I remember from an obscure source that some restriction enzymes are very
unstable at incubation conditions, dying out after 30 min or so,
however, my latest NEB catalog does not say this about AluI. NEB sells a
recombinant enzyme, which could be more stable. It is also possible that
your Alu I preparation is from the original bacteria and contains some
additives that trap DNA in the well. The way to check this is:
1. To digest a plasmid DNA and load it in an SDS containing buffer after
heating at 65 C.
2. Phenol extract the digest before loading ( phenol phase can be loaded
without precipitaion of DNA, just add the usual dye ).
Hope this helps,
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Alexander Kraev, PhD Internet: kraev at bc.biol.ethz.ch
> Lab.of Biochemistry III Phone: 0041-1-632-31-47
> Swiss Federal Inst. Of Technology FAX: 0041-1-632-12-13
> Universitaetsstr. 16 URL: http://184.108.40.206/kraev.html/> CH-8092 Zurich