multiple antigenic peptides - MALDI

Lorne Taylor ltaylor at
Wed Jun 8 10:23:26 EST 1994

In article <2t20v0$cl6 at>, altabios at (John E. Fox) writes:
> We synthesise custom multiple antigenic peptides, (octomeric peptides) according to 
> the method of James Tamm, Immunol Methods (1989) 124, 53-61.
> As part of our quality control checks, we have tried to analyse them on a MALDI mass 
> spec. using gentisic acid as the matrix. 
> We see no sensible spectrum at all for any of the peptides we have made. 
> These peptides have molecular wieghts roughly in the range of 10KDa to 18KDa, 
> so they are well within the working range of our machine, (a Kratos MALDI 3).
> We have tried them on another machine with exactly the same results.
> Has anyone  else tried to mass spec these compounds? Anyone with an idea of why
> we have failed to see their spectra?

	We also had trouble with this type of peptide (8K Tamm) but finally got reasonable 
spectra from a dilute solution of matrix with concentrated peptide and low laser power.
	Have you tried different matrices? Our preferences for peptides
of this size are (in order of preference) 
1) alpha cyano-4-hydroxy cinnamic acid 
2) 3,5-methoxy-4-hydroxy-cinnamic acid 
3) 2,5 dihydroxybenzoic acid. 
	The spec we have (VG TofSpec) has slightly different capabilities
vis-a-vis laser power and density than your MALDI III but I don't think these
differences are the deciding factor.

Hope this helps.


ltaylor at

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