An image of decanoic acid vesicles in salt water.
An image of decanoic acid vesicles in salt water.Photo by Courtesy photo
A major theory shared by scientists to explain the first spark of life on Earth has been given a new twist in a recent discovery by UW researchers.
The origins of life theory states that the earliest cells consisted of ribonucleic acid (RNA) inside of a vesicle, or bag-like structure, made of fatty acids. RNA carries the genetic information in all life forms. How it formed, however, remains a mystery.
“There are a lot of different, conflicting ideas about how life began,” said Matt Blosser, UW graduate student and co-lead researcher of the project. “Our findings suggest how the ingredients of RNA were brought to one place. This is the first step to creating a functional piece of RNA.”
Blosser said their findings suggest the first spark of life could also have formed in a salty environment such as the ocean. Most scientists previously believed RNA formed on locations such as mineral surfaces before being incorporated into vesicles.
Roy Black, UW affiliate professor and co-lead researcher, said the research started about five years ago when he was reading about the origins of life. He wondered if fatty acids might play a role in naturally congregating the chemical precursors of RNA in one place. These chemical components include the sugar molecule ribose, and a set of four nucleobases — nitrogen-containing compounds found within RNA.
Blosser said there are two groups of biochemists studying origins of life: Many look to simply create RNA, while others look to see if they can get RNA into vesicles and form vesicles stable enough to hold the RNA.
“The approach we took was, ‘How can we solve both of those problems at the same time and see if they could help solve each other?’” Blosser said.
The team’s major finding was that compounds of fatty acids bind RNA nucleobases, which make the vesicles more stable.
The group used a type of fatty acid called decanoic acid, which is composed of a string of 10 carbons with a simple acid at the end. Decanoic acid has been found in significant quantities in meteorites, meaning it was likely present on Earth’s surface before life began.
To determine whether nucleobases bind to fatty acid aggregates, Black and Blosser used a filtration technique. The filter has small holes that allow individual molecules to pass through while retaining all the fatty acid aggregates. They added a base substance to the solution containing the aggregates and measured how much base stayed on each side of the filter.
In a separate method, they were able to determine the stability of the vesicles in salt water by testing the cloudiness of their solutions.
Salt disrupts fatty acid vesicles by causing them to clump together into clusters called flocs, instead of remaining as single bags.
In addition, the scientists also looked at each solution through a microscope to see if the vesicles were present as individual bags or clumps.
“When vesicles become unstable, it makes the solution appear cloudy, so we measured the cloudiness, or optical absorbance of the two solutions as they are cooling down from a high temperature,” Blosser said.
The group found that fatty acid solutions containing nucleobases were clearer, meaning individual vesicles were stable. In other words, the same bases of RNA that stuck to the fatty acid also protected the vesicles from the disruptive effects of salty water.
To the researchers’ surprise, they found the same result for the sugar molecule ribose. Blosser said the less cloudy the sugary aggregate solution, compared to the non-sugary solution, the greater the stability. When the researchers tested other types of sugar molecules such as glucose or xylose, they found that ribose still makes a more stable vesicle.
With their research work published online July 29 in the journal Proceedings of the National Academy of Sciences, Black was pleased with what the group accomplished.
“We still haven’t solved the whole problem,” Black said. “But we think it’s a major contribution to show at least how the pieces of RNA could come together, concentrate it, and orient it in a way where they could go on and form RNA.”
UW chemistry professor Sarah Keller provided the lab for the research and co-authored the paper with Black and Blosser. She was grateful for Black’s contributions to the research as an affiliate professor.
“Sometimes people contribute money, sometimes they contribute things, and in this case Roy contributed something very valuable to him and to my lab, namely his time,” Keller said. “On top of that, much of Roy’s research was self-funded. One of the many reasons that UW is great is because of people like him.”
Keller also added that this research illustrates the collegial and nimble nature of the UW science community.
“A visitor to UW might not realize that inside our solid, grand, traditional brick buildings are researchers who are metaphorically sprinting every day, light on their feet, toward the next discovery,” Keller said.
Reach reporter KJ Hiramoto at firstname.lastname@example.org. Twitter: @HiramotoJr
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