title: Biogenic nanospheres of amorphous carbonated Ca-Mg phosphate within the periostracum of the green mussel Perna viridis.
abstract: Recently there is increasing evidence that the shell biomineralization proceeds via an amorphous precursor route. Therefore, the search for and investigation of amorphous biominerals in bivalve shells are of great importance and interest. Here, using a scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffractometer (XRD), and Fourier transform infrared spectrometer (FTIR), we investigate the microstructure and mineralogy of the periostracum in Perna viridis. We find that: (1) the periostracum has three layers, of which the inner and outer layer are of proteins, while the middle layer is mineralized with nanospheres of amorphous biominerals; (2) the nanospheres are of amorphous carbonated Ca-Mg phosphate (ACCP), where the CO3(2)(-)/PO4(3)(-) weight ratio is estimated to be ∼0.3, and the Ca/P and Ca/Mg atomic ratio is ∼1.4 and 1.6, respectively; (3) the nanospheres, with a diameter of 43-106nm, are found to assemble into spherules with a diameter of 160-500nm, which are further organized into parallel microlayers separated by the proteins; and (4) the nanospheres are assumed to function as the pH stabilizer to facilitate the shell's initial mineralization. Finally, we expect that these findings will advance our understanding of the shell's biomineralization process.
authors.affiliation: College of Materials Science and Engineering, Guangxi University, Nanning, Guangxi 530004, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Xu
authors.affiliation: College of Materials Science and Engineering, Guangxi University, Nanning, Guangxi 530004, China. Electronic address: zhanggs@gxu.edu.cn.
authors.forename: Gangsheng
authors.initials: G
authors.lastname: Zhang
mesh_terms: D060105:Animal Shells / Q000378:metabolism*; D000818:Animals; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D054118:Nanospheres / Q000378:metabolism*; D049883:Perna / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism*; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D010710:Phosphates
keywords: Amorphous carbonated Ca–Mg phosphate; Biomineralization; Green mussel; Nanosphere; Periostracum