About ten days ago I posted a question on DAB precipitate. Right after that
we had  network system problem and two days worth of email was never
delivered. So not only I cannot thank you for your, as usual, informative
replies but I still don't have the answer. I am posting my question again.
Sorry for the inconvenience.

Dear colleagues,
Would you know why does the DAB solution precipitate  when applied on the
tissue.  I have been always using Vector DAB kit. This usually happens when
the staining is done, so it doesn't  interfere with the results. I  wash my
sections with PBS before applying the DAB solution. I have just lent the kit
to someone else to use. She apparently washed her samples with dH2O before
applying the DAB and it precipitated immediately, without staining. Is it pH
sensitive? Also, a while ago I washed my sections with Tris buffer before
the DAB application and that gave me background.  Could you help me
understand?
Thank you,
Lilith
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Lilith Ohannessian-Barry
National Research Council
Institute of Biological Sciences
CANADA
Tel;613-993-6460
Fax;613-941-4475
e-mail; lilith.barry@nrc.ca