Fmoc-Gly-Ser[psi(Me,Me)pro]-OH is an Fmoc-protected Gly-Ser pseudoproline building block for solid-phase peptide synthesis (SPPS). The Ser residue is incorporated in a reversible 2,2-dimethyloxazolidine pseudoproline form that temporarily changes local backbone hydrogen-bonding and conformation during chain elongation.

The preformed Gly-Ser unit introduces the sequence motif in one coupling operation. Under standard TFA-mediated final cleavage and deprotection, the acid-labile pseudoproline ring is opened and the native Ser residue is regenerated.

Product Information

Why the Gly-Ser Motif Is Distinct

Gly contributes minimal side-chain steric demand, while the Ser pseudoproline creates the conformational interruption. This combination can be useful when a flexible Gly-Ser segment sits near a region that becomes aggregation-prone later in chain elongation. This should be considered alongside solid-phase peptide synthesis guide when diagnosing sequence-dependent assembly problems.

Backbone Disruption Without a Bulky Upstream Residue

The value of this reagent is not extra hydrophobic shielding or side-chain protection. Its main synthetic function is the temporary Ser-derived oxazolidine, which changes local backbone geometry and reduces the continuity of peptide-peptide hydrogen-bonding patterns.

Coupling and Native Ser Recovery

The protected Gly-Ser unit is introduced as one fragment. Standard TFA-mediated cleavage opens the pseudoproline ring and regenerates Ser. This makes the reagent suitable when the final sequence must retain an unmodified Gly-Ser motif.

Selection Considerations

A Gly-Ser motif alone is not evidence that a pseudoproline is required. We would prioritize it when the broader sequence shows aggregation, poor solvation, or a reproducible synthesis bottleneck near the planned insertion site. Related motifs can be compared in the protected pseudoproline building blocks.

Experimental Planning

When a difficult sequence contains several possible Ser/Thr pseudoproline insertion sites, placement should be assessed together with chain length, hydrophobicity, resin loading, neighboring residues, and the stage at which coupling or deprotection performance begins to decline. The presence of a Gly-Ser motif alone does not establish that this building block is required.

For projects where building-block selection needs to be evaluated with the full target sequence, our modified peptide synthesis can support integrated planning, synthesis, purification, and QC requirements.

Product Documents

MSDS - Fmoc-Gly-Ser[psi(Me,Me)pro]-OH (AS4024)

The Safety Data Sheet provides product identification, hazard information, handling and storage guidance, exposure controls, transport information, and regulatory information for laboratory use.

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 psi(Me,Me)pro indicate?

It denotes a dimethyl-substituted pseudoproline formed from the downstream Ser residue. The five-membered oxazolidine temporarily changes backbone behavior during synthesis.

Why is the Gly-Ser unit supplied as a preformed building block?

The amide bond immediately before the pseudoproline nitrogen is already formed, avoiding direct acylation of a sterically hindered oxazolidine nitrogen and allowing the motif to be introduced in one coupling operation.

Does the pseudoproline remain in the final peptide?

No. Standard TFA-mediated final cleavage opens the pseudoproline ring and restores the downstream Ser residue.

Should this be used for every Gly-Ser sequence?

No. Pseudoproline use is most justified when the sequence shows aggregation, poor chain accessibility, or another reproducible assembly problem. Straightforward sequences may not require it.

Research Use Only.