Metalloproteins play a key role in the progression of many diseases. Using ion beam analysis through particle-induced X-ray emission (PIXE) and anomalous X-ray analysis we have quantitatively identified the metal atoms in 30 previously structurally characterized proteins using minimal sample volume leading to new mechanistic knowledge. The details are published in a paper entitled “High-Throughput PIXE as an Essential Quantitative Assay for Accurate Metalloprotein Structural Analysis: Development and Application” by Geoffrey W. Grime, Oliver B. Zeldin, Mary E. Snell, Edward D. Lowe, John F. Hunt, Gaetano T. Montelione, Liang Tong, Edward H. Snell, and Elspeth F. Garman in JACS. Over half of these metals had been misidentified in the deposited structural models. Some of the PIXE detected metals not seen in the models were explainable as artifacts from promiscuous crystallization reagents. For others, using the correct metal improved the structural models. For multinuclear sites, anomalous diffraction signals enabled the positioning of the correct metals to reveal previously obscured biological information. PIXE is insensitive to the chemical environment, but coupled with experimental diffraction data deposited alongside the structural model it enables validation and potential remediation of metalloprotein models, improving structural and, more importantly, mechanistic knowledge.
PIXE identifies metals and provides new structural information
