Buffer and Extraction Buffer- Definition, Components, Significance


An extraction buffer is a type of buffer solution that is used to break open cells and release their contents for further analysis. Buffer solutions are mixtures of weak acids and their conjugate bases, or weak bases and their conjugate acids, that resist changes in pH when small amounts of acid or base are added. By maintaining a constant pH, buffer solutions help to preserve the structure and function of biological molecules, such as proteins and nucleic acids, that are sensitive to changes in acidity or alkalinity.

Extraction buffers are designed to lyse (break open) cells by disrupting their membranes and solubilizing their components. Lysis can be achieved by physical methods, such as grinding, sonication, or freeze-thawing, or by chemical methods, such as detergents, chaotropic agents, or enzymes. The choice of lysis method depends on the type of cell and the target molecule of interest. For example, bacterial cells have a tough cell wall that requires mechanical or enzymatic lysis, while animal cells have a more fragile membrane that can be lysed by mild detergents.

The composition of an extraction buffer depends on the purpose of the experiment and the properties of the target molecule. Different extraction buffers may contain different salts, pH adjusters, reducing agents, enzyme inhibitors, substrates, cofactors, chelators, stabilizers, or preservatives. These components help to optimize the yield and quality of the extracted molecules by preventing degradation, aggregation, oxidation, precipitation, or contamination. Some examples of common extraction buffers are:

  • RIPA buffer: A detergent-based buffer that lyses most types of cells and solubilizes proteins and nucleic acids. It contains sodium chloride (NaCl), tris(hydroxymethyl)aminomethane (Tris), sodium deoxycholate (SDC), sodium dodecyl sulfate (SDS), ethylenediaminetetraacetic acid (EDTA), and phenylmethylsulfonyl fluoride (PMSF).
  • Tris-EDTA (TE) buffer: A mild buffer that preserves nucleic acids by chelating metal ions that can catalyze nuclease activity. It contains Tris and EDTA.
  • Phosphate-buffered saline (PBS): A physiological buffer that mimics the osmolarity and pH of biological fluids. It contains sodium phosphate (Na2HPO4), sodium chloride (NaCl), and potassium chloride (KCl).
  • Tris-buffered saline (TBS): A similar buffer to PBS but with Tris instead of phosphate. It is often used for immunological assays.
  • Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) sample buffer: A buffer that denatures proteins and coats them with negative charges for electrophoretic separation. It contains Tris, SDS, glycerol, bromophenol blue (a dye), and dithiothreitol (DTT) or b-mercaptoethanol (BME) as reducing agents.

In summary, an extraction buffer is a buffer solution that is used to break open cells and release their contents for further analysis. It helps to maintain a constant pH and to protect the extracted molecules from degradation or loss of activity. Different extraction buffers have different compositions depending on the type of cell and the target molecule of interest.