why they use isopropanal for precipitate DNA in midiprep - (Feb/22/2010 )

I just to know (in midiprep) why they use isopropanal for precipitate DNA before and clen with 70% alcohol
why they did not use alcohol for precipitate DNA

You can use either, you just need to adjust the volumes accordingly. I use 3 vol ethanol or 0.8 vol isoprop (although some people use 1 vol....)
I've been told that it is because isoprop is more efficient at precipiting DNA (hence the lower volume required).

And the isopropanol evaporates much more slowly, so you want the final wash to be in ethanol rather than in isopropanol. The important factor is most likely the capacity of the tube the DNA happens to be in when it is time to precipitate it.

One reason is the volume required to precipitate using ethanol is much larger than with isopropanol.

thanks you so much for all suggestion
and I would like to know property of TEMED and 10% APS in SDS-PAGE

catalysts for the crosslinking reaction.