Hi,
    The blocking is put on just before the primary antibody then it is drained
or blown off (not rinsed). I agree the directions are vague. One might think it
is before H2O2 or for that matter before epitope retrieval. By the way it is
used after enzyme predigestion if you are using that.
Amos Brooks

Sonia Greco wrote:

> Dear Histonetters,
>
> I just bought the DAKO Biotin Blocking System, which suggests to use before
> application of the first step of the staining procedure. Does this mean
> after the secondary antibody, before a strepABC and DAB staining. or do I
> apply it before between the primary and secondary antibodies?
>
> Also: I am doing immunohistochemistry with a polyclonal goat anti human
> antibody. For a negative control, I would have liked to use a goat
> non-immune IgG, but didn't have any, so I have used normal goat sera. Would
> you know the best dilution to use to make it a good negative control?
>
> Thanks in advance
>
> Sonia
> QIMR, Australia