Is my protein interacting?

Protein function is often determined by its interactions. From lipids, to nanobodies, ligands, DNA or even self-interaction in oligomerization or aggregation – the species a protein interacts with and the nature of these interactions, unlock valuable insights. Observe these interactions in solution and in native conditions using the Fluidity range.

How do we measure interactions?

Changes in binding state can be inferred from changes in protein size. To study changes in size we use Microfluidic Diffusional Sizing, which measures the rate of diffusion of proteins under steady state laminar flow in a microfluidic system.

To do this, a stream of protein of interest is introduced alongside an auxiliary stream. Because there is no convective mixing the only way the protein can migrate into the auxiliary stream is by diffusion, the rate of which will depend on the size of the protein. Small proteins will diffuse very rapidly, and large proteins more slowly. Diffusion can occur at any point along the length of the diffusion chamber, but at the end the streams are re-split, and at this point the degree of diffusion is fixed. Protein is then quantified in each stream, and the ratio used to determine the diffusion co-efficient of the protein, which in turn is used to determine the protein’s hydrodynamic radius. 

Protein-non-protein interactions with Fluidity One

In the Fluidity One, the protein is detected using an amine reactive fluorogenic dye. This means that any non-amine containing species, such as lipids, oligonucleotides or polymers will not be detected on this system. Nevertheless changes in size caused by binding to one of these species can be observed, making the Fluidity One well suited for quick analysis of protein-non-protein interactions.

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Protein-protein interactions with Fluidity One-W

With the Fluidity One-W you can assess on-target interactions even in crude biological backgrounds. Because pre-labeled fluorescent proteins are measured,  binding events of a particular species of interest can be studied, even in crude lysates. Critically because size provides insights into identity, off-target binding events and false positives can be controlled for on Fluidity One-W.

Ready for a demo?

Speak to a member of our team to discuss your applications for the Fluidity One and organising a demo.

Fluidity One in use

Application notes

  • Application note

    Protein Size as an Indication of Structure

    Molecular weight (Mw) is a commonly used, and for many scientists a readily understood, parameter to describe the size of a protein or complex. Here we show how hydrodynamic radius (Rh) can be used in combination with Mw to provide insights into the shape and structure of proteins and illustrate how Mw alone may not always provide a complete picture.

  • Application note

    Interleukin-2 stability in changing buffer and temperature conditions

    The stability of interleukin-2 in different buffers and storage temperatures is evaluated using the Fluidity One. We find that IL-2 forms aggregates within 24 hours in some buffers, and that the Fluidity One provides a simple means to evaluate the stability of proteins across different conditions.