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Protein aggregate-ligand binding assays based on microfluidic diffusional separation

Authors: Yingbo Zhang, Alexander K. Buell, Thomas Müller, Erwin De Genst, Justin Benesch, Christopher M. Dobson, and Tuomas P. J. Knowles

Chembiochem, 2016, 17 (20), 1920-1924. DOI: 10.1002/cbic.201600384

 

Abstract

Zhang et al., again demonstrate the utility of Microfluidic Diffusional Sizing (MDS) to monitor Nanobody binding to ɑ-synuclein, but this time also use MDS to monitor α-synuclein fibril formation. Due to their size, α-synuclein fibrils diffuse very little and are retained in the centre of the channel, while α-synuclein monomers diffuse more freely. The authors observe that after 40 minutes, fluorescence signal corresponding to the monomeric protein was found to increase in the centre of the channel as a consequence of incorporation into aggregates (Figure 1).

Fluorescence intensity profiles across the channel J) Decrease of free monomer signal outside the bright central region over time during the growth of fibrils.
Figure 1: Monitoring fibril formation using MDS  i) Fluorescence intensity profiles across the channel. j) Decrease of free monomer signal outside the bright central region over time during the growth of fibrils.

The measurement of molecular interactions with pathological protein aggregates, including amyloid fibrils, is of central importance in the context of the development of diagnostic and therapeutic strategies against protein misfolding disorders. Probing such interactions by conventional methods can, however, be challenging because of the supramolecular nature of protein aggregates, their heterogeneity, and their often dynamic nature.

Here they demonstrate that direct measurement of diffusion on a microfluidic platform enables the determination of affinity and kinetics data for ligand binding to amyloid fibrils in solution. This method yields rapid binding information from only microlitres of sample, and is therefore a powerful technique for identifying and characterising molecular species with potential therapeutic or diagnostic application.

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Instrument: Fluidity One
Therapeutic area: amyloid, protein-protein interaction

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