Scientists have discovered why the collagen in dinosaur skeletons has remained intact for millions of years, defying the usual 500-year lifespan of its chemical bonds.
By examining small-molecule mimics of collagen peptides, they revealed that interactions between the molecules’ acyl groups protect peptide bonds from hydrolysis by water, a finding that could inform the design of durable materials.
Dinosaurs continue to fascinate people, but that’s not their only enduring quality: Collagen in their skeletons remains intact for millions of years, despite containing chemical bonds that should only persist for about 500 years. Now, scientists report in the journal ACS Central Science that the unique tenacity of this protein may result from a molecular structure that shields these vulnerable bonds from attack by water that’s present in the environment.
Structural Secrets of Ancient Proteins
Collagen is the most abundant protein in animals. It’s found in skin and connective tissues, such as cartilage and bones. Fragments of collagen have been extracted from the bones of 68-million-year-old fossils of Tyrannosaurus rex and may have even been detected in the skeleton of a 195-million-year-old Lufengosaurus. Collagen consists of protein strands — chains of amino acids — that form triple helices.
Much like a rope, the helices in turn weave together to form a strong fibrous material. When exposed to water, the peptide bonds that connect amino acids normally break down in a process known as hydrolysis. But when peptides are incorporated in collagen, that destructive process doesn’t take place.
Various explanations have been proposed, but Ron Raines and colleagues felt those theories were missing a physical and chemical basis for the resistance of peptide bonds in collagen like that preserved in ancient dinosaur bones. The team set out to fill in the missing links.
Research Insights Into Collagen Durability
Using experimental and computational methods, the researchers examined the behavior of small-molecule mimics of collagen peptides. In particular, they studied the interactions between the molecules’ acyl groups, which each contain a carbon atom double bonded to an oxygen atom.
They found that each acyl group partially shares its electrons with a neighboring acyl group. These results suggest that such interactions protect every peptide bond in a collagen triple helix from hydrolysis, and therefore the structure is able to stay intact.
The researchers say lessons from the stability conferred by these interactions could help guide the design of other exceptionally long-lived materials.
Reference: “Pauli Exclusion by n→π* Interactions: Implications for Paleobiology” 4 September 2024, ACS Central Science.
DOI: 10.1021/acscentsci.4c00971
The authors acknowledge funding from the National Institutes of Health.
