What parameters to use in order to sonicate chromatin to an average of 1Kbp fragments using Covaris E220 (12X12cm tubes)?

I'm trying to sonicate chromatin from Raw cells (mouse monocytes) that were fixated with 1% formaldehyde. I'm following the Covaris TruChIP protocol for shearing and either get no shearing or...

22 October 2014 5,001 1 View