Data sheets | SPR Sensor chips

SpyCatcher–modified sensor chips

XanTec’s SpyCatcher (SPY) sensor chips are coated with a bioinert (poly)carboxylate matrix pre-functionalized with recombinant 12.8 kDa SpyCatcher3™. Immobilized SpyCatcher3 forms a highly stable covalent isopeptide bond with Spy-tagged proteins under physiological conditions (pH 5–8, 4–37 °C), enabling site-directed and permanent ligand immobilization.

Compared with the widely used streptavidin/biotin system, the SpyCatcher/SpyTag technology offers two major advantages. First, the interaction is truly covalent, resulting in exceptional long-term stability and drift-free baselines. Second, SpyCatcher3 is considerably smaller than streptavidin, occupying less volume within the hydrogel matrix and allowing higher ligand capture densities. These properties make SPY sensor chips particularly attractive for applications involving short peptides, small molecules, and fragments.

SPYD200M and SPYHC200M sensor chips provide high immobilization capacities for dense ligand presentation, while SPYP sensor chips combine lower capacity with excellent diffusion characteristics typical of 2D coatings. This makes SPYP surfaces especially suitable for protein–protein interaction studies and systems with fast association and dissociation rates.

Key features:

Fast assay development: No preconcentration or chemical activation required; ligand immobilization occurs directly under physiological conditions.
Exceptional stability: Covalent SpyCatcher/SpyTag coupling ensures permanently immobilized, drift-free ligands.
Oriented immobilization: Site-directed attachment via N- or C-terminal SpyTag maximizes ligand activity.
Versatile capture capacity: Available on CMDP, CMD, and HC base coatings to match specific experimental requirements.

Schematic illustration of a 3D SPY sensor chip. Red dots represent negatively charged carboxyl groups along the green polymer chains. The magnified view shows immobilized SpyCatcher (red) covalently binding a Spy-tagged protein ligand (SpyTag in blue, protein ligand in yellow).²

Product code	SPYP	SPYD200M	SPYHC200M
Base coating	2D, ultra-short CM-dextran (high density)	3D, 200 nm bioinert CM-dextran (medium density)	3D, 200 nm bioinert polycarboxylate (medium density)
Capture immobilization capacity [µRIU]³	≈ 100	≈ 500	≈ 500
Recommended ligands	Spy-tagged peptides and proteins
Recommended analytes	proteins peptides nucleic acids viruses and cells	proteins peptides nucleic acids small molecules	proteins peptides nucleic acids small molecules carbohydrates
Intended purpose	immobilization of Spy-tagged proteins kinetics of medium and large analytes especially suitable for weak binders with fast on- and off-rates	immobilization of Spy-tagged proteins kinetics of medium and small analytes equilibrium and concentration analysis high capture densities	immobilization of Spy-tagged proteins kinetics of medium and small analytes including carbohydrates equilibrium and concentration analysis high capture densities

¹ SpyCatcher3 carries a His-tag that may interact with certain ligands or analytes.

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 Based on capture of 100 nM SpyTag, with 1 µRIU corresponding approximately to 1 RU.

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SpyCatcher–modified sensor chips