There are several ways to stain -SH groups, of
varying sensitivity and specificity. Two that I
have used and would recommend are:

1. Acidified permanganate followed by alcian
   blue, pH 1 or lower. Rather low sensitivity,
   so there's little background, but sulphated
   mucosubstances also stain (do a control
   alcian blue without prior oxidation).
   This the method of Adams & Sloper 1955
   Lancet I:651-652, but with permanganate
   oxidation instead of performic acid, which
   is nasty stuff. I think the first publication
   of the modification was Pasteels &  Herlant
   1962 Z. Zellforsch. 20-39. 
2. The ferric ferricyanide reaction. High
   sensitivity, but other reducing groups
   also react (see Lillie & Donaldson 1974
   Histochem. J. 6:679-684). The prussian blue
   product fades with time (a few years) in
   some mounting media, so take photos.

Another simple reagent is mercurochrome
(20 mg in 0.5ml water, then add 100 ml
of N,N-dimethylformamide). Stain 1  hr
for green fluorescence, or 48 hr for red
staining of -SH groups. After staining
wash in 3 changes of DMF, 2 each of ethanol
& xylene, and mount with a non-fluorescent
resinous medium. 

Lillie & Fullmer's 1976 textbook is a good
source for methods of this kind.
-- 
-------------------------
John A. Kiernan
Department of Anatomy and Cell Biology
The University of Western Ontario
London,   Canada   N6A 5C1
   kiernan@uwo.ca
   http://publish.uwo.ca/~jkiernan/
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owen.lewis@utoronto.ca wrote:
> 
> I was wondering if anyone knew of a stain that would target SH groups.
>  I'm trying to stain hyaluronan that's been thiolated and I'm finding
> that alsian blue is very faint.  Is there a way to go after the sulfur
> groups??
> 
> thanks,
> Owen Lewis
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