pulses much like a neural synapse. This discovery suggests that future ion-based processors could one day harness such molecular “learning” to power new forms of computing.
