Purification of DNA Fragments from Agarose Gels Using Glass Beads

Size selection of DNA fragments is frequently required before ligation or labeling for the preparation of probes. Many methods are available for purifying DNA fragments following electrophoresis in agarose gels, including the use of low-melting agarose, electrophoresis onto DEAE-cellulose paper, electroelution (with many variations), and usage of various DNA binding matrices. The following method is based on the capacity of sodium iodide (NaI) to dissolve agarose gels and the binding of DNA to glass surfaces at high salt concentration. A very high DNA binding capacity is achieved by using a fine powder of crushed glass. After washing, the DNA can be readily eluted from the glass in water, at a final concentration of up to 100 �g/mL.