Paleoproteomics Opens a Window into the Past

[Judi Lynn]

Researchers are looking to proteins to explore the biology of ancient organisms, from medieval humans all the way back to dinosaurs.

By Catherine Offord | March 1, 2018

Elena Schroeter is accustomed to being economical with her samples. A postdoctoral researcher at North Carolina State University, Schroeter analyzes pieces of ancient bone that have been preserved in the ground for millions of years—and in doing so, destroys them. So her collaborators rarely give her more than a gram or two of material to work with. “People don’t want you to grind up their dinosaurs,” she explains. “You have to learn how to do a lot with a little.”

But even just a pinch of dinosaur bone dust could help reveal the ancient animal’s secrets. In one recent project, for example, Schroeter and her advisor Mary Schweitzer extracted and analyzed collagen peptides from just 200 mg of an 80-million-year-old fossil of a Cretaceous-era herbivore, Brachylophosaurus canadensis, excavated in Montana. The amino acid sequences of those peptides, published last year, placed the dinosaur on a branch of the phylogenetic tree between crocodiles and basal birds such as ostriches.1 What’s more, the team’s collection of analyzable peptides from the ancient specimen suggests that there might be other fossils out there with similar molecular information hidden in them.

Although the findings were controversial—some researchers still doubt that proteins can resist degradation for tens of millions of years—Schroeter is one of a small but growing number of researchers specializing in the analysis of ancient proteins, or paleoproteomics, to learn about the biology of organisms past. It’s been a goal of scientists for some time now; in the 1950s, several researchers were already discussing the possibility of studying peptides preserved in fossils. But only in the last two decades have advances in techniques for protein analysis, such as mass spectrometry, made the feat practical.

The potential for learning about ancient life from paleoproteomics is substantial. Via their amino acid sequences, peptides offer many of the same insights as DNA about genomic makeup—information that can support new or existing phylogenetic trees, inform research on past migrations, and assist with species identifications, even amidst a jumble of ancient remains. (See “What’s Old Is New Again,” The Scientist, June 2015.) But proteins tend to last longer in the geological record than nucleic acids, thanks to both greater volumes at deposition and more-degradation-proof molecular structures. “Both DNA and proteins are chains of building blocks,” explains Enrico Cappellini, a paleoproteomics researcher at the Natural History Museum of Denmark. “But the bonds connecting those blocks are more stable in proteins than in DNA.” The oldest confirmed DNA samples, extracted from ice cores taken in southern Greenland, are less than 800,000 years old, while the oldest protein, even by conservative estimates, dates back several million years.

More:
https://www.the-scientist.com/?articles.view/articleNo/51913/title/Paleoproteomics-Opens-a-Window-into-the-Past/