Dima Klenchin klenchin at facstaff.REMOVE_TO_REPLY.wisc.edu
Mon Nov 27 17:18:55 EST 2000

Michael Witty <mw132 at mole.bio.cam.ac.uk> wrote:
:Does anyone have experience making their own hydroxyapatite?  I have had a
:go at mixing calcium and phosphate salts to get a precipitate, but this
:did not bind any protein.  When I look calcium phosphate up in the Merck
:index I see there is more than one kind - how do I know if I am obtaining
:hydroxyapatite and not another form of calcium phosphate?  Mike.

I am not sure why you'd want to make it yourself. Commercial one
is not that expensive. I particularly like Bio-Rad's "ceramic HA". 
Since it flows very fast and the column basically never needs to
be repacked, it beats regular HA easily. 

You made CaHP04.2H20 while HA is really Ca5(PO4)3.OH

Here is the "classic" protocol:

        Pakroppa et al., PNAS, 1974, 71:699-703
Equal volumes of CaCl2 and Na2HPO4 (0.5 M each)
are simultaneously and quickly poured into beaker 
with stirring bar going very fast. The precipitate is washed,
filtered, resuspended in hot water + 10% concentrated
ammonia and boiled for 30 min. Then washed thoroughly
again with water then 10 mM phosphate, pH 7.1, 
first at room temp, then at 90C, then rt again. 
Define and store. 

You might also check:

Mazin et al., Anal Biochem, 1974, 61:62-71
Hirano et al., ibid, 1985, 150:228-234


        - Dima

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