Quantification of Trace Elements in Protein Bands Using Synchrotron Radiation X-ray Fluorescence after Electrophoretic Separation

Metalloproteomics: challenges and prospective for clinical research applications

Metals are essential cofactors, utilized in many critical cellular processes. For example, zinc is important in insulin biosynthesis and may play a role in Alzheimer's disease, but much of how the zinc-mediated process remains unknown. Knowing which metal is in which protein at a given point in time would lead to new insights into how metals work in biological systems. New tools are being developed to investigate the biochemistry and cell biology of metals, with potential for biomedical applications. In this report, we consider the promise and limitations of metalloproteins detection techniques. We provide a brief overview of the techniques available and a discussion of the technical challenges to biomedical applications, with particular focus on what must be overcome for the potential of these approaches to be achieved.

Electrophoretic separation and detection of metalloproteins by X-ray fluorescence mapping

All living systems depend on metalloproteins. Yet, while tools for the separation and identification of apo-proteins are well developed, those enabling identification and quantitation of individual metalloproteins within complex mixtures are still nascent. Here, we describe the electrophoretic separation of a mixture of carbonic anhydrase, ceruloplasmin, urease, and hemoglobin using native 2D gel electrophoresis and X-ray fluorescence mapping-an approach we have developed to be broadly applicable, not require specialized equipment for sample preparation, and likely to be extensible in the future.

Imaging metals in proteins by combining electrophoresis with rapid x-ray fluorescence mapping

Growing evidence points toward a very dynamic role for metals in biology. This suggests that physiological circumstance may mandate metal ion redistribution among ligands. This work addresses a critical need for technology that detects, identifies, and measures the metal-containing components of complex biological matrixes. We describe a direct, user-friendly approach for identifying and quantifying metal-protein adducts in complex samples using native- or SDS-PAGE, blotting, and rapid synchrotron X-ray fluorescence mapping with micro-XANES (X-ray absorption near-edge structure) of entire blots. The identification and quantification of each metal bound to a protein spot has been demonstrated, and the technique has been applied in two exemplary cases. In the first, the speciation of the in vitro binding of exogenous chromium to blood serum proteins was influenced markedly by both the oxidation state of chromium exposed to the serum proteins and the treatment conditions, which is of relevance to the biochemistry of Cr dietary supplements. In the second case, in vivo changes in endogenous metal speciation were examined to probe the influence of oxygen depletion on iron speciation in Shewanella oneidensis.