The DNA is maintained by hydrophobic forces

Researchers at Chalmers University of Technology in Sweden have refuted the current theory of how DNA binds. As is generally believed, it is not hydrogen bonds that bind the two sides of the DNA structure together. Instead, water is the key. This discovery paves the way for new research knowledge in medicine and life sciences. The results are published in PNAS.

DNA consists of two strands consisting of sugar molecules and phosphate groups. Between these two strands are nitrogenous bases, the compounds that make up the genes, with hydrogen bonds between them. Until now, it was generally thought that these hydrogen bonds held the two strands together.

But now, researchers at the Chalmers University of Technology have shown that the secret of the helical structure of DNA lies perhaps in the fact that the molecules have a hydrophobic interior, in an environment consisting primarily of d & # 39; water. The environment is therefore hydrophilic, while the nitrogenous bases of the DNA molecules are hydrophobic, repelling the surrounding waters. When the hydrophobic units are in a hydrophilic environment, they group together to minimize their exposure to water.

The role of hydrogen bonds, previously considered essential for maintaining DNA helices together, seems to be more related to sorting the base pairs so that they bind in the right order. The discovery is crucial to understand the relationship of DNA with its environment.

"The cells want to protect their DNA and not expose it to hydrophobic environments, which can sometimes contain harmful molecules," said Bobo Feng, one of the researchers behind the company's ## 147 ## 39; study. "But at the same time, the cell's DNA must open to be able to be used."

"We think that the cell retains its DNA in an aqueous solution most of the time, but as soon as a cell wants to do something with its DNA, like reading it, copying it or repairing it, it exposes it." DNA to a hydrophobic environment. "

Reproduction, for example, implies that the base pairs dissolve and open. The enzymes then copy both sides of the helix to create a new DNA. When it is a question of repairing the damaged DNA, the damaged areas are subjected to a hydrophobic environment, to be replaced. A catalytic protein creates the hydrophobic environment. This type of protein is at the heart of all DNA repairs, which means that it could be the key to fighting many serious diseases.

Understanding these proteins could provide a lot of new information on the fight against resistant bacteria, for example, or the potential treatment of cancer. The bacteria use a protein called RecA to repair their DNA, and the researchers believe that their findings could provide new insights into how this process works, potentially offering methods to stop and kill the bacteria.

In human cells, the Rad51 protein repairs the DNA and fixes the mutated DNA sequences, which might otherwise cause cancer. "To understand cancer, we need to understand how DNA is repaired.To understand it, we must first understand the DNA itself," said Bobo Feng. "Until now, we have not done so because we thought hydrogen bonds were what held him, and now we have shown that it is rather the hydrophobic forces that are hiding behind." It has also been shown that DNA behaves totally differently in a hydrophobic environment. This could help us understand DNA and its repair. Nobody had previously placed this DNA in a hydrophobic environment like this one or studied its behavior. It is not surprising that no one has discovered it so far. "

The researchers also studied the behavior of DNA in a more hydrophobic environment than normal, method with which they were the first to experiment. They used the hydrophobic solution of polyethylene glycol and gradually altered the environment of the DNA, which went from a naturally hydrophilic environment to a hydrophobic environment. They wanted to know if there is a limit to which DNA begins to lose its structure, while DNA has no reason to bind because the environment is no longer hydrophilic. The researchers observed that as the solution reached the boundary between hydrophilic and hydrophobic, the spiral shape characteristic of the DNA molecules began to crumble.

After a closer inspection, they found that when the base pairs separated from each other (due to external influences or simply random movements), holes formed in the structure, which allowed the Water to penetrate to the interior. Because DNA wants to keep his interior dry, he presses together, with the base pairs coming together again to bring out the water. In a hydrophobic environment, this water is missing, so the holes remain in place.

"Hydrophobic catalysis and the potential biological role of DNA de-stacking induced by effects on the environment" is published in Proceedings of the National Academy of Sciences (PNAS).