Crystal formation and growth in bivalve nacre

X‐ray diffraction study of the insoluble organic matrix of mollusk shells

“…We have not observed any Observed intensities (Zo) were estimated as very strong (vs), strong (s), moderately strong (ms), medium (m), moderately weak (mw) or weak (w) and are listed for orientation (2). Observed orientations are given for the X-ray beam in three orthogonal directions (1) perpendicular to and (2) and ( We have obtained only a few preliminary X-ray photographs from organic matrices of other mollusk shells, but these generally resemble the two described above and presumably imply similar structures.…”

“…The organic matrix is observed to form prior to mineralization [ 1,2], and it has been suggested that some of the matrix protein components may serve as a template for mineral deposition . The calcium carbonate of the shell can be dissolved in EDTA leaving an insoluble fraction which comprises the bulk of the organic matrix [5, 7,8] and consists of a heterogeneous mixture of proteins and carbohydrate [9-l 21.…”

Molecular Cloning and Characterization of Lustrin A, a Matrix Protein from Shell and Pearl Nacre of Haliotis rufescens

“…Although the organic components typically constitute only ϳ1% by weight of the biomineralized composite material (17), they are responsible for its organization and the resulting enhancement of fracture toughness (3-7, 18 -21). Proteins represent the majority of extracellular organic polymers controlling biomineralization of the shell (8 -10); they comprise at least four functional classes, including (i) a nucleating sheet that participates in control of nucleation of the first layer of oriented calcite in deposition of the abalone shell and flat pearl (13, 14, 22), (ii) a family of polyanionic proteins that can be extracted by demineralization of the shell (8 -10, 17, 23-25) and have been shown in vitro to control the polymorph and atomic lattice orientation by cooperative interaction with the growing crystals (22,26,27), (iii) proteins of an insoluble, highly cross-linked matrix, forming an organizing network of interconnected compartments and fenestrated sheets that control the morphology and higher order packing of the CaCO 3 crystals (8, 22, 28 -32), and (iv) functional enzymes, such as carbonic anhydrase (33), that apparently contribute to the control of biomineralization.Nacre consists of layers of interlocking thin tablets of aragonite (one of the polymorphs of CaCO 3 ) typically 400 nm thick and 5-10 m wide surrounded on all sides by thin sheets of organic matrix approximately 30 nm thick (7,29,30,34). The thickness of the mineral tablets apparently is determined by the matrix sheets (22), while their interdigitation is controlled, in part, by the stochastic location of nanopores in the stencillike sheets through which the crystals grow from one layer to the next (32,(35)(36)(37)(38).…”

“…Nacre consists of layers of interlocking thin tablets of aragonite (one of the polymorphs of CaCO 3 ) typically 400 nm thick and 5-10 m wide surrounded on all sides by thin sheets of organic matrix approximately 30 nm thick (7,29,30,34). The thickness of the mineral tablets apparently is determined by the matrix sheets (22), while their interdigitation is controlled, in part, by the stochastic location of nanopores in the stencillike sheets through which the crystals grow from one layer to the next (32,(35)(36)(37)(38).…”

A possible mechanism for the formation of annual growth lines in bivalve shells

“…Historically, it was thought that the interprismatic organic membrane of the prism was created by squeezing between the prisms during their formation [23,24]. However, Checa et al [25] proposed that calcite grows in organic cavities that are formed at an earlier stage.…”