Treating cells with paraformaldehyde leads to the establishment of chemical cross-links between free amino groups. When the cross-links join different molecules, a latticework of interactions occurs that holds the overall architecture of the cell together. Commercial formaldehyde solutions are not recommended, because they lack the advantages of using a variable-length polymer, and the cells will simultaneously be fixed with the alcohol (usually methanol). - [Read Fixing Attached Cells in Paraformaldehyde Protocol]
Treating cells with paraformaldehyde leads to the establishment of chemical cross-links between free amino groups. When the cross-links join different molecules, a latticework of interactions occurs that holds the overall architecture of the cell together. - [Read Fixing Suspension Cells with Paraformaldehyde Protocol]
For cells grown in tissue culture, the most useful method of lysis is treating with detergents, as described in this protocol. Non-ionic detergents, such as NP-40, solubilize the plasma and intracellular membranes, break many weak intermolecular bonds, and solubilize most of the commonly studied protein antigens. RIPA lysis buffer may be used as a more rigorous extraction buffer to release all but the insoluble proteins of the cell and to break most weak noncovalent interactions. - [Read Lysing Tissue-Culture Cells for Immunoprecipitation Protocol]