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

The lack of information on structural basis where proteins are involved, as well as the biomineralization processes of different systems such as bones, diatom frustules, and eggshells, have intrigued scientists from different fields for decades. This scientific curiosity has led to the use of methodologies that help understand the mechanism involved in the formation of these complex structures. Therefore, this work focuses on the use of eggshell membranes from different species of ratites (emu and ostrich) and reptiles (two species of crocodiles) as a model to differentiate biocalcification and biosilicification by introducing calcium phosphate or silica inside the membrane fiber mantles. We performed this to obtain information about the process of eggshell formation as well as the changes that occur in the membrane during crystal formation. In order to identify and understand the early processes leading to the formation of the microstructures present in the eggshell, we decided to carry out the synthesis of silica-carbonate of calcium, barium, and strontium called biomorph in the presence of intramineral proteins. This was carried out to evaluate the influence of these proteins on the formation of specific structures. We found that the proteins on untreated membranes, present a structural growth similar to those observed in the inner part of the eggshell, while in treated membranes, the structures formed present a high similarity with those observed in the outer and intermediate part of the eggshell. Finally, a topographic and molecular analysis of the biomorphs and membranes was performed by scanning electron microscopy (SEM), Raman and Fourier-transform Infrared (FTIR) spectroscopies.

Fractal Analysis of the Distribution and Morphology of Pores in Dinosaur Eggshells Collected in Mexico: Implications to Understand the Biomineralization of Calcium Carbonate.

In this work, we present an investigation of the surface area and roughness of different dinosaur eggshells of 70 million years old using fractal dimension analysis obtained from atomic force microscopy (AFM) and scanning electron microscopy (SEM) information. We also conduct qualitative analyses on the external and inner surfaces of eggshells, which are mainly composed of calcium carbonate. The morphological characteristics of both surfaces can be revealed by both SEM and AFM techniques. It is observed that the inner surface of the eggshell has greater roughness that increases the surface area due to the vaster number of pores compared to the external face, making, therefore, the fractal dimension also greater. The aim of this contribution is to identify the morphology of the pores, as well as the external and inner surfaces of the eggshells, since the morphology is very similar on both surfaces and will otherwise be difficult to determine with the naked eye by SEM and AFM. In addition, the sole AFM analysis is very complicated for these types of samples due to the intrinsic roughness. However, it needs additional methods or strategies to complete this purpose. This contribution used the fractal dimension to show the same behavior obtained in both SEM and AFM techniques, indicating the fractal nature of the structures.

Searching for a Clue to Characterize a Crystalline Dinosaur's Eggshell of Baja California, Mexico.

This work presents a detailed structural and morphological analysis of different dinosaur eggshells such as Spheroolithus (sample 1, 2), lambeosaurinae, Prismatoolithus, and one unidentified ootaxon performed by high-resolution scanning electron microscopy (HRSEM). These ancient eggshells of Late Cretaceous dinosaurs were collected in the coastal area of El Rosario, Baja California in Mexico. Additionally, a thorough study was performed on the elements present in the samples by different techniques such as energy-dispersive spectroscopy (EDS), X-ray fluorescence (XRF), and X-ray photoelectron spectroscopy (XPS). The XPS technique was performed to make an accurate identification of the compounds of two different types of eggshells (Spheroolithus sample 1 and Prismatoolithus). This contribution compares the surface of five different dinosaur eggshells of 74 Ma and their inner section to determine the morphology, distribution of the chemical elements present, as well as their relationship. The observed morphology of the ornithopod eggshells of the herbivorous species shows that the mammillary cones are in the form of columns with microaggregates and irregular pores. In contrast, in the theropod eggshells, the mammillary cones are observed in different forms with wider pores. Finally, the chemical components present in the structures of each of the samples were estimated using the information obtained from SEM-EDS, evidencing the presence of calcite, quartz, and albite in each of the samples. The composition reveals that eggshells contain Si, P, S, K, Ca, Mn, Fe, and Sr and trace elements such as Cr, Cu, and Zn. The presence of heavy metals may be an indication that the eggshells presented diagenetic alterations.