Resonance Raman confirms partial hemoglobin preservation in dinosaur remains

Still-soft, hollow, and flexible structures  that are morphologically consistent with blood vessels were recovered from demineralized dinosaur bone and studied with resonance Raman techniques to test the hypothesis that these vessel-like structures are original to the dinosaur, and that they maintain endogenous molecular characteristics. We probed these ancient samples using resonance Raman at two different wavelengths, and the existence of a stronger resonance Raman signal level in the green compared to blue excitation is consistent with a hemoglobin, not just heme, absorption resonance. These data imply that the heme moieties preserved in dinosaur soft tissue are still attached to remnant proteins, or fragments thereof. Further, analysis of the Raman spectra of these hemoglobin remnants show damage to the outer regions of the heme ring, indicative of diagenetic change and thus consistent with an ancient endogenous source. Separately, the formation of goethite crystallites still attached to the hemoglobin remnant suggest a possible mechanism for preservation. The latter result follows from the fact that Raman signal resonance occurs only for vibrations on the same molecule as the absorption causing the resonance. Modern and artificially aged analogs show the beginnings of similar processes.