Bio-Rad AG® MP-50 Cation Exchange Resins - Manual (Page 3)

Section 1
Introduction
Ethidium bromide is used to visualize DNA and
RNA preparations because it intercalates between the
bases and fluoresces when irradiated with UV light at
300 nm. Propidium iodide, which also intercalates
between bases, is used to increase the separation of
superhelical and non-supercoiled DNA in cesium
chloride gradients. Molecular Biology Grade AG 50W-
X8 cation exchange resin is useful for removing these
dyes, to provide a purified plasmid preparation. The
resin is certified to be free of endo-and exo-nuclease,
and ligase inhibitors. The resin has a high selectivity for
the hydrophobic, cationic ethidium and propidium ions
and repels the strongly anionic nucleic acid. The
fluorescent labeled DNA is passed over a column of the
Molecular Biology Grade AG 50W-X8 cation exchange
resin, which removes the fluorescent dye from the DNA
or RNA. The pure plasmid preparation is then collected
in the void volume.
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