A Fundamental DNA Assumption Just Collapsed—and Nanopore Science Is Rewriting the Rules

DNA in Nanopores: Why “Noisy” Signals Were Misread for Decades

Nanopore Experiments Got DNA Wrong for Years. This discovery changes everything.

A new summary of research is changing a long-held belief in nanopore studies: the “messy” ionic-current signals that many labs thought showed DNA knots are usually something different. The update is important because nanopore sensing, which is used for sequencing, molecular diagnostics, or polymer physics, depends on a careful assumption: that the electrical signal truly reflects what the molecule is doing.

This new work asserts that the signal has been providing accurate information all along, albeit not in the way researchers initially believed.

Early hints of the correction have been in the literature for years. What feels new now is the claim’s scope: this is not a small parameter tweak. It is a mechanism shift, with downstream consequences for how experiments are designed, how anomalous events are filtered, and what “unexpected” readouts should trigger follow-up rather than dismissal.

The story turns on whether nanopores are merely measuring DNA conformations—or actively creating them during translocation.

Key Points

• New research shows that electrical signals once thought to be caused by DNA knots during nanopore translocation are often actually due to plectonemes—twisted coils—rather

• The mechanism is not simply that "DNA is complicated." It is torsion: fluid/ion-driven forces inside the pore can rotate DNA, accumulate torque, and drive coiling outside the pore.

• This reframes many “irregular” or “multi-level” events as instrument-coupled physics, not rare sample artifacts.

• Practical impact: we may need to change how we classify events, set filtering limits, and create calibration methods—especially in solid-state nanopore research and any process that analyzes

• The work also points to an opportunity: controlling twist propagation (for example, via designed nicks) can suppress coil formation, suggesting new experimental controls and possibly new sensing modes for DNA integrity.

• For sequencing ecosystems, the impact is less about rewriting base calling overnight and more about improving how labs interpret and manage anomalous signals—because what gets called “noise” often drives error modes and bias.

Background

Nanopores are tiny holes in a membrane that let ions flow under an applied voltage. When DNA enters the pore, it partially blocks the ionic current. That blockade becomes the measurement: a time series that reflects how the molecule moves and what occupies the pore at each moment.

In many nanopore experiments, especially those looking at double-stranded DNA (dsDNA) moving through solid-state pores, researchers have often seen “tangled” signals: long interruptions, multiple blockages, and uneven patterns that don’t look like a

A common interpretation—almost a folk model across subfields—was that these complex traces indicated knots. The intuition was straightforward: when a long string is pulled through a narrow hole, it occasionally snags. The current trace becomes the snag report.

The new work challenges the default diagnosis. It argues that many events blamed on knots are instead plectonemes: sections of DNA that twist and coil around themselves like a phone cord, produced by torque rather than by pre-existing topological tangling.

Analysis

The Old Model: “Messy Signal = Knot (or Tangling)”

The historical model treated complex blockade events as primarily conformation reporting:

• DNA in solution forms an ensemble of configurations.

• Occasionally, it contains a knot or tight entanglement.

• As that structure approaches and passes through the pore, it produces an abnormal current signature—often longer-lasting and more complex than a standard event.

• Therefore, irregular traces were used as a proxy for knot frequency, knot type, or polymer topology under confinement.

This model was attractive because it made nanopores feel like a passive microscope: the pore “reads out” whatever structure the molecule already had.

The New Finding: The Pore Can Generate Twist-Driven Coils

The revised mechanism is more active. In this framing, the nanopore is not merely an observer; it is a mechanical actuator.

As DNA is pulled through with voltage, the movement of the fluid and electrical effects in the small space can cause the DNA to spin inside the pore. That rotation transmits torsional stress along the molecule. If a twist can move away from the pore, it can build up and form plectonemes—coiled shapes that can last while moving and create a unique electrical signal.

Two key practical distinctions emerge:

• Knots are topological entanglements. Under tension, they tend to tighten and can pass through relatively quickly once mobilized.

• Plectonemes are torsional coils. They can grow, persist, and create longer-duration signatures because the driving force is ongoing torque generation coupled to the pulling force.

That is why a decades-old visual heuristic—“longer, messier equals knottier”—can fail. Duration and complexity are not just reporting topology; they may be reporting torsion dynamics.

Why This Looks Like a “Textbook Correction”

This is not merely renaming a phenomenon. It changes what the signal is evidence of.

If a large slice of irregular events are plectonemes, then:

• Past conclusions about knot prevalence inferred from current traces may be inflated or mischaracterized.

• Comparisons across pore geometries, voltages, and salt conditions become riskier because those parameters can change how much torque is generated, not just how easily pre-existing knots pass.

• “Too many tangled events to be equilibrium knots” stops being a mystery and becomes a diagnostic: the experiment may be driving the system into a non-equilibrium torsional regime.

In other words, the correction is epistemic: it changes what counts as proof.

Practical Downstream Consequences for Sequencing Accuracy

For common nanopore sequencing (where motor enzymes pull single-stranded DNA through tiny biological openings), the immediate effect is not expected to be a significant increase in accuracy just from changing the name of knots to plectonemes. Factors such as k-mer context ambiguity, pore chemistry, motor kinetics, and model training limits dominate modern basecalling errors.

But there are still real accuracy-adjacent consequences:

1. Anomaly handling and read filtering
   Many pipelines discard or down-weight reads with abnormal signal segments. If those segments are often torsion-driven structures, then “bad read” may actually mean “physics regime change.” Better classification could reduce unnecessary discard rates or help segregate reads that need different model treatment.

2. Interpretation of long-fragment behavior
   Ultra-long DNA and translocation-based assays can show extended disruptions. If those are plectonemes, not knots, the appropriate mitigation may be changing voltage, salt, pore surface charge, or rotational constraints—not just improving sample prep.

3. Event segmentation and dwell-time assumptions
   Some models assume that unusually long dwell times correspond to rare tangles. If long events are caused by torque and depend on conditions, the rules set for one situation might not work well in another, which can lead to more mistakes.

4. Damage and integrity sensing as a feature, not a bug
   The work highlights that blocking twist propagation (for example, using designed nicks) can strongly suppress plectoneme signatures. This means that nanopore signals could be adjusted to better detect DNA integrity, strand continuity, or twisting issues, which could lead to new ways of diagnosing problems.

What Most Coverage Misses

The hinge is that nanopore “noise” is often interaction noise, not measurement noise.

The way the pore's electric field and the fluid flow inside it can twist a helical polymer, forming lasting shapes that look like existing tangles. That shifts incentives in experimental design: instead of only optimizing for signal-to-noise electronics, researchers may need to treat nanopores as active mechanical environments and design controls that isolate whether the pore is creating the phenomenon.

What would confirm it in the coming weeks:

• Labs reproduce the same “tangled” signatures while systematically varying conditions that affect torque generation (voltage, ionic strength, pore surface properties) and observe predictable shifts in event duration distributions.

• Independent groups show that altering rotational constraints or twist propagation (for example, by introducing controlled nicks or using torsionally relaxed constructs) reliably suppresses the long-duration signatures without changing DNA length or concentration.

What Changes Now

The short-term change is conceptual but operational:

• Researchers interpreting complex ionic-current traces should treat “knot” as a hypothesis, not a default label, because the same signature family can arise from twist-driven plectonemes.

• When trying to understand electrical signals to figure out the shape of polymers, it might be necessary to include specific controls for twisting, or at least check how sensitive the setup is to twisting

• Data pipelines might improve if we sort long, unusual events by how long they last and the situation they occur in, since the way they happen suggests different ways to

The main consequence is simple: classification improves because the mechanism is clearer—because the pore is not neutral.

Longer-term (months to years), this can change what nanopores are used for. If we can predict and control how plectonemes form, nanopores can do more than just read DNA sequences or check if something is there; they can also be adjusted to study DNA's physical properties, stability, and twisting state—information that many other

Real-World Impact

A genomics lab running nanopore-based assays notices a recurring class of long “junk events” that tank throughput. Under the old model, they blame sample contamination or knotty fragments and spend weeks tweaking extraction. Under the new model, they test voltage and salt regimes and watch the events collapse—because the pore was driving torque.

A device team building a solid-state nanopore diagnostic sensor sees inconsistent detection of long DNA targets. They stop ignoring the unusual signals and change the surfaces of the pores and the solutions used to lessen the twisting effect, improving performance without altering the electronics.

A research group studying DNA topology uses nanopores to estimate knot frequency in polymers. They re-run key controls with torsion-blocking constructs. Their inferred knot rates shift—prompting a correction in conclusions about how often knots form at equilibrium under their conditions.

A biotech exploring “DNA damage signatures” realizes that torsion sensitivity is a signal channel. They create tests where the presence of strand nicks reduces the signals related to plectonemes—transforming a previous problem into useful