Fmoc-Gly-Gly-Gly-Gly-OH, also known as Fmoc-Gly4-OH or Fmoc-tetraglycine, is a preassembled four-glycine peptide fragment with an Fmoc-protected N-terminus and free C-terminal carboxylic acid. It provides a defined Gly₄ unit for flexible peptide spacers, conjugation linkers and glycine-rich sequence assembly.

A preassembled tetraglycine fragment can reduce repetitive glycine coupling operations while preserving a chemically simple, side-chain-free spacer. This is useful when the final design requires a specific four-glycine distance rather than an undefined “flexible linker.”

Product Information

Why Use a Gly4 Spacer?

Four consecutive glycine residues produce a flexible peptide segment with minimal side-chain steric bulk. This can help physically separate two functional domains in a synthetic peptide or conjugate without introducing strong charge or hydrophobicity from the linker itself.

Flexibility is not equivalent to biological inertness. Gly4 length can change effective reach, intramolecular contact probability and accessibility of attached groups, so linker length should be experimentally optimized in the final construct.

Fmoc-Gly4-OH in Peptide and Conjugate Synthesis

The Fmoc-protected N-terminus supports standard base-labile deprotection, while the free C-terminal acid provides a coupling handle. This architecture allows the Gly4 fragment to be incorporated into larger peptide chains, peptide-drug conjugates, labels, linker systems and other amide-linked constructs.

For shorter or longer spacer screening, compare Fmoc-Gly3-OH and Fmoc-Gly5-OH.

Application Scope

Typical uses include flexible peptide-linker construction, glycine-rich peptide segments, bioconjugation precursors, spacing between pharmacophores or labels, and fragment-based synthesis. Gly-rich sequences also occur in therapeutically relevant peptide and protein constructs, but this building block should be described as a synthetic intermediate rather than as an active pharmaceutical ingredient.

Purchasing and QC Considerations

Gly-rich fragments differ mainly in chain length and terminal protection, so procurement errors can be difficult to detect from names alone. Confirm Gly4 rather than Gly3/Gly5, CAS number, molecular weight, Fmoc protection and C-terminal acid. Lot-specific LC/MS or equivalent identity data are valuable for distinguishing incomplete or over-extended oligoglycine material.

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-Gly-Gly-OH_AS4062

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-Gly4-OH used for?

It is used as a preassembled four-glycine spacer or peptide fragment in peptide synthesis and conjugation workflows.

How is Gly4 different from Gly3 or Gly5?

The number of glycine residues changes spacer length, molecular weight and conformational reach. The optimal length depends on the final construct.

Is Fmoc-Gly4-OH biologically active?

It is primarily a synthetic building block. Biological properties should be assigned to the final purified peptide or conjugate, not to the protected intermediate.

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.

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