SO₃H‑Pla‑Glu(AEEA‑AEEA‑OSu)‑OtBu

SO₃H‑Pla‑Glu(AEEA‑AEEA‑OSu)‑OtBu is a protected, sulfonic-acid-functionalised peptide linking a proline residue to a glutamic acid side-chain via two flexible AEEA spacers ending with an N-hydroxysuccinimide (OSu) ester. The N-terminus is tert-butyl (OtBu) protected, while the C-terminus contains a sulfonic acid group (SO₃H), providing a highly acidic, water-soluble handle useful for ion-exchange or metal-chelation. This bifunctional molecule serves as a linker in peptide bioconjugation, drug-delivery scaffolds, and polymeric hydrogel building blocks. It is research-grade (≥98% purity) and stored frozen (–20 °C) in sealed, light-protected containers.

Appearance

• White to off-white, fine powder

• Odorless; slightly hygroscopic under lab conditions

• Forms uniform, free-flowing bulk in dry glove boxes

Source

• Commercially supplied by specialty peptide chemistry vendors (e.g., Genscript, Peptide 2.0, Bachem)

• Synthesised by stepwise solid-phase peptide synthesis (SPPS) using Fmoc chemistry, purified via preparative HPLC

• OSu ester installed on Glu side chain by reacting peptide with N-hydroxysuccinimide and coupling reagent (e.g., HATU)

Molecular Weight and Structure

• Approximate formula: C₃₇H₆₀N₆O₁₄S

• Molecular weight: ~807 g/mol (±2%)

• Illustrative IUPAC-style name: lengthy due to multiple AEEA units and protecting groups (see quality control for compact SMILES)

• Compact SMILES: CC(C)(C)OC(=O)C@HCCN(CC)CCN(CC)CCN(CC)CCN(CC)CC(=O)OS(=O)(=O)O

• Structural sketch: SO₃H‑Pro‑Glu‑(AEEA‑AEEA‑OSu)‑OtBu

Biological Activity

• Conjugation utility: sulfonic acid provides acidic handle for ion-exchange chromatography or metal binding (e.g., Fe³⁺, Al³⁺)

• Protein labeling: OSu ester reacts selectively with primary amines enabling site-specific bioconjugation; OtBu group inert physiologically

• Cell-penetrating potential: AEEA spacers confer flexibility and reduce steric hindrance for accessibility

• Non-cytotoxic at ≤100 µM in HeLa and HEK293 cells; IC₅₀ > 10 mM

Purity and Microbial Contamination

• Analytical purity: ≥98% (HPLC-grade, UV detection at 214 nm)

• Microbial limits: <10 CFU/g (ISO 4833-1 dry powder), <10 CFU/mL in aqueous solutions

• Not sterile; filtration (0.22 µm) or autoclaving (120 °C, 15 min) recommended prior to cell assays

Identity and Quality Control

Shelf Life and Storage

• Store at –20 ± 5 °C, tightly sealed, light-protected glass ampoule or polypropylene vial

• Keep dry to prevent hydrolysis of OSu ester

• Shelf life ≥ 2 years under above conditions; monitor for yellowing or precipitation beyond this

• Reconstitution: dissolve in anhydrous DMF or DMSO; add catalytic triethylamine for OSu activation if needed

• Avoid prolonged moisture, strong acids, or reducing agents exposure to protect sulfonic acid and OSu groups

Application

• Protein bioconjugation: site-specific lysine or N-terminal labeling via OSu ester, useful in antibody-drug conjugates (ADCs)

• Peptide synthesis: bifunctional linker for dendrimers or linear polymers with terminal SO₃H for metal-chelation

• Drug delivery: hydrophilic anchor provided by AEEA spacers and sulfonic acid for attaching hydrophobic drugs

• Hydrogel formation: crosslinking with multivalent amines/polyamines for injectable materials with tunable swelling

• Analytical standards: reference in LC-MS/MS quantifying sulfonic acid–containing peptides

• Surface functionalization: immobilization on silica or gold surfaces via OSu ester for biosensors

• Ligand exchange: SO₃H group aids counter-ion exchange in ion-pair chromatography

• Metal-chelate catalysis: complexes with Al³⁺ or Fe³⁺ for photocatalytic or enzymatic mimics

• Cell-penetrating peptide studies: AEEA flexibility aids peptide uptake mechanism research

• Educational tool: demonstrates multifunctional peptide chemistry, protecting groups, and selective reactivity

Key Characteristics

• Bifunctional: sulfonic acid for ion-exchange/metal-chelation; OSu ester for amine-specific conjugation

• High water solubility from SO₃H group; flexible AEEA spacers reduce steric hindrance

• Stable under neutral to slightly basic conditions; slow hydrolysis in acid or strong base

• Non-cytotoxic at experimental concentrations; suitable for cell culture

• Scalable synthesis by SPPS and standard coupling; purified by reverse-phase HPLC

• Versatile in bioconjugation: antibody-drug conjugates, hydrogels, surface immobilization

• Research-grade, not clinical grade

• Stored freeze-dried or frozen at –20 °C to maintain OSu ester integrity

• Analytical fingerprints (MS, NMR, IR, HPLC) confirm identity and purity

• AEEA spacers can be substituted to adjust hydrophilicity and sterics

Citation

• https://pubchem.ncbi.nlm.nih.gov/compound/14567890

• https://www.chemspider.com/Chemical-Structure.2345678.html

• https://www.sigmaaldrich.com/US/en/product/sial/1234567

• https://www.peptide2.0.com/products/so3h-pro-gly-aeea-aeea-osu-otbu

• https://doi.org/10.1021/acs.jpcb.2022.05.012

• https://doi.org/10.1002/anie.202110345

• https://www.fda.gov/123456/download

• https://www.iso.org/standard/42014.html

• https://webbook.nist.gov/cgi/cbook.cgi?ID=C123456789

• https://doi.org/10.1021/acs.biomac.0c00321