Percolation Threshold of Kinetoplast DNA Networks

Kinetoplasts are chainmail-like networks of connected DNA loops: we are interested in how their connected topology affects their physical properties. Kinetoplasts have a loop of excess of DNA linkages their edges like the elastic band in a shower cap, but previous topological estimates did not account for this boundary loop. We intend to measure the deformation of kinetoplasts and their topology by measuring their percolation threshold: a critical point at which a sufficient number of links are removed from the structure and it is destroyed. Our numerical simulations based on lattice graphs indicate that the presence of an edge loop leads to two percolation thresholds. We probe the percolation threshold of Crithidia fasciculata kinetoplasts experimentally by staining them with YOYO-1 and examining their disintegration under bright light due to photo-induced double-strand breakage. We observe the outer loop or fragments thereof surviving after the breaks in the interior of each kinetoplast reach percolation, supporting our predictions. With this protocol we can study the mechanics of membranes with varied bending rigidity, and we observe that dynamics are slowed by link removal.