What are the shearing conditions for a probe sonicator?
The efficiency of sonication will depend on the type of sonicator which you use, so it is necessary to optimize the conditions for your equipment. Try different conditions starting by the sonication for 3 x 30 seconds on ice. Allow a 30 seconds pause on ice between each pulsing session. Take care to avoid foaming. If the size of sheared chromatin is to big try to sonicate longer time.