Has anyone used fluorescein-5-maleimide to label a peptide?

Roger Murphy murphy_r at licre.ludwig.edu.au
Wed Apr 1 01:16:09 EST 1998

Kate, what pH is the buffer you've using?  The sulphydryl group is really only 
reactive above pH 8, and it's "activity" drops by a factor of approx. 10 for 
every pH unit lower.  I'm sure you've checked this (by mass spec.), but your 
peptide hasn't dimerised via S-S bond has it?


In article <k.michie-ya023480003103981745590001 at>, 
k.michie at biochem.usyd.edu.au wrote:
>I am trying to label a small peptide with fluorescein-5-maleimide (F5M)
>with little success. The peptide has only one Cysteine. I have tried to
>incubate the peptide and F5M in a buffer (as suggested by the chemical
>company support notes) for 2 hours, however, analysis by HPLC shows little
>to no yield. Has anyone else had any success? What am I doing wrong?! Any
>Katharine Michie
>Department of Biochemistry
>University of Sydney

Roger Murphy, Ph.D.
Biological Production Facility
Ludwig Institute for Cancer Research
Austin & Repatriation Medical Centre
Studley Road,
Heidelberg,  Vic. 3084

Tel  61-3-94965463
Fax  61-3-94965436
Email murphy_r at licre.ludwig.edu.au

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