Heme compounds in dinosaur trabecular bone

Abstract

Six independent lines of evidence point to the existence of heme-containing compounds and͞or hemoglobin breakdown products in extracts of trabecular tissues of the large theropod dinosaur Tyrannosaurus rex. These include signatures from nuclear magnetic resonance and electron spin resonance that indicate the presence of a paramagnetic compound consistent with heme. In addition, UV͞visible spectroscopy and high performance liquid chromatography data are consistent with the Soret absorbance characteristic of this molecule. Resonance Raman profiles are also consistent with a modified heme structure. Finally, when dinosaurian tissues were extracted for protein fragments and were used to immunize rats, the resulting antisera reacted positively with purified avian and mammalian hemoglobins. The most parsimonious explanation of this evidence is the presence of blood-derived hemoglobin compounds preserved in the dinosaurian tissues.

A role for iron and oxygen chemistry in preserving soft tissues, cells and molecules from deep time

“…In life, blood cells rich in iron-containing HB flow through vessels, and have access to bone osteocytes through the lacuna-canalicular network [70,71]; after death, HB could cause localized, haeme-based radical cross-linking in dinosaur tissues. Moreover, HB-derived haeme, previously identified in dinosaur bone [72], has recently been identified in Miocene mosquitoes, supporting the durability of this prosthetic unit [73]. But are these reactions sufficient to result in long-term preservation?…”

“…Here, our data support a naturally occurring mechanism that results in stabilization of these presumably transient components over geological time. Because we observed iron particles in association with soft tissues in these fossils (figure 1), and earlier studies localized iron to the vessels of bone, not the bone matrix or surrounding sediments [72,85,86], we focused our attention on identifying a protein source for iron after death.…”

Hemoglobin-derived porphyrins preserved in a Middle Eocene blood-engorged mosquito

“…Blood vessels isolated from trabecular bone of the dinosaur Brachylophosaurus canadensis bound hemoglobinspecific antiserum in an immunosorbant assay, albeit with a signal only twice that of background levels (34). In immunoblot assays, antiserum raised against extracts of Tyrannosaurus rex trabecular bone reacted with purified hemoglobin but antiserum against hemoglobin did not react with extracts of B. canadensis bone (34,35). Both NMR and Raman spectroscopy have been applied to extracts of T. rex trabecular bone tissue, and data from both techniques were suggestive of the presence of heme and/or porphyrin (35).…”

“…In immunoblot assays, antiserum raised against extracts of Tyrannosaurus rex trabecular bone reacted with purified hemoglobin but antiserum against hemoglobin did not react with extracts of B. canadensis bone (34,35). Both NMR and Raman spectroscopy have been applied to extracts of T. rex trabecular bone tissue, and data from both techniques were suggestive of the presence of heme and/or porphyrin (35). The data reported herein provide incontrovertible documentation of the presence of heme-and arguably hemoglobin-derived porphyrins in a 46-million-year-old compression fossil and localize the porphyrins to a specific anatomical structure within that fossil.…”

A mosquito’s last supper reminds us not to underestimate the fossil record

“…Hemoglobin combines a protein with heme, the porphyrin ring structure that accommodates the iron involved in oxygen exchange. Heme as been detected in extracts of late Cretaceous dinosaur bone, using a variety of analytical techniques including NMR and Raman spectroscopy, as well as with immunological methods (17), and blood cells may also survive (18). The protein component of the hemoglobin in the mosquito's last meal was likely lost through decay, so the authors (1) used nondestructive methods (necessarily on a unique specimen) to test whether the heme survived.…”