dextran sulfate-- a cheaper source??

h9290184 at h9290184 at
Mon Apr 11 23:42:09 EST 1994

In article <Cnt28w.IuG at>, mman at (Michael Man) writes:
>  	I use dextran sulfate in my hybridization solution.  It gives me very 
> good results, but it is too expensive, $732 per 500 gms from Sigma.  Does 
> anyone know a cheaper place to go?  Thanks for your help.
> 	Also I will be very grateful if you can suggest an alternative way 
> to prepare prehyb. and hyb. solution.  I use GeneScreen transfer membrane and
> UV-crosslink RNA. 
> Michael
> mman at

Hi there,
Sometimes ago in 1989 at UCSF, I mentioned dextran sulfate in my hyb solution
to someone in the next door lab, he answered me with "Do you have dinosaurs for
pets at home?" That was before Jurassic Park. 
I now use 7% SDS and .25 M Na2HPO4 pH7.2 for my prehyb and hyb solution and
nothing more for all my blots (north/south-erns) or colony/plaque screening for
all nylon membranes only  not for nitrocelulose.
Make a 2X solution of SDS ie 14% and  a 2x solution of Na2HPO4 ie .5M
Mix equal volume of each and prehybe at 65 degree for at short as 15 minutes to 
2 hours then hybridize also at 65 degree any lenght of time (you can then
follow your own routine for the hyb time and wash etc.)

14% SDS   140 grams SDS  in H2O to 1 liter.
.5M Na2HPO4  134 grams of Na2PO4.7H2O(MW:268.07) + H2O + 4 ml 85% H3PO4 per
liter. H3PO4 is Ortho-phosphoric acid it comes as a 85% solution.

I got the recipe from the instruction manual of Zeta-Probe from BioRad. 
Usual disclaimer apply. The reference they cite is:Churh GM et al., PNAS
81,1991 (1984).
So far (IMHO) it's the easiest, cleanest, cheapest(?) prehyb/hyb solution I
have seen.
I will be happy to hear of a even better one, please post if any.

Kaimin Chan
the Institute of Molecular Biology
the University of Hong Kong
Hong Kong
H9290184 at

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