NEW YORK (GenomeWeb) – Two recent studies have determined that proteins can be preserved in fossilized samples for far longer than previously thought possible.
Working independently, groups led by researchers at North Carolina State University and Taiwan's National Central University have found collagen peptides in dinosaur remains believed to be 80 million and 195 million years old, respectively. In the latter case, the findings push back by more than 100 million years the length of time over which protein has been found to be preserved.
In a study published last week in the Journal of Proteome Research, a team led by NC State paleontologist Mary Schweitzer identified eight peptides from collagen I in a Brachylophosaurus canadensis specimen that is approximately 80 million years old.
The study — which relied on a mass spec analysis led by Northwestern University professor Neil Kelleher using a Thermo Fisher Scientific 12T LTQ-Velos FT-ICR instrument — was a reanalysis of the Brachylophosaurus canadensis specimen, which Schweitzer and her colleagues initially investigated in 2009.
Using a different set of extraction, mass spec, and informatics approaches, the researchers expanded upon the peptides identified in the original study, detecting an additional six. They also identified two peptides that they detected in the original study, suggesting that these peptides are endogenous in origin, and not the result of contamination.
The study also indicates that previously studied specimens may benefit from reanalysis using the new protocols detailed in the JPR paper, the authors said, adding that they "obtained roughly the same amount of sequence data as the previous study with substantially less sample material."
Publishing their study this week in Nature Communications, the Taiwan-led team found evidence of collagen in a 195-million-year-old sauropodomorph, significantly expanding the duration over which protein is thought to be preserved.
Using in situ synchrotron radiation-based Fourier transform infrared spectrometry (SR-FTIR), the researchers identified the amides A, B, I, II, and III of collagen. They also detect the presence of haematite aggregates, which they said likely stemmed from hemoglobin "and other iron-rich proteins from the original blood."
These aggregates, "likely had a crucial role in the preservation of the [collagen] proteins," the authors wrote, suggesting that iron-containing hemoglobin and lactoferrin could have "played a key role as antioxidant for preventing further oxidation of [the identified] collagen."
Their findings suggest that, in the future, "enhanced methods are likely to lead to identification of the degradation components of collagen type I, and other organic remains across greater geologic timescales than previously considered possible."