Posted on 04/12/2007 12:43:57 PM PDT by AdmSmith
68-million-year-old T. rex proteins are oldest ever sequenced
Scientists have confirmed the existence of protein in soft tissue recovered from the fossil bones of a 68 million-year-old Tyrannosaurus rex (T. rex) and a half-million-year-old mastodon.
Their results may change the way people think about fossil preservation and present a new method for studying diseases in which identification of proteins is important, such as cancer.
When an animal dies, protein immediately begins to degrade and, in the case of fossils, is slowly replaced by mineral. This substitution process was thought to be complete by 1 million years. Researchers at North Carolina State University (NCSU) and Harvard Medical School now know otherwise.
The researchers' findings appear as companion papers in this week's issue of the journal Science.
"Not only was protein detectably present in these fossils, the preserved material was in good enough condition that it could be identified," said Paul Filmer, program director in the National Science Foundation (NSF) Division of Earth Sciences, which funded the research. "We now know much more about what conditions proteins can survive in. It turns out that some proteins can survive for very long time periods, far longer than anyone predicted."
Mary Schweitzer of NCSU and the North Carolina Museum of Natural Sciences discovered soft tissue in the leg bone of a T. rex and other fossils recovered from the Hell Creek sediment formation in Montana.
After her chemical and molecular analyses of the tissue indicated that original protein fragments might be preserved, she turned to colleagues John Asara and Lewis Cantley of Harvard Medical School, to see if they could confirm her suspicions by finding the amino acid used to make collagen, a fibrous protein found in bone.
Bone is a composite material, consisting of both protein and mineral. In modern bones, when minerals are removed, a collagen matrix--fibrous, resilient material that gives the bones structure and flexibility--is left behind. When Schweitzer demineralized the T. rex bone, she was surprised to find such a matrix, because current theories of fossilization held that no original organic material could survive that long.
"This information will help us learn more about evolutionary relationships, about how preservation happens, and about how molecules degrade over time, which could have important applications in medicine," Schweitzer said.
To see if the material had characteristics indicating the presence of collagen, which is plentiful, durable and has been recovered from other fossil materials, the scientists examined the resulting soft tissue with electron microscopy and atomic force microscopy. They then tested it against various antibodies that are known to react with collagen. Identifying collagen would indicate that it is original to T. rex--that the tissue contains remnants of the molecules produced by the dinosaur.
"This is the breakthrough that says it's possible to get sequences beyond 1 million years," said Cantley. "At 68 million years, it's still possible."
Asara and Cantley successfully sequenced portions of the dinosaur and mastodon proteins, identifying the amino acids and confirming that the material was collagen. When they compared the collagen sequences to a database that contains existing sequences from modern species, they found that the T. rex sequence had similarities to those of chickens, and that the mastodon was more closely related to mammals, including the African elephant.
The protein fragments in the T. rex fossil appear to most closely match amino acid sequences found in collagen of present-day chickens, lending support to the idea that birds and dinosaurs are evolutionarily related.
"Most people believe that birds evolved from dinosaurs, but that's based on the 'architecture' of the bones," Asara said. "This finding allows us the ability to say that they really are related because their sequences are related."
"Scientists had long assumed that the material in fossil bones would not be preserved after millions of years of burial," said Enriqueta Barrera, program director in NSF's Division of Earth Sciences. "This discovery has implications for the study of similarly well-preserved fossil material."
I’ve worked extensively with both Gas Chromatographs and Mass Spectrometers. Although, I am not saying the method you mention is unreliable to the point it negates the findings, they themselves post some interesting conclusions:
“The use of MALDI spectrometry alone is rarely sufficient to identify a protein. If the protein is not mixed, and gives rise to several peptides, and several of these give matches against the same protein in a good complete library for the species, it may be possible to obtain an identification. More often, MALDI spectrometry cannot prove what protein was present, but can provide a list of likely candidates. This is useful, as then the peptides that provide evidence for these candidate proteins can be taken forward for MS/MS spectrometry, which is more likely to provide convincing proof of protein identity.”
While I can't post the whole article, I can post a paragraph that discusses some of their findings and their reasons for thinking that this experiment shows the presence of genuine fragments of T. rex collagen:
A BLAST alignment and similarity search (23) of the five T. rex peptides from collagen 1t1 as a group against the all-taxa protein database showed 58% sequence identity to chicken, followed by frog (51% identity) and newt (51% identity). The small group of peptide sequence data reported here support phylogenetic hypotheses suggesting that T. rex is most closely related to birds among living organisms whose collagen sequence is present in protein databases (24–26). The collagen sequences from other closely related extant taxa such as alligator (Alligator sinensis) and crocodile (Crocodylus acutus) are not present in current protein databases. If all sequences were consistent with a single extant organism, it might indicate that the samples or our experiments were contaminated. However, we identified regions of sequence that align uniquely with multiple related vertebrate taxa in protein databases. The highly conserved nature of collagen proteins results in very limited regions that do not overlap, and the sequence alignments vary by only one or two amino acids, even in distantly related organisms. Because these peptides are all derived from the same bone matrix, one would have to make the argument for multiple contamination events from organisms, such as newt, that are not native to Hell Creek environments and have never been inside the buildings that have housed these bone samples. For further validation of the sequence data, Fig. 3 shows one of the experimental T. rex sequences, GVQGPP(OH)GPQGPR (27), that matched to chicken collagen 1t1 and the synthetic version of the peptide. The experimental spectrum shows lower signal intensity and more chemical noise than the synthetic peptide, which is not surprising because the spectra were derived from 68-million-year-old endogenous proteins. The signal intensities of the mass spectra indicate that only low or subfemtomole levels of peptides were produced from tryptic digestions of approximately 30 mg of bone protein extract. Peptide sequences unique to T. rex were not found, most likely because few peptides were available for sequencing as compared to the ostrich and mastodon samples. In support of these results and data shown here and by Schweitzer et al. (11), in situ localization with avian antibodies to collagen type 1 shows the presence of collagen, which disappears after treatment with collagenase (11).
Asara, J. M.; Schweitzer, M. H.; Freimark, L. M.; Phillips, M.; Cantley, L. C. "Protein sequences from mastadon and Tyrannosaurus rex revealed by mass spectroscopy." Science 2007, 316, 280.
This is why one should always check the original articles, and not rely on the popular sources.
The popular articles, unfortunately, are generally written by "journalists" rather than scientists.
[Translation -- they haven't a clue and figure none of their readers do either. Besides, science is hard!]
Dinosaur protein sequenced - Lucky find shows up record-breaking fossil.
news@nature.com | 12 April 2007 | Heidi Ledford
Posted on 04/13/2007 6:14:00 PM EDT by neverdem
http://www.freerepublic.com/focus/f-news/1817005/posts
BBC: Protein links T. rex to chickens ~ ummm tasty....
BBC | Thursday, 12 April 2007, 19:27 GMT 20:27 UK | Paul Rincon Science reporter, BBC News
Posted on 04/12/2007 4:57:11 PM EDT by Ernest_at_the_Beach
http://www.freerepublic.com/focus/f-news/1816370/posts
Scientists Retrieve Proteins From Dinosaur Bone
New York times | April 12, 2007 | JOHN NOBLE WILFORD
Posted on 04/12/2007 5:05:00 PM EDT by gcruse
http://www.freerepublic.com/focus/f-news/1816375/posts
Dinosaur research backs link to birds
AP on Yahoo | 4/14/07 | Randolph E. Schmid - ap
Posted on 04/15/2007 1:18:48 AM EDT by NormsRevenge
http://www.freerepublic.com/focus/f-news/1817592/posts
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:’)
Well, I tried!
Are EVERYONES posts now “being reviewed” before posting? I’ve looked for a thread on it, but can’t find one.
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