What kinds of immunoprecipitation procedures exist?

There are 4 main types of immunoprecipitation procedures. 

• Individual protein immunoprecipitation (IP) – IP is the simplest form of immunoprecipitation. It is used to isolate a single protein from a solution containing several different proteins. It involves using an antibody that is specific to a known protein. The aim is to study the isolated protein’s identity, structure and expression as well as its activation or modification state. 
• Protein complex immunoprecipitation (Co-IP) – Co-IP is used to isolate intact protein complexes from a solution. This process involves using an antibody that is specific to a known member of the protein complex, making it possible to pull the entire protein complex out of the solution. Targeting the known protein with an antibody enables researchers to identify the unknown members of the protein complex. Molecular biologists use this technique to study protein-protein interactions. 
• Chromatin immunoprecipitation (ChIP) – Chromatin immunoprecipitation is used to immunoprecipitate the protein-DNA complex out of cellular lysates. The in vivo nature of this technique sets it apart from the other types of immunoprecipitation procedures. The aim of ChIP is to study protein-DNA interactions that occur inside the nucleus of living tissues or cells. It is commonly used to monitor transcriptional regulation. 
• Ribonucleoprotein immunoprecipitation (RIP) – RIP is similar to ChIP. The only difference between the two is that RIP is used to immunoprecipitate the protein-RNA complex. It involves using an antibody targeting the ribonucleoproteins of interest. RNA can be extracted from the purified RNA-protein complexes and analyzed further by RT-PCR or cDNA sequencing.