Fmoc-Gly-Gly-Gly-Gly-Gly-OH, also described as Fmoc-Gly5-OH or Fmoc-pentaglycine, is a preassembled five-glycine peptide fragment with an Fmoc-protected N-terminus and a free C-terminal carboxylic acid. It provides a defined Gly₅ segment for peptide-linker construction, flexible spacer design and synthesis of glycine-rich motifs.

Five consecutive glycine residues create a highly flexible, minimally side-chain-bulky segment. The building block can be useful when a project requires a fixed pentaglycine unit and the researcher wants to avoid four additional glycine-coupling cycles needed to build the same motif residue by residue.

Product Information

Pentaglycine as a Flexible Peptide Spacer

Glycine lacks a side-chain carbon, reducing steric bulk around the peptide backbone. Consecutive glycine units are therefore frequently selected when the design objective is flexibility and spatial separation rather than introduction of a hydrophobic, charged or bulky side chain.

A Gly₅ segment can be incorporated into peptide conjugates, fusion-inspired synthetic constructs and linker architectures where distance between functional elements is important. The exact effect on activity, stability or proteolysis remains context-dependent and should be evaluated in the final construct rather than assumed from the spacer alone.

Fmoc-Gly5-OH vs Gly3 and Gly4 Building Blocks

Alan Scientific also supplies shorter preassembled glycine fragments such as Fmoc-Gly-Gly-Gly-OH (Gly3) and Fmoc-Gly-Gly-Gly-Gly-OH (Gly4).

The difference is not simply molecular weight. Spacer length changes the number of backbone amides, overall reach and conformational freedom of the final construct. Gly3, Gly4 and Gly5 should therefore be selected according to the required architecture rather than treated as interchangeable linkers.

Application Scope

Fmoc-Gly5-OH can be used in SPPS or fragment-based peptide synthesis for flexible spacers, glycine-rich peptide segments, linker optimization, conjugation precursors and construction of defined pentaglycine motifs.

Pentaglycine motifs also appear in biological systems and enzyme-recognition research, but this protected building block should not itself be assumed to be an enzyme substrate. Recognition depends on the complete final molecular context, terminal chemistry and neighboring residues.

Purchasing and QC Considerations

Because the sequence contains only glycine, stereochemical ambiguity is minimal; however, identity still depends on correct chain length, Fmoc protection and free C-terminal acid. Mass alone is not sufficient to distinguish partially assembled Gly-rich fragments. Lot-specific analytical data and COA should therefore be reviewed.

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-Gly-OH_AS4061

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-Gly5-OH used for?

It is used as a preassembled pentaglycine fragment for flexible peptide spacers, linker construction and glycine-rich peptide synthesis.

Why use a preassembled Gly5 fragment?

It can reduce the number of individual glycine-coupling cycles and gives a defined five-residue linker segment before incorporation into a larger construct.

Is Gly5 always better than Gly3 or Gly4?

No. Longer glycine spacers provide greater length and flexibility, but the optimal spacer depends on the final conjugate or peptide architecture.

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.