Topic: Biology

Researchers at the University of Cambridge have discovered a crucial process that shapes how DNA behaves as it moves through tiny pores. This finding could influence future advances in genomics and biosensing.

For many years, scientists believed that complex electrical patterns seen during experiments were caused by DNA forming knots. However, new research shows that this assumption was often wrong. Instead of forming true knots, DNA frequently twists around itself during nanopore translocation.

The study, published in Physical Review X, reveals that these twisted structures, known as plectonemes, resemble a coiled phone cord rather than a tied knot. This distinction matters because twists and knots affect electrical signals in very different ways.

To reach this conclusion, the researchers tested DNA using both glass and silicon nitride nanopores across a wide range of voltages and conditions. They noticed that so-called 'tangled' events, when more than one section of DNA occupied the pore at the same time, occurred far more often than knot theory could explain.

The team found that the twisting comes from electroosmotic flow, the movement of water driven by electric fields inside the nanopore. As water flows past the DNA, it applies a spinning force to the helical molecule. This torque travels along the strand, causing sections outside the pore to coil into plectonemes.

Computer simulations that applied realistic forces and torques confirmed this behavior and showed that plectoneme formation depends on DNA's ability to transmit twist along its length.

Why It Matters

This discovery could lead to more accurate analysis of genetic material, which is crucial in fields like medicine and forensic science. It also highlights the importance of understanding the fundamental processes involved in DNA sensing technologies.

Key Facts

• Scientists at the University of Cambridge have identified a crucial process that shapes how DNA behaves as it moves through nanoscale pores.
• The process involves DNA twisting around itself during nanopore translocation, forming structures called plectonemes.
• Plectonemes are different from true knots and affect electrical signals in distinct ways.
• Electroosmotic flow is the movement of water driven by electric fields inside the nanopore that causes DNA to twist.
• Computer simulations confirmed that plectoneme formation depends on DNA's ability to transmit twist along its length.

Key Terms

Plectonemes

Twisted structures formed when DNA twists around itself during nanopore translocation

Implications

This discovery could lead to more accurate analysis of genetic material, which is crucial in fields like medicine and forensic science. It also highlights the importance of understanding the fundamental processes involved in DNA sensing technologies.