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:
- Wash 30 minutes at 60°C in a large volume (1000x) of 2% sodium bicarbonate and 1 mM EDTA)
- Rinse tubing thoroughly with distilled water.
- Cool and store at 4°C 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.
- Do not autoclave. Heating over 80°C changes the membrane characteristics (drop permeability).
- 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.
- The pH range for membranes is 2 - 12.