Iron preserves, hides ancient tissues in fossilized remains

Nov 26, 2013

New research from North Carolina State University shows that iron may play a role in preserving ancient tissues within dinosaur fossils, but also may hide them from detection. The finding could open the door to the recovery of more ancient tissues from within fossils.

Mary Schweitzer, an NC State paleontologist with a joint appointment at the N. C. Museum of Natural Sciences, first announced the surprising preservation of in a T. rex fossil in 2005. Her subsequent work identified proteins in the soft tissue that seemed to confirm that the tissue was indeed T. rex that had been preserved for millions of years. But the findings remained controversial in part because no one understood the chemical processes behind such preservation.

Schweitzer's latest research shows that the presence of hemoglobin – the -containing molecule that transports oxygen in red blood cells – may be the key to both preserving and concealing original ancient proteins within fossils. Her results appear in Proceedings of the Royal Society B.

"Iron is necessary for survival, but it's also highly reactive and destructive in living tissues, which is why our bodies have proteins that transport iron molecules to where they are needed but protect us from unwanted reactions at the same time," Schweitzer says. "When we die, that protective mechanism breaks down and the iron is turned loose on our tissues – and that destructive process can act in much the same way formaldehyde does to preserve the tissues and proteins."

Hemoglobin seems to be the key. Both birds and crocodiles, the dinosaur's closest living relatives, have large, nucleated red blood cells. Therefore they also have more hemoglobin per cell than mammals. If dinosaur blood cells were similar to either one of those species, which seems likely, then their would also contain much more hemoglobin than human cells, amplifying iron's preservative effect on the tissues. If the hemoglobin were contained in a bone in a sandstone environment, keeping it dry and insulated from microbes, preservation becomes more likely.

Schweitzer and her team noticed that iron particles are intimately associated with the soft tissues preserved in dinosaurs. But when they chelated – or removed the iron from – soft tissues taken from a T. rex and a Brachyolophosaurus, the chelated tissues reacted much more strongly to antibodies that detect the presence of protein, suggesting that the iron may be masking their presence in these preserved tissues. They then tested the preservation hypothesis by using blood vessels and cells taken from modern ostrich bone. They soaked some of these vessels in hemoglobin taken from , while placing other vessels in water. Two years later, the hemoglobin-treated soft vessels remained intact, while those soaked in water degraded in less than a week.

"We know that iron is always present in large quantities when we find well-preserved fossils, and we have found original vascular tissues within the bones of these animals, which would be a very -rich environment after they died," Schweitzer says. "We also know that iron hinders just about every technique we have to detect proteins. So iron looks like it may be both the mechanism for preservation and the reason why we've had problems finding and analyzing proteins that are preserved."

Explore further: Investigational drug effective in treating iron deficiency in kidney disease patients on dialysis

More information: "A role for iron and oxygen chemistry in preserving soft tissues, cells and molecules from deep time" Mary H. Schweitzer, et al. Proceedings of the Royal Society B, 2013.

Abstract
The persistence of original soft tissues in Mesozoic fossil bone 29 is not explained chemically by current chemical degradation models. We identified iron particles [goethite-αFeO(OH)] associated with soft tissues recovered from two Mesozoic dinosaurs, using TEM, EELS, μXRD, and Fe μXANES. Iron chelators increased fossil tissue immunoreactivity to multiple antibodies dramatically, suggesting a role for iron in both preserving and masking proteins in fossil tissues. Hemoglobin (HB) increased tissue stability ~50-fold, from ~ 3days to >six months at room temperature (25oC) in an ostrich blood vessel model developed to test postmortem "tissue fixation" by crosslinking or peroxidation. HB-induced solution hypoxia coupled with iron chelation enhances preservation as follows: HB + O2 > HB - O2 > - O2 >> + O2. The well-known O2/heme interactions in the chemistry of life, such as respiration and bioenergetics, are complemented by O2/heme interactions in the preservation of fossil soft tissues.

Related Stories

Ancient bug's last supper of blood still in fossil

Oct 14, 2013

In a steamy tropical forest 46 million years ago, a prehistoric mosquito bit a critter, drew blood and was blown into a lake in what is now the northwestern state of Montana. Belly full, she died and sank.

Drug approved for inherited blood disorder

Jan 24, 2013

(HealthDay)—Exjade (deferasirox) has been approved by the U.S. Food and Drug Administration to remove excess iron in the blood among people with a genetic blood disorder called non-transfusion-dependent thalassemia (NTDT).

Recommended for you

Crowd-sourcing Britain's Bronze Age

Apr 17, 2014

A new joint project by the British Museum and the UCL Institute of Archaeology is seeking online contributions from members of the public to enhance a major British Bronze Age archive and artefact collection.

Roman dig 'transforms understanding' of ancient port

Apr 17, 2014

(Phys.org) —Researchers from the universities of Cambridge and Southampton have discovered a new section of the boundary wall of the ancient Roman port of Ostia, proving the city was much larger than previously ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

On secondthoughtthinkagain
1 / 5 (2) Nov 26, 2013
Bring on Jurassic Park Again.
Sinister1811
not rated yet Nov 26, 2013
Bring on Jurassic Park Again.


And they were wasting their time with preserved mosquitoes. :P

More news stories

Study finds law dramatically curbing need for speed

Almost seven years have passed since Ontario's street-racing legislation hit the books and, according to one Western researcher, it has succeeded in putting the brakes on the number of convictions and, more importantly, injuries ...

Health care site flagged in Heartbleed review

People with accounts on the enrollment website for President Barack Obama's signature health care law are being told to change their passwords following an administration-wide review of the government's vulnerability to the ...

Airbnb rental site raises $450 mn

Online lodging listings website Airbnb inked a $450 million funding deal with investors led by TPG, a source close to the matter said Friday.