Quick, reliable assessment of protein size even at low concentration

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Assessment of protein size can provide valuable insights in a variety of applications and enable go/no-go decision making prior to time consuming and expensive downstream analyses.

The Fluidity One combines label-free measurement, high sensitivity detection and intuitive, plug and play design for rapid analysis of protein state at low concentrations, even in detergents.

How does Fluidity One work?

The Fluidity One measures the rate of diffusion of proteins under steady state laminar flow in a microfluidic system. To do this, a stream of your protein of interest is introduced alongside an auxiliary stream. Because there is no convective mixing the only way your 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.

The quantity of protein in each stream is then determined using an amine reactive fluorogenic dye.  The combined total fluorescence is used to determine the concentration of protein in solution, and the ratio of fluorescence between the two streams used to determine the diffusion co-efficient of the protein, which in turn is used to determine the protein’s hydrodynamic radius.

Because diffusion occurs while the protein is in its native state, the reported size is that of the native protein in solution. And because this process all takes place in microfluidic volumes, the measurement can be performed quickly and with minimal sample input.

Watch the full video here.

With Fluidity One
  • Get more for less

    Gain meaningful quality insights from hydrodynamic radius (Rh) and concentration in a single read, with less sample and in less time.

  • Look at the hard stuff too

    Solution state measurement coupled with high sensitivity means you can study proteins that are problematic for other systems.

  • Pipette, plug, play

    The minimal sample prep, easy-to-use design and wide dynamic range means you can skip lengthy setup and get to the results faster.

  • Let us do the work

    Pre-configured just for proteins, with no calibration required, allowing you to focus on data generation rather than setup.

  • No technician

    Intuitive design, straightforward consumable management and automated analysis means minimal training and no technical oversight required.

  • No IT department

    Fully integrated user interface and over-the-air software updates mean no IT team needed to troubleshoot peripherals.

Want to see it for yourself?

If you're interested to see how the Fluidity One could help your research, we're happy to talk about your work and arrange a demonstration on your site.

More insights with less

Size determination MDS DLS TDA

From small peptides to large complexes

Using just 5 µL sample, Fluidity One can report hydrodynamic radius values for a range of different size proteins, giving equivalent values to DLS and TDA (Viscosizer).

See further details on the full application note here.

Accurate measurements at low concentrations

Fluidity One can provide reliable sizing, even at low concentration when other methods are no longer accurate.

See the full experimental data on our application note here.

Size determination of BSA at varying concentrations MDS DLS TDA

Fluidity One Key Features

The combination of label-free measurement, high sensitivity detection and intuitive, plug and play design make the Fluidity One perfect for rapid analysis of protein state at low concentrations, even in detergents.

  • In-solution determination of size and concentration in a single measurement using Microfluidic Diffusional Sizing (MDS)
  • Label free measurement
  • Minimal setup as no calibration required
  • Low sample requirement – use as little as 50 ng per measurement
  • High reproducibility and accuracy (even at low concentrations)

  • Convert Rh to molecular weight (Mw) using inbuilt calculator
  • Easy-to-use interface and consumable management
  • Disposable single use chips and contained waste 
  • Over the air software updates deliver ongoing system improvements
  • Manufactured under ISO 9001 quality management system

What our customers say

Fluidity One has quickly gained popularity within the biophysics and biochemistry community, with labs using it to further their research in a wide range of fields.

Find the latest reviews here, or submit your own review with Select Science.


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Application notes

  • Application note31 October 2018

    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 note22 August 2018

    Oligomerization of Interleukin-2

    A commercially available human interleukin-2 is assessed by microfluidic diffusional sizing on the Fluidity One across a dilution series. The hydrodynamic radius is observed to increase with increasing concentration, in a way which suggests a monomer-trimer equilibrium with positive cooperativity is established.

  • Application note22 August 2018

    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.

  • Application note10 May 2018

    Detecting insulin oligomerization using microfluidic diffusional sizing

    Insulin monomers self-assemble into hexamers, which is known to affect its level of uptake in the human body. Here we show that Microfluidic Diffusional Sizing (MDS) can be used to detect these changes.

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Fluidic Analytics is changing how proteins are characterised

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