protein mass spec problem

Cornelius Krasel krasel at wpxx02.toxi.uni-wuerzburg.de
Mon May 12 12:27:06 EST 1997


Andrew Wallace (a.wallace at see.signature.qub.ac.uk) wrote:
> John E. Fox wrote:
> > Electrospray Mass Spectrometry on a purified recombinant protein.
> > Why multiple peaks?
> 
> Could they be different salts of the protein, e.g. Tris, Na+, etc.?
> This is often observed with smaller peptides, for example.

Could this also happen with MALDI? We have a recombinant protein that
gave *only* a peak which is 59 m/z too large. This would correspond
nicely to acetate, and indeed the protein was lyophilized from a
10 mM ammonium acetate solution. DNA sequence of the expression
vector looks okay. N-terminal posttranslational modification can be
excluded because the protein is cleaved from GST with Thrombin after
purification. The protein also reacts with antibodies made against
a full-sized version (recombinant, from Sf9 cells).

Puzzled,

--Cornelius.

-- 
/* Cornelius Krasel, U Wuerzburg, Dept. of Pharmacology, Versbacher Str. 9 */
/* D-97078 Wuerzburg, Germany   email: phak004 at rzbox.uni-wuerzburg.de  SP3 */
/* "Science is the game we play with God to find out what His rules are."  */



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