FIDA stands for Flow Induced Dispersion Analysis. It is a first-principle based, in-solution technology, which provides a precise, quantitative, and highly robust method to determine how changes to an analyte affect the analyte. The changes that may be assessed are numerous ranging from adding a binding partner to changes in the environments including ionic strength, pH, buffers and different crude matrixes, temperature etc. The typical readout is hydrodynamic radi which provides information about quantity, affinity, sample integrity, changes in oligomeric state, aggregation, stoichiometry etc.

FIDA is based on first principles of physics and fluid mechanics of a laminar flow and Taylor dispersion.

FIDA technology takes advantage of these two principles by measuring fluorescence of particles in the laminar flow and analysing their dispersion over time. Following signal analysis, gives rise to an accurate assessment of molecular diffusivity and hydrodynamic radius. For instance, the change in the apparent hydrodynamic radius of a binder in the presence of its ligand reflects the strength of the interaction.

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Watch the video above. There, you can see a tiny round microfluidic channel. Initially your sample is a plug at the inlet of the channel, but due to the flow and diffusion it evolves into a parabolic profile. The shape of your sample is governed by your samples diffusivity or hydrodynamic radius. The sample is measured by fluorescence. Although the fluorescence gives a lot valuable information in itself (see Fida readouts chapter), for now, we just focus on the peak shape. As the illustration below shows the peak shape is related to the size of your molecule as it is governed by radial diffusivity.

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Small molecules diffuse faster, creating sharp, narrow peaks, while larger molecules diffuse more slowly, resulting in broader peaks.‍

Let's see some examples:‍

Amino Acid (tiny size e.g., glycine): Moves very fast → sharpest peak

Peptide (small chain, e.g., insulin): Slower than amino acids → moderate peak width

Protein (large folded structure, e.g., hemoglobin): Moves the slowest → broadest peak

Thanks to fluorescence-based diffusivity measurement, with some simple math you can now obtain the hydrodynamic radius. The good news is that it is all done in the software, so we won't be diving into the details here. If you are interested you can access our e-learning platform here.

And what does this measurement give you?Once you can measure the hydrodynamic radius you can do many interesting assays, such as binding and interaction studies, aggregation, oligomerization, confromational changes, sample purity test.For example a you can do binding curve by titrating with a ligand and observing the change in hydrodynamic radius. This makes FIDA widely used across life sciences, food industry, and even mining.

What does it mean that FIDA is a "first principle technology"? First principle means that FIDA:

1. Relies on basic laws of nature
2. Is absolute
3. Does not require calibration

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