Peptide Modification Services

Peptide Modification Services

Research-grade modified peptides — labeling, conjugation, and structural modifications, confirmed by HPLC and MS.

Peptide Modification Built for Your Research

SynPeptide adds modifications to peptides that change how they behave: a label to track them, a PEG chain to extend half-life, a cyclization to lock structure, or a carrier protein to raise antibodies. We handle N- and C-terminal modifications, fluorescent and biotin labeling, PEGylation, cyclization, phosphorylation, methylation, isotope labeling, and carrier conjugation. Every modified peptide is purified in-house and confirmed by HPLC and mass spectrometry, with the modification site documented. Since 2013 we have made modified peptides for researchers in more than 100 countries.

Over 10 Modification Types

Acetylation, amidation, labeling, PEGylation, cyclization, conjugation, and more, all under one roof.


Site-Specific Labeling

Labels and groups go exactly where you specify, with positional specificity confirmed.


MS-Confirmed Every Time

Every modified peptide is checked by HPLC and mass spectrometry before it ships.


Backed by 50+ Patents

Built on more than 50 granted patents and over 15,600 academic citations since 2013.


Specifications

ModificationExamplesTypical Use
MODIFICATIONS OFFERED
Terminal ModificationsN-terminal acetylation / acylation, C-terminal amidationBlock degradation, mimic native termini
Fluorescent & Dye LabelingFITC, FAM, TAMRA, Cy3, Cy5, rhodamine, FRET pairsImaging, uptake, binding, protease assays
BiotinylationN-/C-terminal or side-chain, optional spacer armStreptavidin pull-down, ELISA, detection
PEGylationLinear or branched mPEG, defined molecular weightLonger half-life, better solubility
CyclizationDisulfide, head-to-tail, side-chain, thioetherConformational constraint, stability
PhosphorylationPhosphoserine, phosphothreonine, phosphotyrosineSignaling, kinase, antibody work
MethylationN-methyl backbone; mono-, di-, tri-methyl Lys or ArgProtease resistance, epigenetics
Carrier ConjugationKLH, BSA, OVA; multiple antigen peptide (MAP)Immunogens for antibody production
Stable Isotope LabelingCarbon-13, nitrogen-15, deuterium (AQUA-grade)MS quantitation, NMR
QUALITY CONTROL
QC DocumentationCOA · HPLC · MSIncluded
Modification ConfirmationIdentity and modification site verified by MSStandard
DELIVERY
Delivery FormatLyophilized powder (default)Lyophilized
Counterion / Salt FormTFA salt by default; acetate or HCl exchange availableOn request
Storage & StabilityStore lyophilized at −20°C, away from light and moistureBeyond 2 years (sequence dependent)
* Feasibility and timeline depend on the sequence, the modification, and the position. Contact us for a project-specific quote.


Modifications We Offer

From terminal capping and labeling to PEGylation, cyclization, and carrier conjugation, we cover the modifications most research and drug-development projects need.

Terminal Modifications

N-terminal acetylation and C-terminal amidation cap the ends, block exopeptidase degradation, and better mimic the native protein.


Fluorescent & Dye Labeling

FITC, FAM, TAMRA, Cy3, Cy5, and FRET pairs for imaging, cellular uptake, binding, and protease assays, placed at the site you choose.


Biotinylation

Biotin at the N-terminus, C-terminus, or a side chain, with an optional spacer arm, for streptavidin pull-down, ELISA, and detection.


PEGylation

Linear or branched mPEG of defined molecular weight to extend half-life and improve solubility for peptide therapeutics.


Cyclization & Disulfide Bridging

Disulfide, head-to-tail, side-chain, and thioether cyclization to constrain conformation and resist proteases.


Phosphorylation & Methylation

Phosphoserine, phosphothreonine, and phosphotyrosine, plus mono-, di-, and tri-methylation, for signaling, kinase, and epigenetics work.


Carrier-Protein Conjugation

Conjugation to KLH, BSA, or OVA, and MAP cores, to turn short peptides into immunogens for antibody production.


Stable Isotope Labeling

Carbon-13, nitrogen-15, and deuterium labeling for absolute protein quantitation by mass spectrometry and for NMR.




Site-Specific Modification

The hard part of modification is putting the group in the right place and nowhere else. We control whether a label sits at the N-terminus, C-terminus, or a specific side chain, and whether one residue or several carry it. For a peptide with multiple lysines or cysteines, we use orthogonal protecting groups so the modification lands on the intended residue.

· N-terminal, C-terminal, or side-chain placement
· Single-site or multi-site labeling
· Orthogonal protection for selective modification
· Positional specificity confirmed by MS



Labeling for Detection and Imaging

Labeled peptides are the workhorses of detection. We attach fluorophores such as FITC, FAM, TAMRA, and the Cy dyes, build FRET donor and quencher pairs for protease assays, and add biotin for streptavidin capture. Where a dye would quench against another label, we suggest a spacer to keep the signal clean.

· Fluorescent dyes: FITC, FAM, TAMRA, Cy3, Cy5, rhodamine
· FRET donor and quencher pairs
· Biotin with optional spacer arms
· Dual labeling on request



Modifications for Peptide Therapeutics

Modifications are how a peptide lead becomes a drug candidate. PEGylation extends circulation time and cuts renal clearance, terminal capping and cyclization slow proteolysis, and defined salt forms improve handling. We work from research quantities up to large-scale production for a development program.

· Linear and branched PEG of defined MW
· Cyclization and terminal capping for stability
· Salt-form and counterion exchange
· Research to development scale



Modification Confirmation and QC

A modification only counts if you can prove it is there and in the right spot. Every modified peptide is checked by HPLC for purity and by mass spectrometry for identity and modification site. For labeled peptides we report labeling efficiency, and for CDMO and large-scale projects we add extended documentation such as batch records and method development.

· HPLC purity on every batch
· MS identity and modification-site confirmation
· Labeling-efficiency reporting
· COA included as standard

About SynPeptide

Founded in 2013 in Nanjing, China. 150+ team members, 50+ patents, 15,600+ citations. Serving 100,000+ researchers in 100+ countries.

About Us Facility Downloads

FAQs

What information do you need to modify my peptide?

To start, send the peptide sequence, the modification you want, and where it should go (N-terminus, C-terminus, or a named residue). For labels, tell us the fluorophore or tag; for PEGylation, the PEG size; for conjugation, the carrier protein. The intended application helps us flag any conflict between the modification and the sequence.

Can you put a modification at a specific position?

Yes. Site-specific modification is the core of this work. We place a label or group at the N-terminus, C-terminus, or a chosen side chain, and use orthogonal protecting groups when a sequence has several reactive residues. The position is confirmed by mass spectrometry.

Can a peptide carry more than one modification?

Yes. We routinely combine modifications, such as a fluorophore on one end and biotin on the other, or a phosphorylation plus a label. Where two groups might interfere, we adjust the placement or add a spacer, and confirm each one by MS.

Which fluorescent label or dye should I choose?

It depends on your instrument and assay. FITC and FAM are common green dyes for general detection. TAMRA and the Cy dyes suit multiplexing and red channels. For protease assays, a FRET donor and quencher pair works best. Tell us your filter set and we will match the dye.

How do you confirm the modification is present and correct?

Every modified peptide is purified by HPLC and analyzed by mass spectrometry, which confirms both identity and the modification site. For labeled peptides we also report labeling efficiency. A COA, HPLC chromatogram, and MS report come with every order.

Can you modify a peptide I already have, or do you synthesize it too?

Most modifications are built in during synthesis, which gives the cleanest result and exact site control. We synthesize the peptide and add the modification in one workflow. If you need a peptide you already hold to be conjugated or labeled, contact us with the details and we will check feasibility.

Which modifications help extend a peptide's half-life or stability?

PEGylation extends circulation time and reduces renal clearance, which is why it is common for peptide therapeutics. Terminal capping (N-terminal acetylation, C-terminal amidation) and cyclization slow enzymatic degradation. The right combination depends on the target, the route, and how long you need the peptide to last.

Do you conjugate peptides to carrier proteins for antibody production?

Yes. We conjugate peptides to KLH, BSA, or OVA, and build multiple antigen peptide (MAP) cores. Carrier conjugation turns a short peptide into an immunogen strong enough to raise antibodies. KLH is the usual first choice for immunization.

Understanding Peptide Modification

Peptide modification is the deliberate addition or alteration of chemical groups on a synthetic peptide to change how it behaves. A plain sequence of amino acids is often degraded quickly, hard to detect, or poorly suited to its job. Adding a label, a polymer, a charge change, or a structural bridge fixes that. Modifications range from simple terminal capping to fluorescent labels, biotin tags, PEG chains, phosphorylation, and conjugation to carrier proteins.

Why Modify a Peptide

Each modification solves a specific problem. Labels make a peptide visible in imaging or pull-down assays. Terminal capping and cyclization protect it from enzymes so it lasts longer in cells or serum. PEGylation extends half-life for therapeutic use. Carrier conjugation makes a short peptide immunogenic so it can raise antibodies. Phosphorylation and methylation reproduce the post-translational marks that drive signaling and gene regulation.

Where the Modification Goes

Placement matters as much as the group itself. N-terminal modifications, such as acetylation or acylation, sit at the free amino end and often block aminopeptidases. C-terminal amidation replaces the terminal carboxyl with an amide, which mimics many natural peptides and slows carboxypeptidase cleavage. Side-chain modifications target a specific residue, for example a phosphate on serine or a dye on a lysine. When a sequence has several reactive residues, orthogonal protecting groups keep the modification on the one you want.

Common Modifications and What They Do

A short reference for the modifications researchers ask for most:

  • Acetylation and amidation — cap the termini, block degradation, mimic native peptides.
  • Fluorescent labeling — FITC, FAM, TAMRA, and Cy dyes for imaging, uptake, and binding studies.
  • Biotinylation — a biotin tag for streptavidin capture, ELISA, and detection.
  • PEGylation — a PEG chain to extend half-life and improve solubility.
  • Cyclization — disulfide or backbone bridges to lock structure and resist proteases.
  • Phosphorylation and methylation — post-translational marks for signaling and epigenetics work.
  • Carbamidomethylation — a carbamidomethyl group on cysteine, the standard way to protect thiols in proteomics sample prep before mass spectrometry.
  • Carrier conjugation — KLH, BSA, or OVA to turn a peptide into an immunogen.

How to Choose and Order

Start from the experiment. Decide what the modification needs to achieve, then pick the group and the position. If you are unsure, send the sequence and the application and we will recommend an approach. Most modifications are added during custom peptide synthesis, so the peptide and its modification arrive as one finished, documented product.

All modified peptides are supplied for research, analytical, and pharmaceutical development use.

Explore More Services

Custom Peptide Synthesis

Custom Peptide Synthesis

Explore

Peptide Modification Services

Peptide Modification Services

Explore

Large-Scale Peptide Synthesis

Large-Scale Peptide Synthesis

Explore

Peptide Drug Development (CDMO)

Peptide Drug Development (CDMO)

Explore

Online Consultation Email: dora@synpeptide.com Tel: +86 135 0517 2290 WhatsApp: +86 135 0517 2290