Through unique partnerships with long-standing radio-synthesis groups, Cambridge Research Biochemicals (CRB) can provide radioactively (‘hot’) labelled peptides with Tritium (3H), Carbon-14 (14C) and Iodine-125 (125I).
Tritium (3H) labelled Peptides
Pure specifically tritiated peptides can be made for use in receptor studies, metabolic studies and pharmacological investigation.
Tritium reduction by catalytic exchange is the simplest and most economic route for labelling peptides that do not contain Cysteine residues.
Analogues of the peptide containing one or more of Phe, Pro, Tyr, or Leu residues substituted with a double bond or halogen moiety are synthesised at CRB and sent to the radio-synthesis group where these precursor peptides are then reduced with Tritium to generate the desired tritium labelled peptide with a specific activity in the range of 10-100Ci/mmole.
Carbon-14 (14C) labelled Peptides
Carbon-14 should only be considered after Tritium for two reasons: Carbon-14 can only be incorporated in to peptides via an expensive Carbon-14 labelled amino acid or by addition to the N-terminus of the peptide (e.g. 14C-Acetic acid to form 14C-Acetyl-peptide) and secondly due to the thousand-fold reduction in specific activity.
Iodine-125 (125I) labelled Peptides and proteins
Iodine-125, with a half-life of 60 days, is a cost-effective choice for labelling of peptides and proteins, as the reaction is performed directly on the peptide or protein sample. CRB offers a fixed fee service for iodination (2 x 50 µCi [125I]) and HPLC purification. For peptides and proteins containing tyrosine residues, iodination is carried out with Na125I activated with chloramin-T, lactoperoxidase or iodogen. Alternatively, free amino functions of the protein can be labelled using 125I-Bolton-Hunter reagent (creating a pseudo tyrosine within the molecule).