Water is the Key to Double Helix, not Hydrogen: Study
Researchers have now disproved the prevailing theory of how DNA binds itself in the signatory double helix. They found that it is not the hydrogen bonds that hold together the two sides of the hereditary material DNA as previously thought.
Instead, the scientists at the Chalmers University of Technology in Sweden found that water is the key to the DNA double helix.
The discovery is published in the journal PNAS. And this discovery opens doors for a new understanding of research in medicine and life sciences.
Our DNA is constructed of two strands consisting of sugar molecules and phosphate groups. And between these 2 strands are nitrogen bases, the compounds which make up organism’s genes, with hydrogen bonds between them.
Until this recent study, it was commonly thought that those hydrogen bonds were what held the two strands of DNA together.
However now, the scientists show that the secret to DNA’s helical structure may be that the molecules have a hydrophobic or water-repelling interior, in an environment consisting mainly of water.
The environment is therefore hydrophilic or water-attracting, while the DNA molecules’ nitrogen bases are hydrophobic or pushing away the
surrounding water.And when hydrophobic units are in a hydrophilic environment, these units group together, to minimize their exposure to the water, the scientists said.
The role of the hydrogen bonds appears to be more to do with sorting the DNA base pairs so that they link together in the correct sequence in the DNA structure, researchers said.
This recent discovery is crucial for understanding DNA’s relationship with its environment, according to the researchers.
Bobo Feng, one of the scientists behind the study, said that the cells want to protect their DNA, and not expose its DNA to hydrophobic environments, which can sometimes contain harmful molecules. But at the same time, these cells’ DNA needs to open up in order to be used. Feng added.
The team believes that the cell keeps its DNA in a water solution most of the time and when a cell wants to do something with its DNA, say read, copy or repair it, cell exposes its DNA to a hydrophobic environment, said Feng.
For example, reproduction involves the base pairs dissolving from one another and opening up. The enzymes then copy both sides of the helix to create new DNA.
When it comes to repairing DNA, the damaged areas are subjected to a hydrophobic environment, to be replaced, researchers found.
A catalytic protein creates a hydrophobic environment. And this type of protein is central to all DNA repairs, meaning it could be the key to fighting many serious sicknesses, they said.
Understanding proteins could yield many new insights into how we could fight resistant bacteria, or potentially even cure cancer, the researchers noted.
Bacteria use a protein called RecA in order to repair their DNA, and the scientists believe their results could provide new insights into how this process works by potentially offering methods for stopping it and thereby killing the bacteria.
In human cells, the protein called Rad51 repairs DNA. This protein fixes mutated DNA sequences which otherwise could lead to cancer.
Feng said that in order to understand cancer, we need to understand how DNA repair occurs. To understand that, firstly we need to understand DNA itself. And So far, we have not understood DNA Properly, because we believed that hydrogen bonds were what held it together. Now, the researchers’ team have shown that instead, it is the hydrophobic forces which lie behind it. They have also shown that DNA behaves totally differently in a hydrophobic environment, Feng said.
The scientists studied how DNA behaves in a hydrophobic environment, a method they were the first to experiment with.
They used the hydrophobic solution polyethylene glycol (PEG). Step-by-step, they changed the DNA’s surroundings from the naturally hydrophilic environment into a hydrophobic one. Researchers aimed to discover if there is a limit where DNA starts to lose its structure when it does not have a reason to bind because the environment is no longer hydrophilic. The team observed that when the solution reached the borderline between hydrophilic and hydrophobic and the DNA molecules’ in their characteristic spiral form started to unravel.
Upon closer inspection, researchers observed that when the base pairs split from one another, holes are formed in the DNA structure, allowing water to leak in. And because DNA wants to keep it’s interior dry, it presses together, with the base pairs coming together again to squeeze out the water. In case of a hydrophobic environment, this water is missing, so the holes stay in place.
This discovery which proves water is the key to the double helix helps us to understand DNA, and how it repairs. And nobody has previously placed DNA in a hydrophobic environment like this and studied how it behaves, so it is not surprising that nobody has discovered this until now, he added.
