Molecular Analysis of the Mineral Phase and Examination of Possible Intramineral Proteins of Dinosaur Eggshells Collected in El Rosario, Baja California, Mexico

Abstract

We performed a molecular analysis of dinosaur's eggshells collected in El Rosario, Baja California, using techniques such as Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRPD), and photoluminescence spectroscopy (PS). These techniques allowed us to identify calcite as the main mineral. The crystalline planes corresponding to this mineral were obtained with a hexagonal unit cell by Rietveld refinement. In addition, six crystallographic planes corresponding to quartz were identified by XRPD, with a rather large crystallite size compared to those obtained from calcite and albite. For this latter mineral, found in a low content, we were able to identify only three crystalline planes and three wavelengths of photoluminescence and micro-Raman signals at a very low intensity. In addition, the analysis by FT-IR allowed us to identify bands corresponding to nine amino acids and the components of the secondary structure that might very well be some ancestral proteins that had been conserved for so long, thanks to the mineralized structure. This type of structural characterization together with the optical one is a very relevant contribution to the field of paleontological research, mainly because these types of samples are unique in their type due to the biological relevance in Mexico that will allow us to understand the species that became extinct millions of years ago.

Influence of Intramineral Proteins on the Growth of Carbonate Crystals Using as a Scaffold Membranes of Ratite Birds and Crocodiles Eggshells

“…As in the case of the untreated membranes, the biocalcified membranes were analyzed by FTIR and the signals corresponding to the hydroxyapatite calcium phosphate present in the membrane fibers were observed (Figure 13 and Tables S8-S11). One of these signals corresponds to the tension (ν) of the hydroxyl (-OH), which vibrates at ~3300 cm −1 , it is typical of biogenic hydroxyapatite found in membrane [50], where the collagen presence lowers the (-OH) infrared peak of mineral hydroxyapatite of 3570 cm −1 . The other signals correspond to the vibration modes [ν1+ν3] and [ν2+ν4] of the phosphate group ((PO 4 ) 3− ), which were observed at ~950-1100 cm −1 and ~520-650 cm −1 , respectively [53][54][55].…”

“…Next, we see the bending vibration signal of the methyl group (-CH 2 ) at ~1480-1430 cm −1 and that of the ν 3 mode corresponding to the carbonate ((CO 3 ) 2− ) between ~1420-1350 cm −1 . Subsequently, we see the amide group III which gives information about the vibrations of the hydrogen bonds of the amino acids and is found at wavenumbers from ~1450-1200 cm −1 [50,51]. Finally, the ν 2 mode of carbonate ((CO 3 ) 2− ) is found at a wavenumber about ~870 cm −1 , which is not observed in the untreated membranes, giving us a sign that the calcium carbonate mineral of the mineral phase of the eggshell has indeed been completely dissolved during the cleaning with acetic acid and 3-mercaptopropionic acid (see Section 2).…”

Apatite in Hamipterus tianshanensis eggshell: advances in understanding the structure of pterosaur eggs by Raman spectroscopy

“…Meanwhile, Raman spectroscopy, as a non-destructive test, has drawn much attention in fossil egg researchers. For example, Raman spectroscopy can be used to identify the chemical composition of fossil eggshell [25], such as the hydroxyapatite (HAP) preserved in the cuticle layer [26], phosphate in the membrane [27], and color-producing pigments [28][29][30], S-to N-heterocycles [31], and amorphous carbon [32]. Moreover, Raman spectroscopy with the deconvolution technique can be used to detect the maximum paleotemperature recorded in eggshells [33].…”