As far as we know, DNA is the molecule of life. For a long time, it was believed that the two strands of genetic material were bound together by the bonds between hydrogen atoms in the structure. However, researchers in Sweden don’t think this is the case.
As reported in the journal PNAS, the team from Chalmers University of Technology argue that the molecules of DNA are hydrophobic (they are repelled by water), so when they are in a water-rich environment, like the interior of a cell, they are pushed together to minimize exposure to water. The hydrogen bonds still play a role, but the scientists believe they are involved in sequencing the base pairs rather than holding the two strands together.
The team used a solution of polyethylene glycol to slowly and gradually turn the DNA’s environment from naturally hydrophilic to hydrophobic. They saw that once the solution is equally hydrophilic and hydrophobic, the DNA molecules begin to unravel.
"Cells want to protect their DNA, and not expose it to hydrophobic environments, which can sometimes contain harmful molecules," Bobo Feng, one of the researchers behind the study, said in a statement. "But at the same time, the cells' DNA needs to open up in order to be used. We believe that the cell keeps its DNA in a water solution most of the time, but as soon as a cell wants to do something with its DNA, like read, copy, or repair it, it exposes the DNA to a hydrophobic environment."
It’s very early days for this research, but the findings hold promise for scientists in various labs. The DNA molecules separate for several reasons (such as reproduction and repair), so understanding how this happens could help scientists with their research. For example, such knowledge could be used to fight off antibiotic-resistant bacteria by affecting their DNA directly or to tackle cancer cells.
“To understand cancer, we need to understand how DNA repairs. To understand that, we first need to understand DNA itself," says Bobo Feng. "So far, we have not, because we believed that hydrogen bonds were what held it together. Now, we have shown that instead, it is the hydrophobic forces which lie behind it. We have also shown that DNA behaves totally differently in a hydrophobic environment. This could help us to understand DNA, and how it repairs.”