Fluidity One-W

Investigate protein interactions in solution

Fluidity One-W instrument

Fluidity One systems offer a novel approach to determine affinity (KD), size, concentration, and stoichiometric information when a labeled protein interacts with DNA, lipids, antigens or other proteins


  • Analyze protein interactions in aqueous buffer solutions

    Eliminate risk of artefacts
    No surface attachment

  • Determine affinity KD and concentration

    Control for off-target binding and
    false positives

  • Verify the identity of a complex

    Confirm interaction partners via absolute size (hydrodynamic radius, Rh) measurements
    Infer stoichiometry of interaction


Data in agreement with reported literature

PD-1/PD-L1 interaction – critical in control of autoimmune response

A comparison of binding affinity values for PD-1/PD-L1 from a range of biophysical techniques

KD (µM) Technique Reference
4.0 Fluidity One-W
2.2 ITC Cheng et al., JBC (2013)
3.9 SPR equilibrium Zhang et al., Immunity (2004)
0.7 SPR equilibrium Latchman et al., Nat. Imm. (2001)
7.2 MST Magnez et al., Sci. Rep. (2017)

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antibody-affinity in serum - Fluidity One-W Serum (example 1)


Protein-DNA interactions

KD of aptamer-protein interactions

  • No calibration or specialist preparation required
  • KD successfully calculated for each aptamer binding
  • KD values in agreement with reported literature values

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antibody-affinity in serum - Fluidity One-W Serum (example 1)


Reveal changes in molecular conformation

Follow changes in hydrodynamic radius in solution: Protein A:IgG interaction

  • Determine size of SpA:IgG complex in solution
  • Microfluidic diffusion sizing confirmed SpA:IgG 1:3
  • Experimental data in agreement with hypothetical Rh values from molecular modelling (PyMOL*)

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stoichiometry of SpA-IgG


Take a closer look

Fluidity One-W highlights

  • Generate data in close to physiologically-relevant conditions
  • Reduce or eliminate need for time-consuming purification
  • Determine KD and concentration directly in solution
  • Minimize sample consumption – typically 60 – 100 μL per KD
  • Reveal changes in molecular conformation

Fluidity One-W Serum instrument_500x555px

Fluidic Analytics is changing how proteins are characterised

We're doing this with novel, cutting edge technology and a fantastic, committed team

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