Nonidet P-40

Curt Ashendel ashendel at
Mon Apr 3 10:26:03 EST 1995

On 31 Mar 1995 23:41:00 GMT, 
Steve Danko  <sdanko at> wrote:

>>  Nonidet P-40 is the same as Triton X-100, which is a common nonionic
>>  detergent used in many extraction protocols to solubilize membranes, very
>>  good for nuclear membranes. As already somebody stated, it has a polar
>>  polyethylenglycol chain and a  non-polar tail to interact with membranes,
>>  leading to the formation of lipids trapped in water-soluble micelles.
>Nonidet P-40 is ethylphenolpoly(ethyleneglycolether)n
>Triton X-100 is octylphenolpoly(ethyleneglycolether)n
>Both are nonionic surfactants.
>Both are available from Berhringer Mannheim or Sigma.
>For more info, ask Boehringer Mannheim for their free booklet:
>"Detergents for Membrane Research".

Sorry, but I think Boehringer is wrong about this.  Their discussion of 
detergents in their 1995 catalog also erroniously indicates that Nonidet 
P40 lacks a phenol group and so does not absorb in the UV wavelengths. They 
need better Tech info QC.

Sigma, Pierce, and CalBiochem indicate that Nonidet P40 is an 
octylphenolpoly(ethylene glycol) ether.  There is no MErck index entry 
for Nonidet nor for the structure given by Boehringer for it. The 
difference between Nonidet P40 and Triton-X 100 probably is not structural, 
but rather company of  manufacturer. In the past there may have been small 
differences in average chain length (both are supposted to be N=9 to 10) 
and purity. I know some labs have gone to extreme measures to push thier 
belief that Nonidet P40 is not the same as Triton X100, but this view 
is not true (they are identical within the purity specs of 
these rather industrial-grade reagents). Nonidet P40 is often much more 
(10-times or more) expensive than Triton X-100, and for that reason it may 
have had a certain amount of appeal to pretense. The least expensive form 
of Nonidet P-40 I found was from CalBiochem, though it was still 2X more 
than Triton X-100.

Also, Nonidet P40 should not be referred to as NP 40 (as done by 
CalBiochem and some authors) since NP-40 is a Tergitol type detergent with 
a nonylphenol headgroup an average of 40 ethylene glycol groups. It is a 
solid at room temp.

An interesting aside is the fact that Triton X-100 is also a spermatocide, 
as is its close anonlog, nonoxynol-9. Of course, research grade chemicals 
are not approved for use on humans.

In  my experience, substituting TX-100 for Nonidet P40 in several published 
procedures had no effect on the experimental outcomes.

Curt Ashendel
Purdue University
West Lafayette, IN
ashendel at

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