Transmission electron micrographs of negatively contrasted digestant removed from the clots. Pieces of fibers, protofibril aggregates, and smaller fragments observed in the supernatants. Arrows indicate areas that are darker as a result of removal of protein by digestion. Arrowheads point out brighter areas where stain was excluded because of plasmin binding. (A) Fiber surrounded by lacy meshwork of protofibril-like structures. (B) Fiber surrounded by meshwork made up of protofibrils and other smaller structures. (C) Fiber splayed into bundles of protofibrils. Bar for (A) through (C) equals 0.5 μm. (D) Fiber showing sharply cut end (at right) and another chunk that is largely separated from the rest of the fiber but still associated with it (asterisk). (E) Digested fiber with missing pieces and truncated end; note some smaller fragments in the background. (F) Piece of remaining fiber where individual protofibrils can be visualized. (G) Very thin fiber remnant with other smaller fragments. (H) Small fragments present at longer times of digestion or with higher plasmin concentrations. Some examples of DDE complexes are circled. Bar for (D) through (H) equals 0.1 μm.