poly-L-Histidine (Sigma P9386, MW 5000 to 15 000 Daltons)

Michael Witty mw132 at mole.bio.cam.ac.uk
Fri Jul 27 15:54:06 EST 2001

Dear All,
        I am using this product as a positive control in a blot with a his
tagged protein BUT I have noticed a few things about it that puzzel me.  I
thought that it would act just like a protein, so I tried dissolving 10mg
in 1ml water.  No dissolution.  Then I tried adding acid to 1M (later the
Sigma help people told me 0.1M was what they used).  It dissolved quickly.
BUT when I added 10 micolitres to 5 microliters of my 3x protein loading
buffer there was immediate precipitation.  I heated the sample and loaded
my PAGE gel anyway, then stained the eppendorf tube - it turned blue at
the bottom.

Soooooo, how does a person dissolve poly-L-Histidine and once dissolved
how does a person mix it with SDS without precipitation.  I hate to misuse
a reagent and loose most of it to precipitation.

(the Coomassie blue stained duplicate gel showed a broad 5kDa band so not
all was lost).

Regards, Mike.

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