MICROHETEROGENEITY OF HUMAN ALPHAFETOPROTEIN

甲胎蛋白（AFP）是一种糖蛋白，由两个亚基组成， 相对于其对凝集素伴刀豆球蛋白A的亲和力， (con A）。 已将Con A非反应性AFP的百分比 在怀孕期间羊水中的含量明显较低 与神经管缺陷有关 人类AFP也被 显示作为一系列或一族电荷异构体存在， 等电点不同的异构体。 电荷微观异质性， 以及其他糖蛋白在con A结合上的差异， 这归因于碳水化合物结构的细微差异。 由于AFP具有碳水化合物微异质性， 可以合理地假设， 由于神经管引起的con A非反应性AFP的比例 缺陷将反映AFP等电模式的变化。 常规检查期间获得的羊水样本等分试样 妊娠中期诊断性子宫内膜穿刺术 将用于 将仔细注意胎龄 在该温度下获得样品。 AFP总浓度 将通过特异性放射免疫测定法测定每份样本中的 （RIA）。 将测定AFP的电荷微观异质性 通过对羊水等分试样进行色谱聚焦， 根据pI分离蛋白质的技术。 法新社在 通过RIA测量柱的每一级分。 的 免疫反应性峰，对应于各种电荷 异构体，将合并。 碳水化合物的微观异质性 羊水中的电荷异构体以及天然AFP将 通过con A柱色谱进一步评估。 差异 正常人和正常人AFP的电荷微异质性 将比较异常妊娠。 的结果 拟议的研究应该增加我们对生物化学的了解， 人AFP的性质，提高我们的产前诊断能力， 出生缺陷的诊断。

Alphafetoprotein (AFP), a glycoprotein, consists of two sub- fractions with respect to its affinity for the lectin concanavalin A (con A). The percentage of the con A non-reactive AFP has been shown to be significantly lower in amniotic fluid from pregnancies associated with neural tube defect. Human AFP has also been shown to exist as a series or family of charge isomers, each isomer differing in isoelectric point. Charge microheterogeneity, as well as differences in con A binding, of other glycoproteins has been attributed to subtle differences in carbohydrate structure. Because AFP exhibits carbohydrate-microheterogeneity, it is reasonable to assume that the differences observed in the proportion of con A non-reactive AFP as a result of neural tube defect will reflect changes in the isoelectric pattern of AFP. Aliquots of amniotic fluid samples obtained during routine diagnostic amniocentesis in the second trimester of pregnancy will be used. Careful attention will be paid to the gestational age at which the sample is obtained. The total concentration of AFP will be determined in each sample by specific radioimmunoassay (RIA). The charge microheterogeneity of AFP will be determined by subjecting aliquots of amniotic fluid to chromatofocusing, a technique which separates proteins according to pI. The AFP in each fraction of the column will be measured by RIA. The immunoreactive peaks, corresponding to the various charge isomers, will be pooled. The carbohydrate-microheterogeneity of the charge isomers as well as native AFP in amniotic fluid will be further assessed by con A column chromatography. Differences in the charge microheterogeneity of AFP between normal and abnormal pregnancies will be compared. The results of the proposed study should increase our knowledge of the biochemical properties of human AFP and improve our ability for prenatal diagnosis of birth defects.