Novel Bioaffinity-MS Tandem System Developed

Researchers at the University of Konstanz, have for the first time successfully developed a novel on-line bioaffinity-electrospray ionisation (ESI) mass spectrometry approach, which enables the simultaneous label-free detection, identification and quantification of protein–ligand interactions. Combining the sam5™ surface acoustic wave (SAW) biosensor from SAW Instruments directly with ESI-MS has enabled the direct connection of protein-ligand KD analysis with their subsequent quantification and structural characterisation by mass spec.

This new tandem SAW-ESI-MS system has been developed in the laboratory of Professor Michael Przybylski at the University of Konstanz and recently published. Biosensors have previously only ever been connected to mass spec indirectly in a MALDI-TOF format where crystallised sample spots are analysed. The new system is unique, as the first that directly connects liquid flow from the SAW biosensor directly into the ESI-MS via a standard desalting interface – an approach impossible with other available biosensors. This novel set-up enables direct quantitative determinations of protein-ligand complexes by SAW-yielded dissociation constants (KD) from low nanomolar to sub-micromolar sample concentrations.

The Przybylski team observed the key advantages of SAW in comparison to classical immuno-analytical bioaffinity techniques to be the direct and rapid determination of association/dissociation constants from small and dilute sample amounts, without the need for labelling or recalibration for buffer changes. Furthermore, the sam5 biosensor is able to make detection measurements in complex biological samples e.g. crude brain samples, blood or cell lysates.

The new SAW-ESI-MS technique has been successfully applied by the Przybylski group to a number of clinically relevant applications for biomarker discovery, analysis and epitope mapping. These include human ß-amyloid peptides (Alzheimer’s Disease), Substance P peptidecalmodulin complex, tyrosine-nitrated peptides (neurotoxic events) and human ßsynuclein (Parkinson’s Disease). Indeed, no details on affinity binding and KD determination of the anti-α-synuclein-human α-synuclein complex have previously been reported.

The sam5™ biosensor instrument from SAW Instruments is a unique tool for advanced real-time biomolecular interaction and kinetic studies. The sam5™ is a peerless biosensor utilising Surface Acoustic Wave (SAW) technology for the label-free detection of real-time binding and structural events. XA