There may be another force, even stronger than the hydrogen bond that holds our DNA together, new research suggests.
First discovered in the 1950s, the double helix structure of our genetic material has become emblematic, even though we are still figuring out how all of its pieces fit together.
Looking like a twisted ladder, the columns are nitrogen pairs of bases held together by some of the strongest intermolecular attractions out there: hydrogen bonds.
Linking the two sides of the ladder, these ultra-strong bonds are often described as a major stabilizing force in DNA. But there may be another, more important factor in the game
of DNA replication usually occurs with the help of several enzymes that "break" DNA molecules by breaking their hydrogen bonds. However, this is not the only way to destabilize the double helix.
By testing DNA in a more hydrophobic environment than normal, researchers at the Chalmer University of Technology in Sweden have shown for the first time that this water-repulsive force is sufficient to unleash a double helix by itself.
"The primary stabilizer of the DNA double helix is not the hydrogen bonds at the base of the pair, but the arrangement of base-pile coins," conclude the authors, "whose hydrophobic approximation, which requires abundant water, indirectly renders the interior of DNA dry. so that hydrogen bonds can exert full recognition power. "
In other words, since DNA base pairs are naturally repulsive in water, in a normal aqueous solution, they are arranged together to stay safe from their environment ̵
clearly that enzymes in nature are doing something similar, but given other similar models, the team believes this is a separate possibility.
Separating these groups requires the opposite effect, by gradually adding a hydrophobic solution of polyethylene glycol – often used in cars like antifreeze – eki The DNA has shown that DNA loses its structure and this happens properly because the environment passes from water-loving to repelling water.
"Cells want to protect their DNA and not expose it to hydrophobic media, which can sometimes contains harmful molecules, "explains chemical engineer and lead author Bobo Feng.
" But at the same time, the DNA of the cells must open upwards in order to be used. "
As such, Feng and his colleagues propose that a normal cell holds DNA in aqueous solution until it wants to read, copy, or repair its DNA. Only then does the cell create a more hydrophobic environment by using enzymes with a similar polyethylene function glycol.
Stephen Brenner, a molecular biophysicist at NASA, told ScienceAlert that this was important demonstrating a new way in which enzymes can "melt" double strands of DNA for transcription or repair However, he warns that the manner in which many media outlets have covered this document is not completely accurate.
However, many report, he says that the results do not suggest that hydrogen bonds are unimportant for the formation of DNA: These hydrophobic forces alone play a crucial role.
And this is hardly a new concept. Models that include hydrophobic interactions in the double helix date back to at least the 90s of the last century and there are entire laboratories today, dedicated to this path of exploration.
As early as 1997, scientists began to question the notion that hydrogen bonds alone could hold the two strands of DNA double-stranded together. This textbook explanation seemed to be insufficient and a few years later, in 2004, a study found that a hydrogen bond was not necessary for base pair stability.
Just a few years ago, in 2017, a study found that the lack of complementary hydrogen bonds did not really bother the cells and that the synthetic bases were somehow successfully transcribed and translated using only hydrophobic forces.
Together, these results suggest that perhaps the forces we have observed in nature are not the only ones responsible for the double helix.
"It would be very easy to say that additional hydrogen bonds are what determines DNA and RNA," says biochemist Floyd Romesberg, author of the 2017 paper.
"But we have found that other than the hydrogen bond, they can participate productively in every step of storing and retrieving information. "
Yet, as we have learned over the years, there are still limitations to the conclusions that models can draw from them.  "One of the sad lessons of physical organic chemistry of the last century," Benner tells ScienceAlert, "is that the effort to separately model the behavior of molecules as a result of various factors .. tells you more about the chemist who does modeling. than it tells you about the molecules themselves. "
These frameworks, for example, can be judged by their ability to simply explain DNA or by their ability to actually make it personally, Benner thinks. that the latter analysis is more objective because of the explanations per se and can often just to convince us that we understand what is happening.
"If, however, our models actually allow us to do things, then they really must have some reality behind them," he argues.
Ultimately, Benner says that both the hydrogen bond and the hydrophobicity have proven necessary for the production of natural DNA, and this double-stranded model is currently being used in both human medicine and NASA's quest for extraterrestrial life.
The new study adds to this idea by providing a possible biological mechanism for this process.
"No one before has put DNA in a hydrophobic environment like this and studied how it behaves, so it's not surprising that no one has found it so far, "Feng says.
The results are published in PNAS .