Abstract
Biominerals are highly ordered crystals mediated by organic matters especially proteins in organisms. However, how specific proteins are distributed inside biominerals are not well understood. In the present study, we use fluorescein isothiocyanate (FITC) to label extracted proteins from the shells of bivalve Pinctada fucata. By confocal laser scanning microscopy (CLSM), we observe a heterogeneous distribution of dye-labelled proteins inside synthetic calcite at the microscale. Proteins from the prismatic calcite layers accumulate at the edge of crystals while proteins from the nacreous aragonite layers accumulate at the center of crystals. Raman and X-ray powder diffraction show that both the proteins cannot alter the crystal phase. Scanning electron microscope demonstrates both proteins are able to affect the crystal morphology. This study may provide a direct approach for the visualization of protein distributions in crystals by small-molecule dye-labelled proteins as the additives in the crystallization process and improve our understanding of intracrystalline proteins distribution in biogenic calcites.
Highlights
Weber et al recently use recombinant green fluorescent protein (GFP)-fusion proteins to study the effects of perlucin- a lectin protein from the nacre of mollusk Haliotis lavigata- on the crystallization of CaCO3 and visualize them by confocal laser scanning microscopy (CLSM)[17,18]
The results show that proteins from different parts of shells have different distribution patterns inside the synthetic calcite, which may reflect their different roles in CaCO3 crystal growth
By using Fluorescein isothiocyanate (FITC)-labeled proteins extracted from the shell of Pinctada fucata as the additives, a heterogeneous distribution of biomineral-associated matrix proteins inside synthetic calcite at the microscale was observed for the first time according to the fluorescence intensity
Summary
Weber et al recently use recombinant green fluorescent protein (GFP)-fusion proteins to study the effects of perlucin- a lectin protein from the nacre of mollusk Haliotis lavigata- on the crystallization of CaCO3 and visualize them by confocal laser scanning microscopy (CLSM)[17,18]. Last but not the least, some researchers use the immunolocalization approach, in which antibodies against biomineralization proteins are used to localize the specific proteins in the shells of Pinna nobilis[21] and to observe skeletal matrix proteins in the mineral of the coral Stylophora pistillata[22] This method can indirectly observe the spatial relationship between the organic and mineral phases, but it cannot reflect how proteins are distributed within the mineral. The shell of the pearl oyster, P.fucata, which is widely used to produce saltwater pearls in China and East Asia, consists of two different forms of calcium carbonate, i.e. calcite in the outer prismatic layer and aragonite in the inner nacreous layer[25] They have been extensively used as a biomineralization model to explore relationship between macromolecules and calcium carbonate crystallization[26,27]. The results raise a possibility that different proteins controlling crystal growth in natural biominerals have different distributions and locations
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
