Structure and function of bovine colostral lactoferrin

1.乳铁蛋白的分子量、糖含量和二级结构经SDS聚丙烯酰胺凝胶电泳测得乳铁蛋白的分子量为81，800 ± 2，600。中性糖的碳水化合物含量为8.8%，氨基糖的碳水化合物含量为2.7%。由圆二色谱计算出螺旋含量为24%.乳铁蛋白与蓝色染料的相互作用研究牛乳铁蛋白与固定化Cibacron Blue F3 GA柱有很强的相互作用。有人认为，这种相互作用是由于强静电力。用胰蛋白酶消化乳铁蛋白后，得到分子量为52 KD和27 KD的片段。固定化蓝染料亲和层析结果表明，分子量较大的片段既能与蓝染料结合，又能与铁离子结合。将分子量为20 ~ 40 KD的抗乳铁蛋白片段吸附到固定化抗乳铁蛋白血清柱上.碳水化合物部分的组成和结构的估计碳水化合物部分通过肼解释放，然后通过离子交换色谱分离成中性和酸性糖部分。用气相色谱法测定了它们的糖组成。固定化的内链孢霉糖苷酶也用于切割乳铁蛋白中的碳水化合物部分。进行酶凝集素测定以估计碳水化合物链的组成和结构。

1. Molecular weight, sugar content and secondary structure of lactoferrin Molecular weight of lactoferrin was estimated to be 81,800+2,600 by SDSpolyacrylamide gel electrophoresis. Carbohydrate contents were 8,8 % for neutral sugar and 2.7 % for amino sugar. Helical content was 24 % calculated from CD spectrum.2. Interacting properties of lactoferrin with blue dye Bovine lactoferrin showed strong interaction with immobilized Cibacron Blue F3GA column. It was suggested that such interaction has been due to the strong electrostatic forces.3. Tryptic fragments of lactoferrin After digestion of lactoferrin by trypsin, fragments of which molecular weight was 52 KD and 27 KD were obtained. By the affinity chromatography with immobilized blue dye, the fragment of larger molecular weight showed the binding ability both to blue dye and iron. Onto the immobilized anti-lactoferrin serum column, the fragments of which molecular weights were from 20 to 40 KD, were adsorbed.4. Estimation of composition and structure in carbohydrate moiety Carbohydrate moieties were liberated by hydrazinolysis and then were separated into neutral and acidic sugar moieties by ion exchange chromatography. They were estimated on their sugar compositions by gas chromatography. Immobilized endoblycosidases were also used to cleave the carbohydrate moieties in lactoferrin. Enzyme lectin assay was done in order to estimate the composition and the structure of the carbohydrate chains.