What are the common fixatives for ChIP experiments?

Common fixatives for ChiP experiments include formaldehyde, alcohols, and acrolein. 

1. Formaldehyde is the most commonly used fixative in ChIP experiments. Formaldehyde is commonly used to create reversible cross-links between proteins and DNA or between proteins themselves within chromatin. This cross-linked chromatin is then broken into smaller fragments, and protein-DNA target complexes are isolated using specific antibodies through immunoprecipitation. The timing of formaldehyde cross-linking is crucial for achieving a proper signal-to-noise ratio. 
2. Methanol and ethanol are commonly used alcohols for fixing cells and tissues. They replace water molecules in tissues, causing proteins to precipitate at their isoelectric points. Although alcohols can stabilize the secondary structure of proteins, they may not preserve tissue morphology and penetrate as well as formaldehyde-based fixatives. Alcohols are mainly used for fixing frozen tissue sections and cells, particularly for membrane surface antigens.