The mass you are calculating for bovine insulin b-chain is correct for
the native form, but what you are getting from sigma is Oxidized, so add
the mass of 6 oxygens and you get a mass (monoisotopic) of 3493.64
(M+H+ = 3494.65)
The mass (average) of cytochrome C that I get from SwisProt is 11701.6
with no modifications
add the N-terminal acetylation and the Heme (1 heme is covalently bound
to residues 14 & 17) and you get 12360.1 (M+H+ = 12361.1)
Hope this helps
Rick
Rick Edmondson
Senior Research Scientist
Rhone-Poulenc Rorer
Collegeville, PA 19426
phone: 610-454-3901
e-mail: rick.edmondson@rp-rorer.com
>----------
>From: Brett Phinney[SMTP:phinney@bchserver.bch.ncsu.edu]
>Sent: Friday, July 31, 1998 12:42 PM
>To: Recipients of ABRF List
>Subject: Mass of protein and peptide standards
>
>To all of the mass spec. experts,
>
>I have a question regarding the correct mass of several proteins and
>peptides that I have been using for calibration standards.
>
>One of the standards I have been using is Bovine Insulin oxidized beta
>chain. Sigma lists the mass as 3495.9 Bruker's calibration list also lists
>the monoisotopic mass as 3494.65. But when I pull the amino acid sequence
>from swiss-prot and Do the calculations on both Rockefellers web site and
>EMBL's web site, I get a monoisotopic mass of 3397.674. What could account
>for this mass difference? Am I doing something wrong?
>
>The other standard is Horse heart cytochrome C. Sigma lists the mass as
>12384, Bruker lists the average mass as 12361.088 and I get an average
>calculated mass of 12374.02 including 1 Fe atom and 1 heme group with a mass
>of 616.6. Additionally, when I buy my standards from Sigma, for example,
>What modifications are on the cytochrome C. Swis-prot says cytochrome C has
>the following modifications
>
>Post translational modification: 1 ACETYLATION
>Binding site: 14 HEME (Covalent)
>Binding site: 17 HEME (Covalent)
>Binding site for metal ion: 18 IRON (Heme axial ligand)
>Binding site for metal ion: 80 IRON (Heme axial ligand)
>
>But the average mass with all of these modifications (calculated from
>Rockefeller's web site (www.proteimetrics.com)is 13088.50.
>
>Which mass is correct? and what am I actually getting from sigma?
>
>Thanks a lot in advance for the help
>
>
>__________________________________
>Brett Phinney
>North Carolina State University
>Department of Biochemistry
>Ph# 919-515-5786, Fax 919-515-2047
>ICQ# = 12442943
>
>