FIDA, or Flow Induced Dispersion Analysis, is a technology that addresses the measurement of non-globular proteins without making any structural assumptions about the molecules. This unique approach sets FIDA apart, as it doesn't rely on a priori knowledge of the molecular structure. Instead, FIDA measures the hydrodynamic radius (Rh) of species, which can be both globular or non-globular, including intrinsically disordered or partially unfolded proteins.
The core principle of FIDA is the utilization of Taylor’s dispersion (diffusion) profiles. This approach allows FIDA to study a wide range of molecular shapes and conformations, making it a versatile tool in the analysis of diverse biomolecules. The measurement of Rh, which represents the effective hydrodynamic size of the molecule, is a key parameter in FIDA.
The Stokes-Einstein equation, a fundamental concept in statistical physics, forms the basis of FIDA technology. This equation establishes a relationship between the diffusion coefficient (D) of a particle in a fluid, the Boltzmann constant (k), the absolute temperature (T), the viscosity of the solvent (η), and the particle's hydrodynamic radius (Rh). By utilizing this equation, FIDA can determine the hydrodynamic radius (Rh) of non-globular proteins and other molecules, providing valuable insights into their size and behavior in a solution.
By definition, the hydrodynamic radius is defined as the radius of a hypothetical sphere that diffuses at the same rate as the particle or molecule in question, under the same conditions (Einstein, 1905). In the context of FIDA, this concept is extended to molecules with various shapes and structures, including non-globular proteins. FIDA's ability to measure Rh without assuming a specific molecular structure makes it an invaluable tool for characterizing and studying a wide range of biomolecules, contributing to scientific research in the field of molecular biology and biotechnology.