DNA binding to silica

[Paul N Hengen]

Kay Junghanns (junghann at deep-thought.biologie.uni-freiburg.de) wrote:

> I have been purifying DNA using silica gel. I was wondering how the DNA
> binds to the resin. What kinds of interactions are involved, and why does
> a reduction in salt concentration cause the DNA to elute?
> Anybody know? How about you people at the biotech companies!

I searched very hard for an answer a year ago and only came up with this.
Unless there is more recent evidence that I am unaware of, this is still the
current thinking. Please let me know if you find a better explanation.

| In the presence of a chaotropic buffer composed of highly positively charged
| molecules, usually guanidine (aminomethanamidine), DNA molecules have very
| strong affinity for siliceous materials. Fine particles of diatomaceous earth
| and other amorphous forms of silicon dioxide possess many fine pores and,
| having a high surface-to-volume ratio, are therefore extremely absorbent.
| Although the exact nature of the electrostatic interaction between the DNA
| molecules and the silicon dioxide is not known, the association is strong
| enough to hold small fragments of DNA during vigorous flow washing.

@inproceedings{Hengen1995,
author = "P. N. Hengen",
editor = "A. M. Griffin
     and H. G. Griffin",
booktitle = "Molecular Biology: Current Innovations and Future Trends",
title = "Mini-prep plasmid {DNA} isolation and purification
     using silica-based resins",
publisher = "Horizon Scientific Press",
volume = "Part 1",
address = "Wymondham, U.K.",
pages = "39-50",
year = "1995"}

See this reference for details on what is thought to be the interaction of
DNA with glass: Hall, R. H. 1967. Partition chromatography of nucleic acid
components (isolation of the minor nucleosides). Meth. Enzym. 12A: 305-315.

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