Modified and labeled peptides are sequence-defined peptides carrying engineering additions — post-translational mimetics, fluorophores, biotin and click handles, PEG or lipid chains, isotopic labels, and backbone or closure modifications — turning any standard peptide into a probe, drug lead, or self-assembling module.
5–80 aa + N/C/side-chain labeling · backbone edit
Biotin · Fluor · PTM · PEG · Lipid · Isotope
HPLC + MS · site-report · mg → kg
What Are Modified & Labeled Peptides
Any peptide extended beyond the 20 natural amino acids: PTM mimetics (phosphorylation, sulfation, glycosylation, lipidation, hydroxylation, acetylation, methylation), detection labels (biotin, fluorophores, click handles), affinity tags (His6, FLAG, HA, Myc), isotopic labels, and backbone / closure chemistry (D-amino acids, β-amino acids, cyclization, hydrocarbon staples).
Position-Specific Engineering
Each modification is installed at a defined residue by orthogonal protecting groups: Lys(Alloc)/Lys(Dde) for selective deprotection, Cys/Pen for thioether, azide-Lys / propargyl-Gly for click handles, Fmoc-pSer / Fmoc-pTyr for native phosphate, Fmoc-GlcNAc-Ser / Fmoc-Man-Asn for N-/O-glycans, and Dde/Dod for late-stage bifurcated assembly.
Application Channels
Used as affinity-capture baits (biotin–streptavidin), fluorescent reporters (FITC / Alexa / Cy), NMR/MRI/γ-imaging isotopes, half-life extenders (PEG, lipid), oral peptides (semaglutide-style backbone / lipidation), and self-assembling scaffolds (stapled / cyclic / branched).
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![Biotin-Crosstide CAS 923949-90-0]()
Biotin-Crosstide CAS 923949-90-0CAS: 923949-90-0Sequence: {Biotin}-GRPRTSSFAEGWe also provide specifications from crude to 99% purity, please contact us for details!Related documentsCOA/MS/HPLC ReportPeptide Dissolution and Storage -
![Pam3CSK4-Biotin CAS 1429504-10-8]()
Pam3CSK4-Biotin CAS 1429504-10-8CAS: 1429504-10-8Sequence: {(Pam3)Cys}-SKKK-{Lys(Aca-Aca-Biotin)}We also provide specifications from crude to 99% purity, please contact us for details!Related documentsCOA/MS/HPLC ReportPeptide -
![5-FAM-LL-37 (scrambled) CAS 2022972-73-0]()
5-FAM-LL-37 (scrambled) CAS 2022972-73-0CAS Number: 2022972-73-0Sequence: {5-FAM}-GLKLRFEFSKIKGEFLKTPEVRFRDIKLKDNRISVQRWe also provide specifications from crude to 99% purity, please contact us for details!Related documentsCOA/MS/HPLC -
![5-FAM-Woodtide CAS 1566528-51-5]()
5-FAM-Woodtide CAS 1566528-51-5CAS Number: 1566528-51-5Sequence: 5-FAM-KKISGRLSPIMTEQ-NH2We also provide specifications from crude to 99% purity, please contact us for details!Related documentsCOA/MS/HPLC ReportPeptide Dissolution -
![Dnp-PYAYWMR CAS 135662-06-5]()
Dnp-PYAYWMR CAS 135662-06-5CAS Number: 135662-06-5Sequence: {DNP}-PYAYWMRWe also provide specifications from crude to 99% purity, please contact us for details!Related documentsCOA/MS/HPLC ReportPeptide Dissolution and Storage
Modified & Labeled Peptides — Frequently Asked Questions
Which biotinylation chemistry should I pick?
NHS-ester (Biotin-X-NHS) modifies Lys ε-amino groups under pH 7–8; maleimide (Biotin-Mal / Biotin-PEGn-Mal) targets reduced Cys thiols with high specificity. Click handles (azido-Lys + DBCO-Biotin, or propargyl-Gly + azido-Biotin) work on peptide-resin via CuAAC or strain-promoted SPAAC. Enzymatic biotinylation at AviTag uses BirA for site-specific single biotin.
How do I choose a fluorophore — and which FRET pair?
UV-blue: EDANS, FAM, Alexa 488. Vis-green: FITC, Cy3, Alexa 546. Vis-red: TAMRA, Cy3.5. NIR: Cy5, Cy5.5, Alexa 647 (low autofluorescence, tissue-depth imaging). Standard FRET pairs: EDANS–DABCYL, FAM–TAMRA, Alexa 488–QSY 7 / QSY 9, Cy3–Cy5; spacing is tuned with Ahx / Mini-PEG / β-Ala to give >50% energy transfer.
Which PTM mimetics are available beyond phosphorylation?
Sulfation on Tyr (Fmoc-Tyr(SO3Bn)-OH, post-cleavage deprotection), N-/O-glycosylation (Fmoc-Ser/Thr-GlcNAc, Fmoc-Asn-Man / GalNAc), C-/N-myristoylation & S-palmitoylation (fatty-acid cassettes), Lys acetylation (Fmoc-Lys(Ac)-OH), Arg/Lys methylation (mono-, di-, symmetric / asymmetric di-Me), citrullination (Fmoc-Cit), and proline hydroxylation (Fmoc-Hyp).
How do I choose a PEGylation strategy?
mPEG-NHS ester modifies Lys ε-amino or N-terminus; mPEG-maleimide targets reduced Cys for site-specific mono-PEG; mPEG-propionaldehyde / mPEG-aldehyde performs N-terminal reductive amination. Linear vs branched (Y-shape / fork-shape) and size 0.5–40 kDa are tuned to solubility / half-life / receptor potency; PEG-purity, free-PEG and conjugates are resolved by RP-HPLC + GPC + MALDI-TOF.
Which backbone / unnatural residues should I use for stability?
D-amino acid substitution is the first line for protease resistance. α-Aminoisobutyric acid (Aib), β2/β3-amino acids, and cyclopentane / cyclohexane-constrained analogs lock secondary structure. Nle / Orn / Dab / homo-amino acids extend spacing or add side-chain length. Semaglutide-style oral peptides combine Aib, Lys26-AEEA2 mini-PEG, and C16 fatty diacid in a single chain.
Which orthogonal ligation chemistries do you provide?
Cu-free SPAAC (azido-Lys / DBCO-Lys / BCN-Lys) and CuAAC (propargyl-Gly + azide) for click labeling. Native chemical ligation (NCL) on Cys-thioester pairs for large or difficult sequences. Sortase A —LPETG— ligation, SpyTag-SpyCatcher isopeptide bond, and BirA / AviTag enzymatic biotinylation for site-specific >95% conversion; HaloTag / SNAP-tag / CLIP-tag for chemical coupling.
Shanghai Sonyt Biotechnology Co., Ltd. is one of the most reliable modified and labeled peptides manufacturers and suppliers in China. With abundant experience, we warmly welcome you to wholesale custom made modified and labeled peptides from our factory. If you have any enquiry about cooperation, please feel free to email us.
