During the 1980s it became clear that the chain molecular weight of titin/connectin is-3 MDa
(2, 2) and that single molecules span between the Z-and M-lines. The latter conclusion is
based primarily on the electron microscopy of myofibrils labelled with titin monoclonal
antibodies. The general pattern seen after such labelling is of a single stripe in each half
sarcomere (Fig. 1). However, different titin monoclonal antibodies give stripes at different
positions throughout this region. Since the antigen is available across each half sarcomere …