Dinosaur DNA and Proteins

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Dinosaur DNA and proteins found, according to Science 2.0 20 October 2012, North Carolina State University News 23 October 2012 and Bone 16 October 2012 doi: 10.1016/j.bone.2012.10.010. A group of scientists led by Mary Schweitzer of North Carolina State University have confirmed previous research that proteins can be found in dinosaur bones. Schweitzer first identified preserved soft tissue in dinosaur bone in 2005. In 2007 she and her colleagues used chemical tests to confirm that fibrous material collected from a Tyrannosaurus rex dated as 67 million years old, and a Brachylophosaurus dated as 80 million years old was collagen, the tough fibrous protein found in bones, tendons and ligaments. The research team have now examined star shaped structures that look like osteocytes, bone cells, within the dinosaur bones.

Critics of Schweitzer’s previous research had suggested that protein material found within the bones was from microbes that had contaminated the specimens. To answer this, the team used antibodies that bind to proteins found in vertebrate bone cells, but not protein found in microbes. One of the proteins they tested for is named PHEX and is found in osteocytes of living birds. Schweitzer explained: “The PHEX finding is important because it helps to rule out sample contamination. Some of the antibodies that we used will react to proteins found in other vertebrate cells, but none of the antibodies react to microbes, which supports our theory that these structures are surviving osteocytes. Additionally, the antibody to PHEX will only recognize and bind to one specific site only found in mature bone cells from birds. These antibodies don’t react to other proteins or cells. Because so many other lines of evidence support the dinosaur/bird relationship, finding these proteins helps make the case that these structures are dinosaurian in origin”. The team also tested for the presence of DNA by using an antibody that only binds to the “backbone” of DNA. They also got positive results using two fluorescent chemical dyes that attach to DNA. To confirm the DNA was not from contaminating microbes they also tested for histone proteins. These are proteins involved in the packaging of DNA but are not found in bacteria.

There is a great deal of scepticism amongst the mainstream scientific community that proteins, DNA and soft tissue could be preserved for 67 million years. Schweitzer’s team suggest the proteins and DNA were preserved by the fact they are already embedded in a mineral matrix within the bone, and maybe iron from red blood cells formed cross-linking bridges between the proteins and other cellular molecules and made them resistant to being degraded. Schweitzer summarised the results: “The data thus far seem to support the theory that these structures can be preserved over time. Hopefully these findings will give us greater insight into the processes of evolutionary change.”

North Carolina University, Science 2.0

Editorial Comment: Six days before this study was released online in Bone, Morten Allentoft at the University of Copenhagen and Michael Bunce at Murdoch University in Perth, Australia published a study in Proceeding of the Royal Society B doi: 10.1098/rspb.2012.1745 claiming DNA has a half-life of 521 years. It most likely means that after 521 years, in 50% of the DNA in a normal environment, (not frozen in a laboratory) the bond breakage is so complete that it is no longer recognizable as DNA anymore. So long before Schweitzer’s desired “67 million years” there would be none left. Recovering dinosaur DNA was the basis of the story in the film Jurassic Park, but according to Allentoft: “What we show here with the decay rate of DNA is that this is never going to be possible”. (See DNA dating study kills off 'Jurassic Park', ABC News in Science, 10 October 2012 here.)

When we combine this with the fact that Ronald Raines of University of Wisconsin–Madison reminded the scientific community in 2009, that proteins are subject to decay since proteins are held together by peptide bonds and each “peptide bond has a half-life of 400 years”. (Adv Exp Med Biol. 2009; 611: xci–xcviii) Therefore, collagen and all the other proteins North Carolina scientists have found in dinosaur bones cannot last millions, but only thousands of years.

There is an obvious solution to this problem: T. rex and Brachylophosaurus bones are not 67 or 80 million years old, but at most 4-5 thousands of years old. What interesting times we live in for creationists. (Ref. age, dating, time)

Evidence News 7 November 2012

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