Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session B42: Biomaterials 2: Structure, function, designInvited
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Sponsoring Units: DBIO Chair: Pupa Gilbert, Univ of Wisconsin, Madison Room: LACC 502B |
Monday, March 5, 2018 11:15AM - 11:51AM |
B42.00001: Biogenic Scatterers, Mirrors, Multilayer Reflectors and Photonic Crystals. Futuristic Ancient Technologies Invited Speaker: Leeor Kronik Organisms are able to construct an array of optical “devices” including diffuse scatterers, broadband reflectors, tunable photonic crystals and mirrors by varying the size, morphology and arrangement of organic crystals. These “devices” perform a variety of optical functions, such as generating the white color of certain spiders, the metallic silvery reflectance of fish scales, the brilliant iridescent colors of some copepods, and mirrors used for vision in animal eyes (1). Scallops have tens of eyes, each containing a concave multi-layered mirror tiled with a mosaic of square guanine crystals. The mirror forms images on a double-layered retina (2, 3). Shrimp, crayfish and lobsters possess compound eyes that also use reflective optics, and contain two sets of mirrors, composed of a previously unknown biogenic crystal – isoxanthopterine. The two mirrors have very different ultrastructures and functions that we can rationalize in terms of the optical performance of the eye. In all these examples, the hierarchical organization is controlled from the component crystals at the nanoscale to the complex 3D morphology at the millimeter level. |
Monday, March 5, 2018 11:51AM - 12:27PM |
B42.00002: Exceptional Preservation of Organic Matrix and Shell Ultrastructure in a Cretaceous Pinna Fossil Invited Speaker: Corinne Myers PhotoEmission Electron spectroMicroscopy (PEEM) was used to observe exceptional preservation in organic matrix components and shell ultrastructure in 66 Ma bivalve shell. PEEM is a novel method to detect, in situ, preservation quality, and provides a noninvasive, nondestructive, and spatially explicit map of prismatic and nacre tablet ultrastructure, mineralogy, crystal orientations, and organic compounds. This technique was used to compare Cretaceous and modern bivalves in the genus Pinna; results demonstrate that 66 Ma shells: (1) preserve original aragonite and calcite crystals in nacre and prismatic layers, respectively, (2) maintain nearly identical nacre tablet and prism ultrastructure and crystal orientations, and (3) preserve components of interprismatic proteins Remarkably, interprismatic proteins are preserved with intact peptide bonds and show an abundance of glycine, an important amino acid for protein folding and mechanical flexibility. Preservation of glycine chains in 66 Ma shells supports the exceptional quality of protein preservation documented here. Notably, this quality of preservation may not be uncommon among fossil shells with nacre, reflecting the entrapment and subsequent preservation of the molecular matrix by shell minerals. Thus, PEEM analysis provides new insight into the taphonomic processes influencing shell and molecular fossils, including the effects of molluscan diagenesis, physiology, biomineralization, and evolution. |
Monday, March 5, 2018 12:27PM - 1:03PM |
B42.00003: Investigation of the mineral and collagen arrangement in bone Invited Speaker: Frances Su The mineral arrangement in bone currently has three models: (1) the staggered crystal (most widely accepted) where the minerals are thought to be mainly in the gap regions between the collagen fibrils; (2) the wrapped crystal model where the minerals are extrafibrillar in the form of curved ribbons that wrap around collagen fibrils and (3) the interpenetrating composite model, where both mineral and collagen form their own networks that are intertwined with each other. Methods to investigate these models can be through complete demineralization or deproteinization experiments to examine each component separately. Six-month old porcine femur bones were either demineralized (HCl, CH2O2, EDTA, ETDA) or deproteinized (NaOCl, H2O2, NaOH, KOH). The resulting structures were characterized by x-ray diffraction, thermogravimetric analysis, scanning electron microscopy, Raman and Fourier transform infrared spectroscopy and compared to untreated bone. For demineralization, the CH2O2 treatment removed the most mineral meanwhile preserving the collagen structure. For deproteinization, NaOCl removed the most protein without altering the mineral structure. Although there is a minor amount of lipid in bone, a defatting process did not alter the findings. Both demineralization and deproteinization resulted in porous materials that remained structurally intact. The findings of these studies support the hypothesis that bone is an interpenetrating composite with continuous mineral and protein phases. These and more specific results will be discussed in the presentation. |
Monday, March 5, 2018 1:03PM - 1:39PM |
B42.00004: Correlative imaging techniques reveal organic-inorganic compositions of pathological mineral deposits Invited Speaker: Lara Estroff Pathological calcification is a wide-spread phenomenon in the human body, in which calcium minerals form in soft tissues and are found in both normal and damaged tissues. One example are microcalcifications (MCs) found in both benign and malignant breast tissue. Breast cancer is screened using mammography based on MC presence and appearance. Little is known, however, about their materials properties and associated organic matrix, or their correlation to breast cancer prognosis. One of the biggest questions regarding MC formation is whether they form by cell-mediated processes or are the result of cell-independent crystallization that is related to necrosis. We have used a combination of histopathology, Raman microscopy, and electron microscopy to image MCs within snap-frozen human breast tissue and have generated micron-scale resolution correlative maps of crystalline phase, trace metals, particle morphology, and organic matrix chemical signatures within high grade ductal carcinoma in situ (DCIS) and invasive cancer. This multimodal methodology lays the groundwork for establishing MC heterogeneity in the context of breast cancer biology, and has the potential to be applied to other pathological minerals, as well as in vitro models of mineralization. |
Monday, March 5, 2018 1:39PM - 2:15PM |
B42.00005: The solubility and structure(s) of amorphous calcium carbonate(s) (ACC) under controlled conditions Invited Speaker: Sebastian Mergelsberg Recent advances show multistep pathways to mineralization are widespread in biological and geological settings (De Yoreo et al., 2015, Science). The findings highlight the importance of amorphous intermediates in determining the composition of final crystalline products and indicate chemical signatures could record the properties of the initial amorphous phase. Thus, it is critical to understand the structure and physical properties of ACC and establish the mechanistic basis for the formation of carbonate minerals. |
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