I don't have any experience with the NBD group, but you can label the
N-terminus with FITC (or any other isothiocyanate), provided you first
attach a non-alpha amino acid (e.g., beta-alanine, 6-aminohexanoic acid,
etc.) linker to the N-terminus. Otherwise during the TFA cleavage step,
the labeled amino acid will undergo Edman degradation and you will lose the
label. Fluorescein is stable to the cleavage conditions. We have used
this strategy a number of times.
Richard Laursen
>For the labelling experts:
>A customer has requested a peptide in two versions labeled at the N-terminus
>with either fluorescein or NBD (7-nitrobenzo-2-oxa-1,3-diazole). I have two
>questions:
>
>1. In your experience, which is the best way to couple each fluorophore? The
>customer suggests the isothiacyanate (FITC and NBD-ITC, respectively). Is any
>of you familiar with those or can you suggest a better alternative?
>
>2. What kind of acid stability do these labels have? We can use either Boc
>(HF) or Fmoc (TFA) chemistry, but were successful with Boc chemistry before
>with the unlabelled peptide. Any advice on that?
>
>I am aware that similar questions have been asked before from the relatively
>few experts in the list. I am sorry for the reiteration. Thanks in advance for
>your advice. Best regards,
>
>
>
>
>
>
>
>
>
>I recall this type of questions being asked in the past, and
>
>
>David Andreu
>Universidad de Barcelona
>Depto. Quimica Organica
>Tel/Fax: 402 1260
>E-mail: andreu@admin.qo.ub.es
Richard A. Laursen
Department of Chemistry
Boston University
590 Commonwealth Ave.
Boston, MA 02215
(617) 353-2491 (office)
(617) 353-2485 (lab)
(617) 353-6466 (FAX)
laursen@bu.edu