Setting of chromatin extraction conditions for low-quantity of starting material. After pre-fragmentation of tissue from FFPE slides taken from the lung of a 9-month-old K-rasv12 transgenic mouse, total tissue lysate was divided in parts equivalent to the material present in the slide number reported in the figure (4, 2, 1, 0.5, or 0.25) and subjected to chromatin extraction. (A) Correlation between the number of FFPE slides used as starting material and the amount of isolated chromatin before (left panel) and after (right panel) DNA purification. (B) Evaluation of chromatin fragmentation by electrophoretic separation on 1.3% AGE followed by ethidium bromide staining of purified DNA. MKs, molecular weight markers.