Solvent-induced Collapse Transition in Kinetoplast DNA sheets*

Kinetoplasts are complex DNA structures consisting of circles that are linked together to form a network which resembles chain-mail armor. There is theoretical interest in the behavior of 2D materials, including thermally-induced crumpling. Kinetoplasts can serve as a model 2D polymer where their size, as determined by optical fluorescence microscopy, can vary depending on solvent quality, where water serves as a good solvent and ethanol as a poor solvent. We aimed to observe the 2D version of the coil-globule transition by measuring diffusivity and radius of gyration of kinetoplasts as a function of ethanol concentration. We observed a transition in the kinetoplast's shape at around 60-70% ethanol in solution, below which they appear as curve membranes and above which they appear as compact globules. More quantitative measurements of duplicated kinetoplasts will allow precision measurements of the universal size scaling exponent as a function of solvent quality.