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Dialysis (using dialysis tubing)

Molecularpourous membrane tubing is used for desalting, protein and DNA isolation / purification. It comes in several diameters and pore sizes (for molecular weight conversions for nucleic acids see general reference).

The brand used in M. Soares Lab is Spectra/Por produced by Spectrum Medical Industries, Inc.(60916 Terminal Annex, Los Angeles, California 90060, Phone: (213) 650-2100, (800) 634-3300), distributed by Fisher. Several molecular weight cut-offs and diameters are available. Spectrapor tubing comes either wet (ready to use) or dry.

Prior to use of dry membranes:

  1. Wash 30 minutes at 60C in a large volume (1000x) of 2% sodium bicarbonate and 1 mM EDTA)
  2. Rinse tubing thoroughly with distilled water.
  3. Cool and store at 4C in either 1% formaldehyde, 1% sodium benzoate, or 0.1% sodium azide, deionized water, or 100% ethanol. Keep the tubing completely submersed. Uncleaned membranes can be stored at room temperature.
  4. Do not autoclave. Heating over 80C changes the membrane characteristics (drop permeability).
  5. To prevent sticking of DNA or charged proteins to the membrane, coat wet tubing inside and out with a solution of 0.05% BSA in 1 x TBE buffer.
  6. The pH range for membranes is 2 - 12.