Technical Support FAQ


Technical Support FAQ


Which acrylamide/bis ratio should I use?


Typically, proteins are separated with 29:1 (3.3%) and 37.5:1 (2.6%) ratios. Small DNA fragments are separated using a 19:1 mixture (5%), i.e., sequencing gels.

The reasoning behind this is that at low %T, the higher %C makes the gel stronger. DNA gels are usually low %T, so 19:1 (5%C) makes for a stronger gel. At high %T, say 10 or 12%T, 5%C makes the gel brittle, and it breaks more easily. A lower %C makes the gel more elastic and flexible, without loss of strength. So use the %C that makes the gel easier to handle at that %T.

Note that %C changes the pore size only slightly as far as can be detected by the position of the bands on the gel. The total acrylamide %T causes noticeable changes in band patterns when increased or decreased. Please see the micrograph in Allen, Saravis, and Maurer, Gel Electrophoresis and Isoelectric Focusing, Walter de Gruyter, Berlin and New York, 1984, page 6, for an excellent illustration of this point.

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