MICROHETEROGENEITY OF HUMAN ALPHA-FETOPROTEIN

甲胎蛋白(AFP)是一种糖蛋白，由两个亚基组成。 组分与凝集素刀豆球蛋白A的亲和力 (Con A)。Con A非反应性AFP的百分比一直是 在怀孕期间的羊水中的含量显著降低 与神经管缺陷有关。人类AFP也已经被 显示为一系列或一族电荷同分异构体，每个 等电点不同的异构体。电荷微观非均质性， 以及其他糖蛋白在conA结合方面的差异 归因于碳水化合物结构的细微差异。 因为AFP表现出碳水化合物的微观异质性，所以它是 合理的假设是，在 神经管所致的conA非反应性甲胎蛋白比例 缺陷将反映甲胎蛋白等电点模式的变化。 常规采集的羊水标本等份 妊娠中期诊断性羊膜腔穿刺术 将会被使用。将密切关注胎龄。 在那里获得样本。甲胎蛋白总浓度 将通过特定的放射免疫测定法在每个样本中进行测定 (RIA)。将测定甲胎蛋白的电荷微观不均质性 通过对一等量的羊水进行层析聚焦， 根据等电点分离蛋白质的技术。《法新社》 柱的每一部分都将通过放射免疫分析进行测量。这个 免疫反应峰，对应于各种电荷 同分异构体，将被合并。碳水化合物的微观非均质性 羊水中的电荷异构体和天然甲胎蛋白将是 经ConA柱层析进一步鉴定。差异在于 正常甲胎蛋白和甲胎蛋白的电荷微观不均质性 不正常的怀孕将被比较。评选结果 提出的研究应该增加我们对生物化学的了解 人甲胎蛋白的特性与提高我们的产前能力 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.