68-million-year-old collagen matches proteins in modern chickens
Palaeontologists and biochemists in the US have joined forces to identify proteins from a 68-million-year-old Tyrannosaurus Rex, showing that organic matter containing biological information can be preserved for enormous lengths of time under the right conditions. The research is helping to uncover new evolutionary links between dinosaurs and living species.
A team led by Mary Schweitzer at North Carolina State University in Raleigh, US, had discovered the T. Rex skeleton in 2003 under 1000 m3 of sandstone at the Hell Creek Formation in Montana, US. The process of fossilization usually replaces all organic matter with minerals, leaving only a stone ’copy’ of the original. But when the fossilized femur and tibia bones were (reluctantly) being broken up for transport, the scientists found ’fibrous and flexible soft tissues’ inside. Angela Milner, a palaeontologist at the Natural History Museum in London told Chemistry World, ’The bones were mummified without being completely fossilized - it is nice to recover the preserved proteins. Although most organic material like DNA will not last more than around 30,000 years, collagens are very robust - I have seen them in specimens up to 130-million-years-old.’
In a parallel study, a team led by John Asara at Beth Israel Deaconess Medical Center, Boston, US, analysed both the T. Rex samples and the bones of a 160,000-year-old extinct mastodon, an ancient relative of the elephant. They were using the latest ion-trap mass spectrometers, usually used to investigate human disease, to identify the amino acid building blocks of the ancient proteins.
Asara told Chemistry World: ’We managed to sequence seventy protein sequences from the mastodon and seven from the T. Rex.’ The scientists then compared the sequences with those found in modern day animals. ’The mastodon proteins matched living mammalian species like cows, elephants and dogs, whereas the T. Rex proteins matched chicken, newt and frog,’ said Asara. ’By looking at this we can find chemical evidence showing that species such as birds have evolved from dinosaurs.’
As spectrometry and purification techniques improve in accuracy, the team hopes to extract more proteins from ancient dinosaur bones and discover protein sequences that are unique to dinosaurs.