in nacre. Moreover, the inorganic aragonite phase also plays an active role in
organizing nacre microstructure. Based on these studies, several models to illustrate
the formation mechanism related to lamellar nacre in bivalves, and columnar nacre
in gastropods are introduced.
12.1 Introduction
The nacreous layer (mother-of-pearl) of the molluskan shell is a microlamellar
composite of highly oriented aragonitic crystals and proteins, exhibiting exceptional regularity, high mechanical strength (Meyers et al. 2008), and great thermal
stability (Balmain et al. 1999). Its structure and properties gives it potential for the
treatment of bone deficiencies (Westbroek and Marin 1998; Balmain et al. 1999;
Lamghari et al. 1999) and in materials synthesis. Biomineralization, by definition a
multidisciplinary field, especially the biomineralization of the nacreous layer, has
attracted researchers from various scientific fields such as, biology, biotechnology,
physics, chemistry, geology, and material science etc. The study of nacre biomineralization not only offers valuable insights into the scope and nature of materials,
but also may provide new ideas for improved design of synthetic materials (Mann
1993; Aksay et al. 1996; Weiner and Addadi 1997).
Recently, many new techniques have been used in the study of the nacreous
layer, such as FESEM (field-emission scanning electron microscopy), FETEM
(field-emission transmission electron microscopy) (Oaki and Imai 2005), Confocal
and IR (Dauphin et al. 2008), environmental and cryo-scanning electron microscopy
(Nudelman et al. 2008), and AFM (atomic force microscopy) (Bezares et al. 2008).
With the development and use of new techniques and biotechnology, more and
more advances have been made in the illustration of the structure of the nacreous
layer at a nanoscale, and in the characterization of increasing numbers of matrix
proteins (Marin et al. 2008). Information on the following four aspects facilitates
speculation on the primary and secondary structure of matrix proteins and their
functions: (1) the gene sequences encoding the matrix proteins, (2) the deduced
amino acid sequences, (3) gene expression character in the mantle, and (4) their
distribution in the interlamellar sheets of the nacreous layer. Several researchers
have reviewed investigations on matrix proteins (Marin and Luquet 2004; Samata
2004; Cusack and Freer 2008; Marin et al. 2008) and biomineralization of shell
(Cusack and Freer 2008).
This paper briefly introduces the recent research advances at the molecular level
on the nacre layers of shells (mainly from bivalves and gastropods), which range
from analyzing the micro- and nano-structure and components of shell nacreous
layers, to illustrating the characteristics and functions of matrix proteins from nacre.
Matrix proteins not only participate in construction of the organic nacre framework,
but also control the nucleation and growth of aragonitic crystals, as well as the
polymorph specificity of calcium carbonate in nacre. Moreover, the inorganic
aragonite phase also plays an active role in organizing nacre microstructure.
332
L.-p. Xie et al.
organizing nacre microstructure. Based on these studies, several models to illustrate
the formation mechanism related to lamellar nacre in bivalves, and columnar nacre
in gastropods are introduced.
12.1 Introduction
The nacreous layer (mother-of-pearl) of the molluskan shell is a microlamellar
composite of highly oriented aragonitic crystals and proteins, exhibiting exceptional regularity, high mechanical strength (Meyers et al. 2008), and great thermal
stability (Balmain et al. 1999). Its structure and properties gives it potential for the
treatment of bone deficiencies (Westbroek and Marin 1998; Balmain et al. 1999;
Lamghari et al. 1999) and in materials synthesis. Biomineralization, by definition a
multidisciplinary field, especially the biomineralization of the nacreous layer, has
attracted researchers from various scientific fields such as, biology, biotechnology,
physics, chemistry, geology, and material science etc. The study of nacre biomineralization not only offers valuable insights into the scope and nature of materials,
but also may provide new ideas for improved design of synthetic materials (Mann
1993; Aksay et al. 1996; Weiner and Addadi 1997).
Recently, many new techniques have been used in the study of the nacreous
layer, such as FESEM (field-emission scanning electron microscopy), FETEM
(field-emission transmission electron microscopy) (Oaki and Imai 2005), Confocal
and IR (Dauphin et al. 2008), environmental and cryo-scanning electron microscopy
(Nudelman et al. 2008), and AFM (atomic force microscopy) (Bezares et al. 2008).
With the development and use of new techniques and biotechnology, more and
more advances have been made in the illustration of the structure of the nacreous
layer at a nanoscale, and in the characterization of increasing numbers of matrix
proteins (Marin et al. 2008). Information on the following four aspects facilitates
speculation on the primary and secondary structure of matrix proteins and their
functions: (1) the gene sequences encoding the matrix proteins, (2) the deduced
amino acid sequences, (3) gene expression character in the mantle, and (4) their
distribution in the interlamellar sheets of the nacreous layer. Several researchers
have reviewed investigations on matrix proteins (Marin and Luquet 2004; Samata
2004; Cusack and Freer 2008; Marin et al. 2008) and biomineralization of shell
(Cusack and Freer 2008).
This paper briefly introduces the recent research advances at the molecular level
on the nacre layers of shells (mainly from bivalves and gastropods), which range
from analyzing the micro- and nano-structure and components of shell nacreous
layers, to illustrating the characteristics and functions of matrix proteins from nacre.
Matrix proteins not only participate in construction of the organic nacre framework,
but also control the nucleation and growth of aragonitic crystals, as well as the
polymorph specificity of calcium carbonate in nacre. Moreover, the inorganic
aragonite phase also plays an active role in organizing nacre microstructure.
332
L.-p. Xie et al.