By Science Daily
Stanley Miller, the chemist whose landmark experiment published in 1953 showed how some of the molecules of life could have formed on a young Earth, left behind boxes of experimental samples that he never analyzed. The first-ever analysis of some of Miller’s old samples has revealed another way that important molecules could have formed on early Earth.
The study discovered a path from simple to complex compounds amid Earth’s prebiotic soup. More than 4 billion years ago, amino acids could have been attached together, forming peptides. These peptides ultimately may have led to the proteins and enzymes necessary for life’s biochemistry, as we know it.
In the new study, scientists analyzed samples from an experiment Miller performed in 1958. To the reaction flask, Miller added a chemical that at the time wasn’t widely thought to have been available on early Earth. The reaction had successfully formed peptides, the new study found. The new study also successfully replicated the experiment and explained why the reaction works.
“It was clear that the results from this old experiment weren’t some sort of artifact. They were real,” said Jeffrey Bada, distinguished professor of marine chemistry at the Scripps Institution of Oceanography at the UC San Diego. Bada was a former student and colleague of Miller’s.
The study was supported by the Center for Chemical Evolution at the Georgia Institute of Technology, which is jointly supported by the National Science Foundation and the NASA Astrobiology Program. The study was published online June 25 in the journalAngewandte Chemie International Edition. The work was primarily a collaboration between UC San Diego and the Georgia Institute of Technology in Atlanta. Eric Parker, the study’s lead author, was an undergraduate student in Bada’s laboratory and is now a graduate student at Georgia Tech.
Jeffrey Bada was Stanley Miller’s second graduate student. The two were close and collaborated throughout Miller’s career. After Miller suffered a severe stroke in 1999, Bada inherited boxes of experimental samples from Miller’s lab. While sorting through the boxes, Bada saw “electric discharge sample” in Miller’s handwriting on the outside of one box.
“I opened it up and inside were all these other little boxes,” Bada said. “I started looking at them, and realized they were from all his original experiments; the ones he did in 1953 that he wrote the famous paper in Science on, plus a whole assortment of others related to that. It’s something that should rightfully end up in the Smithsonian.”
The boxes of unanalyzed samples had been preserved and carefully marked, down to the page number where the experiment was described in Miller’s laboratory notebooks. The researchers verified that the contents of the box of samples were from an electric discharge experiment conducted with cyanamide in 1958 when Miller was at the Department of Biochemistry at the College of Physicians and Surgeons, Columbia University.
An electric discharge experiment simulates early Earth conditions using relatively simple starting materials. The reaction is ignited by a spark, simulating lightning, which was likely very common on the early Earth.