Fmoc-Phe-Gly-PAB is a protected L-Phe-Gly-p-aminobenzyl alcohol (PAB) fragment that combines a defined dipeptide sequence with a para-aminobenzyl spacer. The N-terminal Fmoc group supports controlled peptide extension, while the PAB benzylic alcohol provides a functional handle for downstream linker or payload derivatization.

This architecture is relevant to research on peptide-cleavable linkers, self-immolative spacer systems and antibody-drug or peptide-drug conjugate construction. PAB/PABC motifs are widely used as spacer elements that can relay an upstream enzymatic cleavage event into downstream payload release; however, cleavage behavior is determined by the complete linker architecture and should not be inferred from the protected building block alone.

Product Information

Why Combine a Peptide Trigger with a PAB Spacer?

Para-aminobenzyl spacer chemistry is well established in cleavable conjugate design. In many ADC linker systems, a protease-sensitive peptide trigger is positioned upstream of a PAB/PABC-type self-immolative spacer. Enzymatic cleavage exposes the spacer and can initiate a spontaneous fragmentation sequence that releases an attached payload.

Fmoc-Phe-Gly-PAB provides a preassembled protected fragment for exploring related modular linker architectures. The exact protease sensitivity of a Phe-Gly-PAB construct should be established experimentally because enzyme recognition depends on the peptide sequence, neighboring groups, attachment chemistry and final conjugate.

PAB vs PABC Terminology

PAB refers to the p-aminobenzyl alcohol scaffold. PABC commonly refers to a p-aminobenzyl carbamate form after the benzylic hydroxyl has been converted into a carbamate linkage to a payload. These terms are related but should not be treated as chemically identical.

For procurement, confirming whether a product is the free PAB alcohol, a PABC carbamate, or another derivatized spacer is important because the terminal functionality determines the next synthetic step.

Application Scope

Potential uses include peptide-linker synthesis, ADC/PDC linker research, self-immolative spacer development, preparation of protease-responsive conjugate intermediates and synthesis of linker-payload precursors.

The protected building block itself is not a direct in vitro or in vivo assay reagent. Final constructs may be evaluated in protease-cleavage assays, plasma-stability studies, lysosomal processing experiments, cell-based payload-release assays or in vivo studies after complete conjugation and analytical characterization.

Purchasing and QC Considerations

Because no reliable public CAS assignment was confirmed for this exact protected fragment, procurement should use Catalog No. AS4069 together with the structural description, molecular formula, molecular weight and lot-specific COA. Confirm the L-Phe-Gly sequence orientation, Fmoc protection and free PAB benzylic alcohol before using the material in linker synthesis.

Product Documents

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

MSDS_Fmoc-Phe-Gly-PAB_AS4069

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 is Fmoc-Phe-Gly-PAB used for?

It is used as a protected peptide-linker fragment for research on conjugation, protease-cleavable linkers and PAB/PABC-type self-immolative spacer systems.

Is PAB the same as PABC?

No. PAB is the p-aminobenzyl alcohol scaffold; PABC generally refers to the corresponding carbamate linkage used to connect a payload.

Does Fmoc-Phe-Gly-PAB guarantee cathepsin cleavage?

No. Protease cleavage is a property of the complete linker and biological context. It should be confirmed experimentally in the final construct.

Related Technical Resources

Explore additional Specialty Peptide Building Blocks for protected fragments, peptide linkers and conjugation intermediates.

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