Kindly analyse and please tell me, do the lcms match for the peptide Cys,His,Cys?
I want to know how to read this? Kindly summarize.
Thank you
Hi,
My first response would be: 'No'.
The precursor mass of peptide CHC 1+ would be m/z 362.09.
It seems however you've acquired a spectrum in negative ion mode? That is not typically done for peptides: do you have a specific reason not to look at positive ion mode data?
You'll need MS/MS data in order to confirm the amino acid sequence of a peptide: the resulting fragment ion ladder will help you with that. Although for such a small 'symmetric' peptide, the amount of information coming from a fragmentation spectrum will be limited.
Hope this helps!
Dear Eef,
You can use some software to compare this spectrum with peptide Cys,His,Cys spectrum.
Is this an LC/MS or an MS/MS scan? If MS/MS you convert this data into a peak list, you can use ProteinProspector [Protein Prospector, UCSF Mass Spectrometry Facility, Regents of the University of Californa, http://prospector.ucsf.edu/cgi-bin/msform.cgi?form=msproduct (2008)]. to match the fragments. If you want to understand how fragmentation works you might want to read the Seminal review by Klaus Biemann [ Biemann, K., “Sequencing of peptides by tandem mass spectrometry and high-energy collision-induced dissociation,” Meth. Enzymol., 193:455-479 (1990). ] or [ Papayannopoulos, I.A., “The interpretation of collision-induced dissociation tandem mass spectra of peptides,” Mass Spectrom. Rev., 14:49-73 (1995). ]
If this is an LC/MS scan, then you only need to know the parent mass of the peptide. The peptide 'flys' as a monoisotopic mass (Mo) + H+ ion in positive ion mode or as an [Mo - H+] mass in negative ion mode. However, it is possible that you might get a 2+ ion or a salt adduct (, Na+, K+ or NH4+). If your C residues are capped, then you need to add the mass of the capping agents. If not, then you might be getting some disulfides or oxidized C residues, both of which will shift the masses accordingly.
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