CMPEG–modified sensor chips
XanTec’s CMPEG sensor chips (not to be confused with CMPG) are based on short, 4 kDa carboxymethyl-terminated polyethylene glycol (PEG) chains grafted onto a hydrophilic adhesion promoter on a gold support. Ligands can be covalently attached via their amine groups using EDC/sulfo-NHS-based coupling chemistry1, enabling immobilization of proteins, antibodies, peptides, nucleic acids, carbohydrates, and small molecules.
Because PEG chains terminate in a single reactive carboxyl group, protein immobilization capacity is limited to a near-monolayer and is therefore relatively low (typically ~1,000–2,000 µRIU). At the same time, this minimal and well-defined surface architecture provides a high degree of conformational freedom for immobilized ligands, helping to preserve biological activity. The amphiphilic PEG backbone reduces nonspecific binding.
CMPEG sensor chips are frequently requested because PEG is considered a bioinert coating, particularly when dextran-based derivatives such as CMD cannot be applied. However, alternative XanTec coatings (e.g., HCP, CMTEG, CMPG) may offer superior performance in applications requiring maximum surface inertness, as CMPEG surfaces can exhibit elevated nonspecific adsorption under certain conditions.
Key features:
- Well-known sensor matrix: Short CMPEG brush with well-characterized surface chemistry and moderate nonspecific binding, including for highly cationic biomolecules.
- Versatile ligand coupling: Supports covalent attachment via established EDC/sulfo-NHS chemistry.
- Low sensor-matrix profile: Terminally exposed carboxyl groups maximize ligand accessibility and support high ligand activity despite low immobilization capacity.
- No polysaccharide backbone: Absence of carbohydrate motifs prevents unintended interactions with lectins and other carbohydrate-binding biomolecules.
| Product code | CMPEG |
|---|---|
| Base coating | Dense 4 kDa PEG polymer brush with terminal carboxyl groups |
| Electrostatic preconcentration capacity [µRIU]3 | ≈ 1,000–2,000 |
| Recommended ligands |
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| Recommended analytes |
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| Intended purpose |
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1 Use of sulfo-NHS is recommended for efficient protein coupling due to the low surface charge density of CMPEG coatings.
2 All illustrations are schematic representations and are not drawn to scale; dimensions, densities, and spatial relationships do not reflect actual physical or chemical proportions.
3 Preconcentration capacity determined by injecting 100 µg/mL BSA in 5 mM sodium acetate pH 5.0, with 1 µRIU corresponding to ≈ 1 RU. Maximum covalent coupling efficiencies typically span ≈ 20–45% of the electrostatic preconcentration capacity and depend strongly on protein properties.