Request info on semi-dry blotters :)

Toumy Guettouche tguettou at newssun
Wed Sep 11 14:10:48 EST 1996



On 11 Sep 1996, BroweC wrote:

> Dear Group,
> 
> Does anyone have any experiences using a semi-dry blotter?  How do the
> various companies compare (Bio-rad, Hoeffer, etc.)?  How does semi-dry
> compare with standard blotting?  Is stacking the gel sandwiches on top of
> one another to do multiple blots at once a problem?
> 
> Thanks for helping,
> Chris
> Browec at aol.com
> 
> 
HI,

the differences between semi-dry and conventional blotting are as follows:
1) semi-dry-blotting is usually faster than convent. blotting (1h-1h30min 
vs.3h-ON) .
2)for semi you need a lot less buffer, it generates less heat (low current), 
therefore you do not have to transfer in coldroom and you can use a conventional 
powersupply.
3)you can transfer multiple gels (up to 6 in some systems) at the same time.
4) conventional blotting usually transfers higher molecular weights 
better than does semi ( Methanol content of some semi buffer)
but in semi you get more even bands and usually no distortions.
That is basically all I remember.
Now to the semi dry units I worked with.
I did work with the Pharmacia Novablot semi dry unit. It gives very good 
results with the discontinous buffer system. The problem is it uses 
Graphite plates that shed graphite and go bad after 2 years(in my case) 
of extensive use. Also it is very expensive (ca. 900$; after all it's from 
Pharmacia) and some parts break easily (e.g the connectors of the 
electrodes to the plates.). Sometimes you also get "bubbles" on your 
blot, because of electrolysis an hence gas bubbles that get trapped an 
inhibit transfer in your stack.
Now I am using a Hoeffer(now Hoeffer-Pharmacia) TE77 unit that gives also 
very good results. 
However, you do not get gas bubbles, since they use plates with a mesh, 
so the gas gets released from the stack. There plates also will last a 
lot longer, since they are coated with platinum. The unit is sturdier, so it 
can probably withstand more abuse.
However, this unit is also very expensive (ca. 900$).
Schleicher&Schuell has a unit that seems to be ok as well. It uses plates 
that do not get used up and has also a sturdy design. Unfortunately it is 
smaller than the other two units.
The best about it is the price, it is only around $500.
I never tested Biorad or any other company that sells semi dry blotters.
For literatur on semi dry-blotting:
check 
Bjerrum, Ole j., Larsen, K., and Heegaard, N. (1988) CRC Handbook of 
Immunoblotting of Proteins Vol1,CRC press.

Hope that helps

Toumy




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