Epitope Peptides

B-cell epitopes are recognized directly by soluble or membrane-bound antibodies and are typically 12–20 aa long (linear) or assembled from non-contiguous residues brought together by folding (conformational). T-cell epitopes are short peptides of 8–11 residues (MHC-I, recognized by CD8 T cells) or 13–25 residues (MHC-II, CD4) that must first bind inside the MHC groove before the TCR engages. The two classes require entirely different peptide lengths, controls and assay formats.

The protein sequence is fragmented into 15–20-mer peptides with a 3–5 residue overlap between neighbors, which keeps any linear epitope present in at least one peptide. Typical output is 60–300+ peptides for a 30–100 kDa target. N- and C-terminal cysteines are added when peptides are destined for SPOT membrane or maleimide-thiol array coupling.

Predicted MHC-I binders are identified computationally (NetMHCpan, MHCflurry, SYFPEITHI) by their allele-specific anchor residues (e.g. HLA-A*02:01 prefers position-2 L/V/I and C-term L/F/Y). Top 1–5% candidates are synthesized as 8–11-mer peptides, optionally biotinylated on a flexible linker at the N-terminus, and validated by in vitro refolding of recombinant MHC and by pMHC tetramer staining.

We deliver cyclized mimotopes by head-to-tail, side-chain-to-side-chain, or disulfide-bridge cyclization to lock in a turn structure; constrained scaffolds (e.g. grafting the contact loop onto a stable β-hairpin or thioredoxin); and peptide mimetics built from phage-display mimotope hits or from anti-idiotype antibody CDR outputs. Constraint choice is recorded on the CoA so each peptide can be reproduced exactly.

KLH is the standard carrier for raising polyclonal and most monoclonal antibodies, BSA / OVA / TT for ELISA coating and pre-absorption, and maleimide-activated carriers for site-specific Cys coupling. SMCC or SMPB is used to preserve epitope orientation; glutaraldehyde is avoided for short peptides because it crosslinks the epitope itself. Hapten density (typically 10–30 peptides / carrier) is reported in the CoA.

Yes — parallel SPOT synthesis on cellulose membranes (up to ~10–15-mers), CelluSpots / pepspot arrays on glass slides (up to ~2,000 peptides / array), and biotinylated peptide arrays on streptavidin-coated plates are all supported. Each spot is QC-confirmed by HPLC/MS of an analytical aliquot before array assembly, and arrays ship with a peptide–position map and on-array binding protocol.