[Histonet] Luxol dyes

[Robert Krug]

Megan: 

Saw  Dr Kiernan's posting on Histonet.  I cannot tell you what the MBS 
stands for, but I can add a little insight into naming dyes.  Dyes are 
given trivial names in most cases.   This really means the person 
originating the dye may call the dye whatever they please.  At one time 
there were may have existed guidelines.  If such guidelines existed, no 
one seems to be familiar with the specifics at this late date.   Today we 
use scientific nomenclature with set conventions to name products such as 
1-Cyclohexyl-2-phyrrolidone.  Personally I prefer the trivial names.

In some cases the abbreviations come from the German dye industry - who 
were really pioneers in the field.

The SF in Light Green SF yellowish = SaureFarbstoff (German) = acid dye

English terms are also sometimes abbreviated

FCF in Fast Green FCF = For Coloring Food

There are a series of fluorescent dyes available such as PKH26, PKH67.  In 
this particular case I cannot be 100% sure, but the person who filed the 
patent on these dyes just happened to have the initials PKH.  Coincidence? 
 In this particular case I would guess that the 26th and the 67th attempts 
were keepers.

Naphthol compounds are often named Naphthol AS-MX phosphate or possibly 
Naphthol AS-BI phosphate.  The structures are evidently different, but no 
one I have talked to has been able to explain why one product is given as 
the AS-MX designation and the next product is AS-BI

If you look at Conn's Biological Stains, 9th Edition, you will find the 
text lists many more obscure synonyms - as compared to the 10th Edition. 
In previous years, companies often gave common dyes unique names.  They 
may have believed they gained some competitive advantage from this 
practice. Even today dyes may often go by more than one name.  Sometime 
this is done when the company markets to various industries.  If you are 
selling to the printing industry, you might name a dye XXXX.  If you 
market dyes for histological use, you might name a dye YYYY.  Today I 
believe the trend is for companies to sell the dye by the name given the 
most common product of commerce.  This is probably why fewer synonyms are 
listed in the 10th Edition. Synonyms however are here to stay.  Sodium 
thiosulfate is still referred to as hypo in older textbooks.  This is 
because "hypo" was the term used in photography.

One of the many useful functions served by the Biological Stain Commission 
was the creation of CI or Color Index numbers.  It really doesn't matter 
what a company names a dye.  If Product X and Product Y from competing 
companies have the same CI number, there is a good chance the dyes may be 
used in the same staining procedures.  If the dyes are Certified by the 
BSC, this gives even more indication the dye should be acceptable for use. 
 The CI number varies from the CAS number.  For the CAS numbers to be 
identical, the molecular structure should be identical.  Not so with Color 
Index numbers.

For example, Basic Fuchsin may be composed of 100% Pararosaniline, or a 
mixture of pararosaniline, rosaniline, magenta II and magenta III. The 
pararosaniline may be the chloride or the acetate form.   So although the 
blends may vary from manufacturer to manufacturer and possibly even 
between lot numbers for a specific manufacturer, the dye must perform in 
an acceptable manner to receive certification from the Biological Stain 
Commission. In the 10th Edition of Conn's, no CI number is assigned to 
Basic Fuchsin, although the individual homologs are given given unique 
homologs. The 9th Edition of Conn's assigned Basic Fuchsin the CI number 
for Pararosanline. The real test is how well the dyes perform in actual 
staining procedures. Anyone really interested in dyes for biological use 
should try to obtain a copy of the methods used by the Biological Stain 
Commission.  Analysis and testing of biological stains - The Biological 
Stain Commission Procedures  (Biotechnic & Histochemistry 2002, 77(5&6): 
237-275

Methylene Blue is another prime example for a dye which is composed of a 
series of closely related homologs.  However in this case Methylene Blue 
is assigned a Color Index number, as opposed to Basic Fuchsin which was 
not assigned a unique CI number in the 10th Edition of Conn's. Again the 
major homologs are assigned CI numbers.

Other dyes by comparison are relatively pure and may be almost 100% pure.  
However sometimes purity is not all.  Some of the impurities may be 
present/added/act as stabilizers. In the case of Nile Blue, the presence 
of Nile Red as a contaminant may be highly desirable.

For other dyes the formulations are constantly shifting, even though the 
name remains relatively constant.  Alcian Blue is a dye which has a 
tendency to explode during manufacture.  This has resulted in a constant 
tinkering with the method of production over the years.  The dye sold 
today was probably manufactured very differently than an Alcian Blue 
manufactured decades ago.  If the product of commerce continues to provide 
acceptable staining results in the methods commonly associated with Alcian 
Blue, the dye will be sold & certified as Alcian Blue. It would be 
impractical to give each slight variation in product a unique name or CAS 
number. Trying to perform a literature search would be made extremely 
difficult to almost impossible. 

Tradition methyl green has not been produced commercially for many years 
(35-45+ ?). The actual product of commerce today is ethyl green.  In this 
case methyl green and ethyl green are really not synonyms.   However 
because ethyl green may be used for the same purposes as methyl green, the 
product of commerce continues to be called methyl green - very much to the 
annoyance of Dr Kiernan :)

Hope this helps,

Best Regards,

Bob Krug
Sigma-Aldrich
St Louis, MO