Ultrastructure of Secretory and High-Polymer Serum Immunoglobulin A of Human and Rabbit Origin

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Science  15 May 1970:
Vol. 168, Issue 3933, pp. 847-849
DOI: 10.1126/science.168.3933.847


Electron micrographs of immunoglobulins A from human and rabbit colostrum, which were purified on tall agarose columns, revealed Y-shaped molecules (125 by 140 angstroms). The linear dimensions of the arms were 55 to 75 by 25 to 30 angstroms. A molecular model is postulated in which two immunoglobulin A monomers are superimposed on each other in a close-packed state with the secretory piece inserted in the constant region of the α-chains. High-polymer (11 or 13S) immunoglobulin A molecules (total span 100 to 110 angstroms) from human serum were composed of four arms (50 to 55 by 20 angstroms) joined at a contrast-rich center.

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