Related Experiment Video
Updated: Jan 20, 2026

Energy Dispersive X-ray Tomography for 3D Elemental Mapping of Individual Nanoparticles
Published on: July 5, 2016
A Method for Metal/Protein Stoichiometry Determination Using Thin-Film Energy Dispersive X-ray Fluorescence
Silvia Fruncillo1,2, Matteo Trande3, Christopher F Blanford1,4
1Manchester Institute of Biotechnology , University of Manchester , 131 Princess Street , Manchester M1 7DN , United Kingdom.
Abstract:
A convenient approach is proposed for the quantitation of elemental cofactors in proteins and the determination of metal/protein stoichiometry, on the basis of energy dispersive X-ray fluorescence spectroscopy (EDXRF). The analysis of proteins containing the metals Cu, Fe, Zn, and Ca and also the nonmetallic element P is shown as a demonstration of the generality of the method. In general, the reported method gives limit of detection (LOD) and limit of quantification (LOQ) values in the low ppm range and requires only a few microliters of protein sample at micromolar concentrations. Moreover, sample preparation does not require any digestion steps before the analysis. The expected metal/protein stoichiometry was observed for each protein analyzed, highlighting the precision and accuracy of the method in all the tested cases. Furthermore, it is shown that the method is compatible with multimeric proteins and those with post-translational modifications such as glycosylation.
Related Concept Videos
Chemical Stoichiometry and Gases: Using Ideal Gas Law to Determine Moles
Reaction Stoichiometry
Bonding in Metals
Protein-Drug Binding: Determination Methods
Indirect methods involve isolating the bound drug from its free form in biological samples such as blood, serum, or plasma. These techniques aim to measure the percentage of drugs bound to proteins. Equilibrium dialysis is a commonly used method where the free drug concentration at equilibrium is measured by separating the bound...
X-ray Crystallography
Diffraction
Diffraction is the change in the direction of travel experienced by an electromagnetic wave when it encounters a physical barrier whose dimensions are comparable to those of the wavelength of the light. X-rays are electromagnetic radiation with wavelengths about as long as the distance between neighboring...
Atomic Fluorescence Spectroscopy

