Bye,
Alex
SCM11@leicester.ac.uk wrote:
> To all peptide synthesis experts,
>
> We have synthesised a peptide with the following sequence -
> N-terminus C-Y-A-S-I-N-F-Q-K-Q-P-E-D-R-Q C-terminus.(Calculated
> Mw=1827.01Da)
> The synthesis was performed on ABI-431A synthesiser, 0.25mM scale with FastMoc
> solid phase chemistry.
> Reverse phase-HPLC analysis of the peptide showed a double peak, the second
> peak forming a shoulder to the major peak.
> MALDI-TOF mass analysis of the two peaks showed the major HPLC peak contained a
> peptide of mass m/z =1828.12. The second HPLC peak has the mass m/z = 1809.96
> (with some contaminating m/z=1828.64 peak). The two peaks have a mass
> difference of approximately 18 daltons.
>
> Initially we assumed that a proportion of the serine at residue 4 may have been
> converted to dehydroalanine and have tried to confirm this by Edman sequencing.
> However the ratios of serine to dehydroalanine and serine to tyrosine in cycle
> 2 and alanine in cycle 3 on sequencing of the two peptide species appear
> similar.
>
> Does any one have an explanation how this loss of 18 daltons has occurred?
>
> Thanks in advance
>
> From: Sharad Mistry,
> PNACL,
> University of Leicester,
> Lancaster Road,
> Leicester, LE1 9HN, U.K.
> Tel: +44 (0)116 252 5531
> Fax: +44 (0)116 252 5616
> Email: scm11@leicester.ac.uk
-- ====================================================================== Dr. Alessandro Tossi Antiinfective peptides group Dept. of Biochemistry, Biophysics and Macromolecular Chemistry University of Trieste Phone -- 39 40 6763673; Fax -- 39 40 6763691 email: tossi@bbcm.univ.trieste.it http://www.bbcm.univ.trieste.it/~tossi =====================================================================