Wallwork M L, Kirkham J, Chen H, Chang S-X, Robinson C, Smith D A, Clarkson B H
Leeds Dental Institute, University of Leeds, Leeds, UK.
Calcif Tissue Int. 2002 Sep;71(3):249-55. doi: 10.1007/s00223-001-1011-4. Epub 2002 Aug 6.
Noncollagenous matrix proteins (NCPs) of dental hard tissues (dentin, cementum) are involved, both temporally and spatially, in the mineralization of their collagen matrices. Two of the NCPs thought to initiate mineral nucleation and control crystal growth in dentin, are dentin phosphoproteins (DPP) and dentin sialoprotein (DSP). Control of crystal growth would depend on the binding capacity of these two molecules, which may be related to the charge domains on the crystals and/or the phosphorylation of the protein. Phosphophoryn (a highly phosphorylated DPP) and DSP were isolated, purified, and characterized from the immature root apicies of human teeth. Dephosphorylation of phosphophoryn was carried out using bovine intestinal alkaline phosphatase. Enamel crystals were prepared from the maturation stage of developing rat incisor enamel. Protein-coated crystals were prepared for viewing in an atomic force microscope fluid cell using tapping mode. Desorption of the proteins was achieved using a phosphate buffer and surface roughness measurements were obtained from all specimens. Time-lapsed images of the crystals showed "nanospheres" of protein distributed along the crystals but only the phosphophoryn-coated crystals showed a distinctive banding pattern, which was still visible after the phosphate desorption experiments. The surface roughness measurements were statistically greater (P <0.01) when compared to the control for only the phosphophoryn-coated specimens. It is hypothesized that the phosphophoryn binding may be associated with charge arrays on the crystal surface and its phosphorylation. Also, based on its affinity for the crystalsurfaces, phosphophoryn seems the most likely candidate for controlling dentin crystal growth and morphology.
牙齿硬组织（牙本质、牙骨质）的非胶原蛋白基质蛋白（NCPs）在时间和空间上都参与其胶原蛋白基质的矿化过程。牙本质磷蛋白（DPP）和牙本质涎蛋白（DSP）是两种被认为可启动牙本质矿核形成并控制晶体生长的NCPs。晶体生长的控制取决于这两种分子的结合能力，这可能与晶体上的电荷域和/或蛋白质的磷酸化有关。从人牙未成熟的根尖分离、纯化并鉴定了磷磷蛋白（一种高度磷酸化的DPP）和DSP。使用牛小肠碱性磷酸酶对磷磷蛋白进行去磷酸化处理。从发育中的大鼠切牙釉质的成熟阶段制备釉质晶体。制备蛋白质包被的晶体，以便在原子力显微镜流体池中采用轻敲模式进行观察。使用磷酸盐缓冲液实现蛋白质的解吸，并从所有标本中获得表面粗糙度测量值。晶体的延时图像显示蛋白质“纳米球”沿晶体分布，但只有磷磷蛋白包被的晶体呈现出独特的条纹图案，在磷酸盐解吸实验后该图案仍然可见。与对照组相比，仅磷磷蛋白包被的标本的表面粗糙度测量值在统计学上更高（P<0.01）。据推测，磷磷蛋白的结合可能与晶体表面的电荷阵列及其磷酸化有关。此外，基于其对晶体表面的亲和力，磷磷蛋白似乎是控制牙本质晶体生长和形态的最有可能的候选者。
