magic mp & sequenase

gagnon at gagnon at
Sat Dec 5 03:20:37 EST 1992

Earlier in this discussion
>>>What is the binding matrix of the Promega mini-prep column used in this kit?
>>In my mind the earlier protocols claimed the 'magic' resin to "..more effective
>>than other silicon-based media..". Nevertheless, I have found self-
>>prepeared glassmilk + 7M guanidinium chloride + Promega protocol to
>>work in my hands exactly as well as the original 'magic' resin. Since Gn.HCl is
>>more convenient to work with than NaI (it is light insensitive, can be stored
>>at RT) I have been using this combined protocol since then. Therefore, though
>>the 'magic' resin itself does not seem to be powdered silica, it can be
>>with it. My guess is that the 'magic' is silica gel since protocols utilising
>>this reagent have been launched by other manufacturers.
>>       armin sepp
>>       asepp at
>Could you please provide me with where and what type of silica gel or
>glass you use and your procedure for prepping it up. thanks a lot.
> Michael Benedik                                INTERNET: Benedik at

Protocol for preparing glassmilk (combined from the protocols presented earlier 
this year in the same newsgroup) 

Glassmilk is 50% v/v slurry of acid washed powdered silica in water.
1) Resuspend 50g silica powder, eg. Sigma S-5631 (not fumed silica that is too
fine) in 200 mls of water, stir for 1h and take the fraction that settles
between 2 mins and 60 mins.
2) Boil the settled material for 1 hour in 10 volumes of 50% nitric acid and
wash extensively with several changes of water (6-7 times) until pH of the wash 
is back to ca 6.
3) After final spin, resuspend in equal volume af water. Store in 1ml aliquotes 
at -20 or -70.
4) Thaw before use and resuspend carefully. Use 2 microliters per micrgogram 
of DNA.

Some remarks. 
0) The yield from the above precure was ca 20 ml of glassmilk.
1) I do not know how stable glassmilk is at room temperature,
alone or when mixed with Gn.HCl. I have always stored the stock of glassmilk 
at -20 (no changes in properties in half a year, sofar) and mixed it fresh 
with Gn.HCl before use.
2) The same glassmilk can be used to extract DNA from TAE agarose gels 
when you dissolve the gel slice in 7M NaI.
3) I haven't tried to use silica gel to prepare glassmilk. Should anybody try,
it would be interesting to know the results.

	armin sepp
	asepp at

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