How does Fida Instrument detect a signal?
The FIDA instrument detects molecular signals using fluorescence, a well-established method in biophysical analysis. A fluorescent signal must be present in the sample, either from an external label or from the molecule’s intrinsic fluorescence (label-free).
Detection Channels
The instrument is equipped with detectors that can capture emission across multiple wavelengths: 480 nm, 550 nm, 640 nm, and 280 nm. This flexibility allows different fluorophores or intrinsic signals to be monitored without requiring extensive sample modifications.
Excitation and Detection Principle
FIDA uses LED excitation as the light source. The emitted fluorescence is then amplified through photomultiplier tubes (PMTs), ensuring high sensitivity. Unlike laser-based instruments, FIDA does not heat the sample during measurement, which helps preserve the native structure and dynamics of proteins and other biomolecules.
Orthogonal Readouts
One of the strengths of the FIDA approach is that it delivers three complementary readouts from the same experiment:
- Absolute size (hydrodynamic radius): Determined from Taylor dispersion and the Stokes–Einstein relation.
- Binding-Related Intensity Change (BRIC): Monitors fluorescence intensity shifts during binding interactions.
- FIDA Lambda Dynamics: Detects wavelength (lambda) shifts in fluorescence, which occur when binding events alter the environment of the fluorophore or other optical markers.
Summary
By combining LED excitation, sensitive PMT detection, and multiple wavelength channels, the FIDA instrument provides reliable, label-free or label-based fluorescence signals. This design enables precise measurement of molecular size, binding interactions, and spectral changes, all under near-native conditions.
