MICROHETEROGENEITY OF HUMAN ALPHAFETOPROTEIN

Project: Research project

Project Details

Description

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.
StatusNot started

Funding

  • National Institutes of Health
  • National Institutes of Health: $138,809.00
  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health

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