If you have a very pure protein sample, you'll want to use an ESI-ion trap for analyzing proteins of that size. It should be possible to get an exact mass (i.e. within a single Da). It's possible, but very rare, to get exact masses of proteins up to 100 kDa using ESI-ion trap instruments.
If your sample is not highly purified, you'll need to use some type of TOF instrument. MALDI-TOF should work. With a TOF instrument, you shouldn't expect to be able to distinguish between point mutants of a protein, but you'll be able to get information about larger changes. For instance, you'll be able to determine if you completely cleaved a his-tag off a construct. Our lab is spoiled because we have access to the HHMI Mass Spec facility, but I'd imagine that there are many facilities that can get accurate masses on 40 kDa proteins. -Joel ================================================= Joel M. Guenther PhD Candidate, Department of Chemistry Kuriyan Laboratory http://jkweb.berkeley.edu/ University of California, Berkeley 176 Stanley Hall, QB3 Berkeley, CA 94720-3220 tel: (510) 643 0166 fax: (510) 643 2352 ================================================= On 9/5/07, Jacob Keller <[EMAIL PROTECTED]> wrote: > > I second Dr. Loll's question, and would like to be CC'd in whatever MS > tips, including > service-providers, are sent. I have been having a bit of a debacle with a > certain MS service provider. > > Jacob Keller > > ==============Original message text=============== > On Wed, 05 Sep 2007 11:41:52 am CDT Patrick Loll wrote: > > I wonder if anyone would care to share experiences/ideas/biases that > relate to the use of mass spectrometry to verify the identity of > protein constructs used for crystallization. Our experience with > different MS facilities has been checquered. > > Specifically: > > What's the current thinking on the best approach to get masses for > intact proteins of moderate size (say, 40 kD)? ESI-TOF? > What kind of resolution should one hope to obtain in such cases > (10E-04?) > > Any suggestions as to good facilities offering fee for service MS > characterization are welcome (but should be shared off line, I think; > continental US only). > > Thanks, > > Pat > ------------------------------------------------------------------------ > --------------- > Patrick J. Loll, Ph. D. (215) > 762-7706 > Associate Professor FAX: (215) > 762-4452 > Department of Biochemistry & Molecular Biology > Director, Biochemistry Graduate Program > Drexel University College of Medicine > Room 10-102 New College Building > 245 N. 15th St., Mailstop 497 > Philadelphia, PA 19102-1192 USA > > [EMAIL PROTECTED] > > ===========End of original message text=========== > > > > *********************************** > Jacob Keller > Northwestern University > 6541 N. Francisco #3 > Chicago IL 60645 > (847)491-2438 > [EMAIL PROTECTED] > *********************************** >
