This is an illustration of the three dimensional shape of an immunoglobulin (antibody) protein. It is a "Y"-shaped protein, composed of three fragments, two Fab fragments (the "arms" of the Y), and an Fc fragment (the "stem" of the Y). These are joined by a hinge region, which is not shown here. The illustration is an "artist's impression" based on the crystal structures of separate Fc and Fab fragments. Here is a Java applet to display these in 3-D. Once the applets are loaded (this may take some time), you can move the structures with your mouse.
The Fab fragments are made up of two chains of amino acids, a "heavy" chain (dark red and dark blue) and a "light" chain (light pink and light blue). The Fc fragment is made up of two "heavy" chains (dark and light green). In the VSNS BioComputing Course students study the similarities between these "heavy" and "light" chains by using sequence alignment software on the World Wide Web.
The antibody figure was prepared using UCSF MidasPlus