Go to homepage
Go to homepage
Your Cart
US$0.00

Cyclic Peptide Synthesis Services

Cyclic peptide synthesis for research, screening and peptide optimization projects. JPT supports multiple cyclization strategies, including disulfide, head-to-tail and side-chain amide cyclization, with project-specific purification, modifications and analytical quality control.


Cyclic Peptide Synthesis


20+ years
peptide expertise
1,000,000+
peptides synthesized per year
20,000+
global customers
3,000 +
publications citing JPT's peptides

Custom Cyclic Peptide Synthesis for Your Research Project

Peptide cyclization constrains a peptide into a defined ring structure and can reduce conformational flexibility compared with the corresponding linear sequence. Depending on the sequence and cyclization strategy, this can support improved proteolytic stability, binding selectivity or presentation of a biologically relevant conformation

Individual Cyclic Peptides


Custom synthesis of single cyclic peptide sequences with project-specific cyclization, purity, modifications and analytical QC.


Focused Cyclic Peptide Libraries

Defined sets of related cyclic peptide variants around a lead sequence, motif or scaffold for screening, structure-activity studies and sequence optimization.


Complex Cyclic Peptide Projects

Support for challenging designs involving advanced cyclization strategies, additional modifications and demanding synthesis or purification requirements.



Cyclization Strategies We Support


Peptide Cyclization Strategies

The preferred cyclization route depends on the sequence, ring size, desired conformation, available functional groups and downstream application. JPT can evaluate the sequence and help select a practical synthesis and cyclization strategy.

Amide bond

Head-to-Tail Cyclization

Connects the N- and C-termini through an amide bond. Efficient synthesis requires careful selection of the cyclization site, reagents and conditions to favor intramolecular ring closure and limit side reactions.



Consider when: backbone cyclization is needed and both termini are available for ring closure.
Disulfide bridge

Cys-Cys Cyclization

Forms a disulfide bridge between cysteine residues. For sequences with multiple cysteines, regioselective bridge formation may require orthogonal protection or controlled folding strategies.




JPT experience: projects can include peptides with up to four disulfide bonds, subject to sequence feasibility.
Lactam bridge

Side-Chain Amide Cyclization

Creates a chemically stable amide bridge between suitable side-chain functional groups. This approach can constrain the peptide while leaving the N- and C-termini available for other modifications.


Consider when: a stable side-chain constraint or a lactam bridge is preferred.
Project-specific chemistry

Alternative Cyclization Approaches

Other routes can be evaluated depending on the design, including thioether formation and click-chemistry-based cyclization. Feasibility depends on sequence, functional groups and required downstream modifications.

Need a broader macrocycle design? See our dedicated macrocyclic peptide synthesis service.
For more complex architectures such as stapled, bicyclic or other macrocyclic peptide formats, visit Macrocyclic Peptide Synthesis.

Cyclic Peptide Project Specifications

A useful quote starts with the sequence, required cyclization, amount, purity and any additional modifications. If the optimal cyclization route is not yet defined, our peptide team can review the project requirements with you.

  • Sequence & ring design: Sequence, cyclization sites, ring size and any required free termini or side chains. 
  • Scale & number of peptides: Individual peptides, focused sets or multi-peptide screening projects. 
  • Purity & purification: Project-specific purity targets and purification options based on downstream use and feasibility. 
  • Modifications & labels: Compatible PTMs, non-natural residues, labels, linkers or other peptide modifications. 
  • Analytical QC: HPLC and mass spectrometry options for identity and purity assessment, with additional analysis available by project. 
  • Delivery format: Individual tubes, library formats or project-specific organization for downstream workflows.


Design & Feasibility Support for Peptide Cyclization

Cyclization Cyclization is not only a ring-closure step. Sequence behavior, steric accessibility, aggregation, ring size and protecting-group strategy can all influence synthesis and purification. Early feasibility review helps reduce avoidable side reactions and select a realistic route. 

  • Selection of suitable cyclization sites and chemistry 
  • Strategies to limit intermolecular dimerization during ring closure 
  • Regioselective disulfide formation for multi-cysteine sequences 
  • Protection/deprotection planning for selective cyclization 
  • Evaluation of compatible labels, PTMs and non-natural amino acids 

For a deeper scientific overview of cyclization approaches and sequence-design considerations, read Cyclic Peptide Synthesis Strategies & Design Considerations.

Applications of Custom Cyclic Peptides 

Cyclic peptides are widely used where conformational control or enhanced resistance to proteolysis is beneficial. The optimal design depends on the biological question and downstream assay. 

Drug Discovery: Lead identification, binding optimization and exploration of constrained peptide chemical space.

Screening & SAR: Defined cyclic peptide sets and sequence variants for screening and structure-activity relationship studies. 

Protein Interaction: Research Constrained peptide ligands for studying binding interfaces, motifs and protein-protein interactions. 

Epitope & Structural Mimicry: Presentation of loop-like or constrained motifs for binding and recognition studies.


Cyclic Peptide Synthesis FAQ

The preferred method depends on the sequence, ring size, functional groups, desired stability and downstream application. Head-to-tail cyclization is useful for backbone closure, disulfide bridges are common for cysteine-containing motifs, and side-chain amide cyclization can provide a chemically stable constraint. JPT can review the design before quotation.
Yes. For multi-cysteine sequences, regioselective disulfide formation may require orthogonal protection or controlled folding approaches. JPT has experience with peptides containing up to four disulfide bonds, subject to sequence and project feasibility.
Many peptide modifications can be combined with cyclization when they are compatible with the synthesis and ring-closure chemistry. Include all required labels, PTMs, non-natural residues or conjugation handles in your project request so feasibility can be reviewed together.
Yes. JPT can support focused cyclic peptide sets for screening and optimization projects, with project-specific scale, purity, modifications and delivery formats. For larger or dedicated library projects, explore JPT's Cyclic Peptide Library service.
Please provide the peptide sequence, required cyclization type or desired constraint, amount, purity, number of peptides, modifications or labels, and the intended application. If the cyclization method is not yet defined, share the design goal and JPT can review feasible options.
Cyclic peptide synthesis is the broader category and includes commonly used ring-closure strategies such as disulfide and amide cyclization. Macrocyclic projects can involve larger or more specialized constrained architectures, including stapled, bicyclic and other macrocycle designs. For these projects, see JPT's dedicated Macrocyclic Peptide Synthesis service.
Loading...

Plan Your Cyclic Peptide Synthesis Project

Share your sequence and project specifications with JPT. We can review the cyclization strategy, modifications, scale, purity and analytical requirements before quotation.

Check our list of products, click and go.

Get a quote