We have not quite entered Jurassic Park, but researchers have successfully extracted protein from a 68 million year old Tyrannosaurus rex bone. Mary Higby Schweitzer of North Carolina State University, and her colleagues at Harvard Medical School and Beth Israel Deaconess Medical Center, have identified the protein collagen in soft tissue recovered from a fossil dinosaur bone and found it to be remarkably similar to that of modern chicken collagen. Their findings could change our view of fossil formation and preservation and provide evidence that supports the link between dinosaurs and modern birds.
Schweitzer originally extracted soft tissue from a fossil T-rex bone found in the Hell Creek formation in Montana. She demineralized it and was surprised to find a soft tissue matrix. She then carried out an analysis using electron and atomic force microscopy examination to see if she could identify the banding patterns characteristic of collagen. She and her colleagues then tested the samples against various antibodies known to react with collagen and discovered the telltale signs of organic matter—the protein collagen; something that conventional wisdom says should not survive the fossilization process.
Surprised by this finding, Schweitzer then turned to mass spectrometry expert John Asara of the Beth Israel Deaconess Medical Center and Lewis Cantley to obtain definitive evidence for protein. In this second study, which also looked at fossilized mastodon remains, the researchers carried out a sophisticated mass spectrometric analysis to reveal the amino acid sequence present in collagen and so obtain the sequence of a 68 million-year-old protein.
"We looked for collagen because it's plentiful, it's durable, and it has been recovered from other fossil materials, although none as old as this T-rex," Schweitzer says. "It's also a relatively easy molecule to identify, and it's not something that any microbes living in the immediate environment could produce," she adds. Identifying collagen in the soft tissue indicates that it is original T-rex protein.
The researchers have now compared the collagen sequences from the T-rex bone and found there to be similarities with protein sequences obtained from modern chickens, frogs, and newts. "The similarity to chicken is definitely what we would expect given the relationship between modern birds and dinosaurs," Schweitzer says.
The new data will help scientists learn more about the evolutionary relationships of the dinosaurs and modern birds, about how preservation happens, and about how molecules degrade over time. The researchers suspect that the proteins were preserved by the presence of rogue free radicals that made them bind to other molecules, preventing fossilization from destroying them.
Science, 2007, 316, in press; http://dx.doi.org/10.1126/science.1138709
Science, 2007, 316, in press; http://dx.doi.org/10.1126/science.1137614