SDS debate

Nick Theodorakis nicholas_theodorakis at
Thu Aug 9 19:23:52 EST 2001

In <Pine.SGI.4.33.0108091040010.4361379-100000 at>, Michael
Witty wrote:
>Dear All,
>        there is a debate in my lab about the extent to which SDS
>denatures protein.  I think that SDS sticks, but the gross shape of the
>protein is not altered very much (the protein still looks like a ball of
>wool).  My collegue thinks that the protein is dramatically unfolded and
>looks like a linear object, or a ball of wool unrolled.  What do we think?
>Regards, Mike.

From: _Biophysical Chemistry. Part II: Techniques for the Study of Biological
Structure and Function_  Cantor, CR and Schimmel, PR. WH Freeman & Co. (1980),
pp. 679-680.

"... SDS is an effective protein denaturant. It binds to all proteins
qualitatively the same, at about 1.4 g per gram of amino acid. There is one
negative charge on each SDS molecule. The resulting charge density due to all
the SDS in the SDS-protein complex more-or-less overwhelms variations in the
charges of different protein molecules. ... Charles Tanford and others have
studied the structure of SDS-protein complexes. Hydrodynamically, they appear to
be prolate ellipsoids or rods with a constant diameter of about 18 angstroms and
a length that is linear function of the molecule. ..."


Nick Theodorakis
nicholas_theodorakis at


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