John Mundy’s laboratory at the University of Copenhagen has written up protocols for Coimmunoprecipitation (co-IP) of Nuclear Proteins and Chromatin Immunoprecipitation (ChIP) from Arabidopsis in the September issue of CSH Protocols. co-IP is useful for identifying and isolating protein-protein interactions and protein complexes. ChIP allows the analysis of protein-DNA interactions, and is a technique currently seeing widespread use as the field of transcriptional regulation continues to make great advances. One advantage to this set of techniques is that the nuclear lysis buffers standard in most protocols for plant nuclear protein extraction are incompatible with co-IP. Here, nuclear protein extraction is accomplished via sonication in co-IP buffer and treatment with Benzonase, which results in material that can be used with co-IP.