人胚牙本质磷蛋白的提取

目的　提取人胚胎牙胚中牙本质磷蛋白并分析其特性。方法　从胎龄 2 5～ 33周的胚胎中获得牙胚 ,以 0 .2 5 mol/L EDTA脱矿直至无 Ca2 + 析出 ,用 4 m ol/L盐酸胍抽提后浓缩得到人胚牙本质磷蛋白。SDS- PAGE测定其相对分子质量 ,水解法测定氨基酸构成比。结果　在胚胎中获得的牙本质磷蛋白由 3个相对分子质量分别为14 0× 10 3、12 5× 10 3和 76× 10 3的组分组成 ,氨基酸中天门冬氨酸含量达 4 1.2 % ,丝氨酸为 2 8.5 %。结论　采用 0 .2 5 mol/L EDTA和 4 mol/L盐酸胍可以从人牙胚胎中提取出牙本质磷蛋白 ,其相对分子质量为 76× 10 3～ 14 0×10 3,其氨基酸组成与根尖孔未封闭离体牙中获得者相似 ,富含天门冬氨酸和丝氨酸。

Extraction and Characterization of Dentin Phosphophoryn from Human Embryo

OBJECTIVE: To extract the dentin phosphophoryn (DPP) from human embryo and analyze its characteristic. METHODS: Eight dental germs collected from the human embryo at the gestational age of 25-33 weeks were decalcified in 0.25 mol/L EDTA until Ca2+ was undetectable in the solution, and then were dissociated by 4 mol/L guanidine hydrochloride. Characterization of the extracts included SDS-PAGE for its molecular weight and amino acid analysis. RESULTS: SDS-PAGE showed the relative molecular mass of the DPP to be 140 x 10(3), 125 x 10(3) and 76 x 10(3). Amino acid analysis revealed the DPP contained mainly Asp (41.2%) and Ser (28.5%). CONCLUSION: Dentin phosphophoryn can be extracted from human embryo by using 0.25 mol/L EDTA and 4 mol/L guanidine hydrochloride. Its relative molecular mass was determined to be 76 x 10(3)-140 x 10(3), and its constitution characterized by abundant Asp and Ser resembles that of DPP extracted from the teeth with immature apices.