Quantum Tunneling Makes DNA More Unstable

Many biologists assume that bizarre quantum phenomena play a relatively negligible role in the cell. However, a recent theoretical analysis of the chemical bonds that hold DNA together suggests that these effects may be much more common than once thought — acting as a major source of genetic mutations.

Researchers led by Louie Slocombe of the University of Surrey in England focused on the molecular “bases” that make up the rungs that connect the double strands of DNA and the hydrogen bond, formed with a proton, that connects the two sides of these rungs. keeps together. Their theoretical model included the quantum effects that allow a proton bound to the base cytosine on one strand to spontaneously “tunnel” and join the guanine base on the other.

Such an altered base pair, known as a tautomer, can quickly jump back to its original arrangement. But if the proton doesn’t come back by the time the two DNA strands separate — the first step of DNA replication — the cytosine can bind to another base, adenine, instead of guanine. This unnatural coupling creates a mutation.

Scientists have known since the discovery of DNA structure in the 1950s that base pairs can theoretically produce tautomers. But they thought quantum tunneling would have little relevance as a mutation generator due to the extraordinarily short lifetimes of these physical states.

The researchers’ model reported in Communication Physics, suggests, however, that the quantum process occurs so frequently that there may be hundreds of thousands of tautomers present in a cell’s genome at any given time. So even if these structures are ephemeral, so many come into place so often that they become a potentially rich source of mutations. This model suggests that quantum mechanical instability “might play a much more important role in DNA mutation than has been suggested so far,” the authors write. The team wonders how specific repair mechanisms deal with such quantum errors, given that the predicted number of tautomers is thousands of times greater than the total number of mutations in each human generation.

This work could potentially “pave the way for investigating various quantum tunneling processes in DNA and the cell membrane that could be of fundamental importance in molecular biology,” said Gizem Çelebi Torabfam, a scientist at Sabancı University Nanotechnology Research and Application Center in Istanbul. , who has studied quantum tunneling, but was not involved in this work. “We also need to consider ultra-fast transfer between two DNA bases in the pathogenesis of common diseases.”