[Histonet] Melanin and Azure B

[John A. Kiernan]

If the pigment is already black, it doesn't need
to be stained. Melanin is bleached by 3% hydrogen
peroxide ("10 volumes available oxygen"), 3 to 36
hours at room temperature. (Control slide in
water.) Bleaching by H2O2 is considered a
reasonably specific test for melanin. 

Lillie & Fullmer (p.524) comment that melanin is
stained dark green by 0.05% azure A at pH 1 for 20
min. This coloration resisted methylation, so it
may be due to oxidized cystine in an associated
protein. 
-- 
-------------------------------
John A. Kiernan
Department of Anatomy and Cell Biology
The University of Western Ontario
London,   Canada   N6A 5C1
   kiernan[AT]uwo.ca
   http://publish.uwo.ca/~jkiernan/
   http://instruct.uwo.ca/anatomy/530/index.htm
_______________________________
Jackie M O'Connor wrote:
> 
> Hi -
> I found a couple of old posts about being able to stain melanin with 1%
> aqueous Azure B.  Can someone shed light on why this isn't seeming to work
> for me?
> I'm basically trying to identify a black pigment in FFPE that looks like
> melanin without having to depend on HMB45.  Any takers?
> 
> Jackie
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