Chemists at Oregon State University have pioneered a controversial theory about how supposedly-stable DNA bases can be pushed into a "dark state" in which they are highly vulnerable to damage from ultraviolet radiation – an idea that has challenged some of the most basic concepts of modern biochemistry.The findings could help explain how the presence of water was the key to the evolution of life on Earth, making it possible for life to emerge from what was once a hostile and unforgiving primordial soup of chemicals and radiation.
A study proving the existence of this "dark state" was published by OSU researchers in the Journal of Physical Chemistry – even though other journals had repeatedly rejected the findings because they were too radical. But studies at OSU, which were done with highly sophisticated electron spectroscopy, showed that the alleged stability of the nucleic acid bases in DNA is largely a myth.
"In their biological form, surrounded by other hydrogen-bonded bases, it's true that the nucleic acids which make up DNA are stable," Kong said. "But we found that living things, in their totality, provide an environment which creates that stability, through attachments within base pairs and/or with neighboring bases. These attachments allow damaging photonic energy to be released as heat. But a DNA base as an isolated molecule, just by itself, does not have that stability."
In a compelling experiment, OSU scientists probed the fate of nucleic acid bases after laser irradiation in the ultraviolet range. They found that the molecules – which react extraordinarily fast to ultraviolet light insults – could by themselves spend 20-300 nanoseconds in an unstable, vibrating "dark state" in which they could easily mutate and not fully recover from photonic damage.
"When the bases of DNA were first being formed billions of years ago, the atmosphere was actually quite hostile," Kong said. "It was a period prior to any protective ozone layer on Earth and the ultraviolet radiation was very strong. So if primordial DNA bases were forced into this vulnerable dark state, they should have incurred large amounts of photochemical damage that would have made the very survival of these bases difficult, let alone further evolution of life."
Except for one other finding, that is:
According to OSU research, the "dark state" essentially disappears in the presence of water. So if water were present, the earliest DNA bases would have been able to survive and eventually help form the basis for ever-more-complex life forms.
"What this is really telling us is that life is a unified process," Kong said. "It's not just a group of DNA bases, but it's also the physical environment in which they exist. Later on, as life became more evolved, there were other ways to achieve genetic stability. But at first, it simply may not have been possible without water."