Sylvie,
If, by a chance, your peptide(s) in question have Cys-OH residue at the
C-term than this +51amu peak represents likely a modification at Cys
resulting from substituting of the -SH moiety by piperidine (see reference
below). This "impurity" (not seen in C-term Cys-amides), depending on
peptide resin and peptide sequence, may occasionally represent a major
synthetic product. Due to an extra basic site in the sequence, the relative
peak intensity of this species in the positive mode of MALDI is much higher
than in negative mode. However, if you observe these +51 amu peaks in
samples w/o Cys-OH at C-term, the above explanation would not apply.
"3-(1-Piperidinyl)alanine Formation During the Preparation
of C-terminal Cysteine Peptides with the Fmoc/t-Bu Strategy."
Lukszo J., Patterson D., Albericio F., Kates S.A.,
Letters in Peptide Science 1996, 3, 157-166.
Jan Lukszo
At 03:16 PM 12/7/00 -0500, you wrote:
>Dear all,
>
>We got a MALDI DE-PRO recently and one of our applications is quality
>control of our synthetic peptide. Recently, we saw +51 adduct on some of
>our peptides. We looked at the delta mass web site and see nothing in
>this range. Does someone know what it could be?
>
>As always, we really appreciate your help!
>
>Sylvie
>
>Sylvie Bourassa Ph.D.
>Service Proteomique de l'Est du QuÈbec (SPEQ)
>Anciennement: Service de Sequence de Peptides de l'Est du Quebec (SSPEQ)
>CHUL Research Center Room 9700
>2705, Laurier blvd
>Ste-Foy, Quebec
>Canada G1V 4G2
>phone: 418-656-4141 ext 7088 /418-654-2267
>fax: 418-654-2159
>Email: sspeq@crchul.ulaval.ca
>
>http://www.crchul.ulaval.ca/crchul/fr/serv/sspeq.asp
>
>
>
>
Dr. Jan Lukszo
Peptide Analysis and Synthesis Unit
NIH/NIAID/OSD/SBS
Twinbrook II
12441 Parklawn Drive
Rockville, MD 20852
phone:(301)496-3786
fax:(301)480-2618
E-Mail: lukszo@ncisun1.ncifcrf.gov
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