Fmoc-Gly-Gly-Phe-Gly-OH, commonly abbreviated Fmoc-GGFG-OH, is an Fmoc-protected tetrapeptide linker building block containing the Gly-Gly-L-Phe-Gly (GGFG) sequence. The GGFG motif is widely used in protease-cleavable linker architectures for antibody-drug conjugate (ADC) and bioconjugation research.

The fragment combines three small glycine residues with a single L-phenylalanine that introduces an aromatic, protease-recognition-relevant side chain. It provides an Fmoc-protected N-terminal amine and a free C-terminal carboxylic acid for stepwise construction of more complex linker-payload systems.

Product Information

Why the GGFG Motif Is Used in ADC Linker Research

GGFG is a peptide-based linker motif used in ADC architectures designed for intracellular protease processing. The glycine-rich segment provides conformational flexibility, while phenylalanine contributes a hydrophobic side chain that changes the sequence from a purely oligoglycine spacer into a defined protease-cleavable motif.

Fmoc-GGFG-OH is an upstream linker fragment, not a complete drug-linker or ADC. Actual plasma stability, lysosomal cleavage and payload release depend on the groups attached to both ends and must be measured on the final construct.

Two Functional Handles for Linker Assembly

The N-terminal Fmoc group can be removed under standard basic Fmoc-deprotection conditions to reveal an amine for further conjugation. The free C-terminal carboxyl group can be activated for coupling to amine-containing spacers, payload precursors or other linker components.

This bidirectional synthetic logic makes Fmoc-GGFG-OH useful for modular ADC/PDC linker assembly and for preparing test constructs used in protease-cleavage and stability studies.

Application Scope and Assay Relevance

Applications include antibody-drug conjugate linker synthesis, peptide-drug conjugate development, protease-cleavable linker research, payload-linker intermediate preparation and bioconjugation chemistry.

Downstream experiments may include lysosomal or protease cleavage assays, plasma-stability studies, payload-release characterization, cell-based cytotoxicity assays and in vivo evaluation of completed conjugates. Those assays apply to the final linker/conjugate, not to the protected Fmoc-GGFG-OH building block itself.

Fmoc-GGFG-OH vs Triglycine Linkers

Fmoc-Gly-Gly-Gly-OH is a shorter all-glycine linker, whereas Fmoc-GGFG-OH introduces L-Phe and a defined GGFG cleavage motif. They should not be treated as interchangeable simply because both are used in conjugation workflows.

Purchasing and QC Considerations

Confirm the exact GGFG sequence, L-Phe stereochemistry, Fmoc protection, CAS number and terminal carboxyl group. In linker chemistry, a sequence error or D/L substitution at Phe can alter protease processing, so lot-specific identity data are especially important.

Product Documents

A Material Safety Data Sheet (MSDS) is available for this product to support laboratory handling, storage and safety assessment.

MSDS_Fmoc-Gly-Gly-Phe-Gly-OH_AS4065

Certificates of Analysis (COAs) are batch-specific. Please contact us to request the COA for your product, and we will provide it by email.

Frequently Asked Questions

What does GGFG stand for?

GGFG is Gly-Gly-Phe-Gly. In this product, the phenylalanine residue is L-Phe.

Is Fmoc-GGFG-OH an ADC?

No. It is a protected peptide linker building block used to construct ADC or other bioconjugate linker systems.

Can GGFG-containing linkers be tested for protease cleavage?

Yes. Completed GGFG-containing linker or conjugate constructs can be evaluated in protease or lysosomal cleavage assays; cleavage depends on the full molecular context.

Related Technical Resources

Explore additional Specialty Peptide Building Blocks for protected fragments, linker motifs and peptide-synthesis intermediates.

For sequence-specific synthesis, protected-fragment assembly and modified peptide projects, see our Chemical Peptide Synthesis service.

Research Use Only.