http://rdu.iquimica.unam.mx/handle/20.500.12214/21 2026-04-19T13:28:04Z 2026-04-19T13:28:04Z Abel MORENO http://rdu.iquimica.unam.mx/handle/20.500.12214/1313 2021-08-21T19:27:28Z 2021-01-01T00:00:00Z

Title: Fractal analysis of the distribution and morphology of pores in dinosaur eggshells collected in Mexico: implications to understand the biomineralization of calcium carbonate Author: Abel MORENO Abstract: 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.

2021-01-01T00:00:00Z Abel MORENO http://rdu.iquimica.unam.mx/handle/20.500.12214/1302 2021-08-04T17:43:15Z 2021-01-01T00:00:00Z

Title: The influence of silicateins on the shape and crystalline habit of silica carbonate biomorphs of alkaline earth metals (Ca, Ba, Sr) Author: Abel MORENO Contributor: Juana Virginia Tapia Vieyra Abstract: This contribution presents the effect of two ortholog enzymes from marine sponges called silicateins on the formation of silica carbonate biomorphs of alkaline metals (Ca, Ba, Sr). In vivo, these enzymes participate in the polymerization of silica. Silicateins from Tethya aurantia and Suberitis domuncula were produced recombinantly and presented different degrees of activity, as evidenced by their ability to cleave silyl ether-like bonds in a model compound. Biomorphs are typically inorganic structures that show characteristic shapes resembling those of biological structures such as helices, leaves, flowers, disks or spheres. Irrespective of the concentration or the enzyme used, the presence of silicateins inhibited the formation of classic morphologies of biomorphs, albeit to different extents. Thus, not only the silica condensation activity of the enzyme but also its ability to bind silica compounds is implicated in the inhibition process. The largest effect was observed for the strontium and barium biomorphs, leading to the formation of spheres similar to those observed in diatoms and Radiolaria rather than the classical non-symmetrical forms. Characterization of the samples using Raman spectroscopy showed that silicatein did not affect the crystalline structure of the alkaline earth metal carbonate but did modify the crystalline habit.

2021-01-01T00:00:00Z Abel MORENO http://rdu.iquimica.unam.mx/handle/20.500.12214/1300 2021-06-07T18:36:42Z 2020-01-01T00:00:00Z

Title: Biocrystals in plants: a short review on biomineralization processes and the role of phototropins into the uptake of calcium Author: Abel MORENO Abstract: The biomineralization process is a mechanism inherent to all organisms of the Earth. Throughout the decades, diverse works have reported that the origin of life is tied to crystals, specifically to biominerals of silica that catalyzed RNA, and had some influence in the homochirality. Although the mechanism by which crystals surfaces (minerals) gave origin to life has not yet been proven, the truth is that, up to the present, biominerals are being synthetized by the organisms of different kingdoms in two basic ways: biologically induced and biologically controlled biomineralization. Paradoxically, this fact makes a fundamental difference between inorganic materials and those formed by living organisms, as the latter are associated with macromolecules that are bound to the mineral phase. Conserving growth and formation of these biogenic organic crystals inside cells is a fascinating subject that has been studied mainly in some of the kingdoms, like Monera (bacteria), Fungi (yeasts), and Animalia (Homo sapiens). Notwithstanding in the Plantae kingdom, the formation, conservation, and functions of crystals has not yet been completely elucidated and described, which is of particular relevance because life on Earth, as we know it, would not be possible without plants. The aim of the present work is to revise the different crystals of calcium oxalate synthetized inside the cells of plants, as well as to identify the mechanism of their formation and their possible functions in plants. The last part is related to the existence of certain proteins called phototropins, which not only work as the blue-light sensors, but they also play an important role on the accumulation of calcium in vacuoles. This new trend is shortly reviewed to explain the characteristics and their plausible role in the calcium uptake along with the biomineralization processes.

2020-01-01T00:00:00Z Abel MORENO http://rdu.iquimica.unam.mx/handle/20.500.12214/1299 2021-06-07T18:01:54Z 2020-01-01T00:00:00Z

Title: Searching for a clue to characterize a crystalline dinosaur’s eggshell of Baja California, Mexico Author: Abel MORENO Abstract: 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.

2020-01-01T00:00:00Z