How much sample do you need to measure binding affinity and size?
FIDA (Flow Induced Dispersion Analysis) works with sample sizes from nanolitres to microlitres, down to 2 µL in the newest Fida model. How much analyte you need depends on the assay setup and on the affinity of the interaction, and the remaining sample can be retrieved after the measurement.
How much sample does a FIDA measurement consume?
Sample consumption in FIDA depends on the assay setup. For standard binding assays, a low nM range indicator is used, and the concentration of analyte needed will depend on the affinity of the interaction. For sample quality control, a µM range indicator is measured with the buffer as analyte. The sample requirements of each assay format are listed in Which FIDA assay format should you use?
What is the volume consumed by FIDA per sample?
FIDA works with sample sizes from nanolitres to microlitres, as listed in the Fida instruments comparison table. Naturally, the consumption varies by application.
In the newest Fida model, you can sample from as little as 2 µL in a well, and a single run consumes around 40 nL of the fluorescent sample, as explained in the webinar The new Fida Instrument: Fida Evolve: how does it differ and what do the users think?
Can I do triplicate measurement from the same sample preparation?
Yes, technical replicates from the same sample preparation can be performed by assigning the desired replicate count in the software interface. The only requirement is the availability of sufficient analyte solution for replicate runs.
Can the sample be reused?
Yes. Thanks to the thermally regulated sample loading chamber on the Fida instrument, a loaded set of samples can be incubated at the desired temperature for the entire duration of the measurement. After the measurement, the remaining sample volume can be retrieved from the loading chamber. This setup allows for sample savings.
For example, in the application note High throughput detergent screening for membrane proteins, 12 detergents were screened in triplicate using only 120 nL of crude protein solution for three replicates, and the whole leftover volume of about 19.8 µL, out of 20 µL loaded, was recovered for further experiments.
What are examples of FIDA measurements with low sample use?
In a Capmix assay, only 40 nL of indicator is used per data point, which adds up to 1.4 µL of sample for a 12 point titration in triplicate, as described in the Assay formats course in the Affinity section of the Fidabio Learning Hub. In the application note Rapid Sizing And Characterization of Bispecific Antibodies using nL of Sample, the size of the free antigen and of the binary and ternary complexes was measured using only 120 nL for a triplicate measurement.
In the publication Quantification of Structural Integrity and Stability Using Nanograms of Protein by Flow-Induced Dispersion Analysis (Molecules, 2022), protein stability and unfolding were quantified using only 40 ng of protein per data point.
In the publication Continuous Titration Based Method for Rapid In-Solution Analysis of Non-Covalent Interactions (Chemistry Methods, 2025), a KD was measured in as little as 45 seconds, using only nanograms of protein.
In the publication In-solution Characterization of Biomolecular Interaction Kinetics under Native Conditions (Analytical Chemistry, 2025), binding kinetics were measured from nanolitre to nanogram amounts of sample.
In the publication Flow-Induced Dispersion Analysis for Probing Anti-DsDNA Antibody Binding Heterogeneity in Systemic Lupus Erythematosus Patients (Analytical Chemistry, 2016), autoantibody binding in patient plasma was detected within minutes, using only a few hundred nanolitres of sample.
Frequently asked questions
How much indicator does a FIDA measurement use?
Nanolitres to microlitres, depending on the assay. The indicator concentration is in the low nM range for binding assays and in the µM range for sample quality control.
Does a thinner capillary use less sample?
Yes. The capillary size page explains how capillary dimensions affect sample use.
Related resources
New to binding assays? How to perform a binding affinity assay? walks through a binding measurement, What is KD (dissociation constant)? explains why the analyte concentration depends on the affinity, and the binding affinity readout shows what a run reports. To find out how much sample your project would need, book a discovery call.
