Protein

In the field of proteomics, one has to deal with a class of molecules with diverging and in several aspects still unpredictable properties. It is quite undesirable to have to modify proteins with labels before being able to characterize them. Obviously, under such circumstances label-free detection methods are strongly favoured.Surface plasmon resonance spectroscopy is the most common label-free technique. However, a gold layer is needed on the solid support which has to be produced under highest standards. Current applications are in most cases restricted to a few regions of interest. Protein arrays on standard glass slides cannot be read out or even be characterized kinetically.

Bo Liedberg and colleagues demonstrate a chip platform for the adresseable immobilization of protein-loaded vesicles on a microarray for parallelized high-trough put analysis of lipid-protein systems. Imaging surface Plasmon resonance in ellipsometric mode, performed with an EP³ SE was used to monitor vesicle immobilization, protein tethering, protein-protein interaction and chip regeneration.

The imaging ellipsometer was equipped with an SPR-cell in Kretschmann configuration. Images of the surface were taken at indicated times and difference images were produced. The change of mass was recorded in correlation to the ellipsometric parameter Delta – in parallel at different regions of interest on the array.

Reference:

Klenkar G, Brian B, Ederth Th, Stengel G, Höök F, Piehler J, Liedberg B (2008) Addressable adsorption of lipid vesicles and subsequent protein inter¬action studies. Biointerphases 3: 29-37.

Valiokas R, Klenkar G, Tinazli A, Reichel A, Tampe R, Piehler J, Liedberg B (2008) Self-Assembled Monolayers Containing Terminal Mono-, Bis-, and Tris-nitrilotriacetic Acid Groups: Characterization and Application. Langmuir 24: 4959-4967.

Valiokas R, Klenkar G, Tinazli A, Tampe R, Liedberg B, Piehler J (2006) Differential Protein Assembly on Micropatterned Surfaces with Tailored Molecular and Surface Multivalency. ChemBioChem 7, 1325 – 1329

A protein array chip for label-free optical detection of low molecular weight compounds has been developed in . As a proof of principle, the chip is proven capable of rapidly  determining hits from aqueous cocktails composed of four common narcotics, cocaine, ecstasy, heroin, and amphetamine, using imaging surface plasmon resonance (SPR) as the detection principle, using the EP³-SE.

The chip is produced by the self organisation of injected antibodies to a pattern of immobilized narcotic derivatives. The narcotics in the analyt solution displace the immobilized derivatives in the recognition side of the antibodies and remove them from the surface

For proof of principal, the chip is proven capable of rapiditly determining hits from aqueous coctails of commen narcotics.