DNA recovery is the laboratory process of isolating and purifying intact DNA fragments following extraction, enzymatic digestion, PCR amplification, agarose gel electrophoresis, or library preparation.
Primary Methods for DNA Recovery
- Silica-Membrane Spin Columns: Utilizes chaotropic salts (such as guanidine thiocyanate) to dehydrate the phosphodiester backbone, promoting selective DNA adsorption onto silica matrices under low pH. Following ethanol washes to remove salts and proteins, purified DNA is eluted in low-salt, alkaline buffer (10 mM Tris-HCl, pH 8.5) or nuclease-free water.
- Magnetic Bead-Based Separation (SPRI): Carboxylated or silanized paramagnetic beads bind DNA reversibly in the presence of polyethylene glycol (PEG) and NaCl. Enables automated high-throughput size selection and purification with high recovery efficiencies.
- Gel Extraction: Specific target DNA bands are excised from agarose gels following electrophoresis, melted in chaotropic dissolving buffers, and processed through spin columns to eliminate agarose polymers, ethidium bromide / intercalating dyes, and primers.
- Ethanol / Isopropanol Precipitation: Classical method employing monovalent cations (sodium acetate, ammonium acetate) and cold alcohol to precipitate nucleic acid polymers out of aqueous solution, followed by high-speed centrifugation.
Assessing DNA Quality and Yield
Spectrophotometric absorbance ratios evaluate sample purity:
- A260/A280 Ratio: Pure double-stranded DNA exhibits a ratio between 1.8 and 2.0. Ratios significantly below 1.8 indicate residual protein or phenol contamination.
- A260/A230 Ratio: Values between 2.0 and 2.2 indicate absence of chaotropic salts, carbohydrates, and organic solvents. Ratios <1.8 suggest salt carryover that may inhibit downstream PCR polymerases.
Browse microcentrifuges, spectrophotometers, and gel documentation systems on the IBS Product Catalogue.
