Interactions between metals and peptides involved in neurodegenerative diseases using CE-ICP/MS : Kd measurements at the nanogram scale
Résumé
Neurodegenerative diseases affect more than 50 million people worldwide and are growing steadily with the aging of the population. The treatments available are not curative but only symptomatic. The literature provides a large evidence for the involvement of transition metals in these diseases, particularly through their interaction with intrinsically disordered proteins, but the precise role of these metals is still uncertain. If the conventional methods (spectrometric studies, potentiometric titrations, calorimetry, ...) already have proven to be the tools of choice to apprehend the metal / ligand complexation and determine with precision the equilibrium constants associated, they are material-consuming. Our objective is therefore to develop a method allowing a fast and economical screening of proteins and peptides. In this context, the coupling between capillary electrophoresis (CE) and inductively coupled plasma - mass spectrometry (ICP/MS) is particularly interesting because of its ability to screen protein / metal complexes from small sample volumes, in the microliter range. We have already shown the interest of this coupling in the study of metalloproteins or proteins with high affinities for metals [1-3]. However, for more labile species, the current method still has to face the problem of dissociation during separation, leading to the distortion of the actual image of a sample. The screening of peptide / metal complexes thus remains an important challenge. To answer this question, we first propose to focus our study on peptides A 1-16 and A 1-42. The peptides have already been successfully separated by capillary electrophoresis [4] and the influence of the metal ions in the aggregation of intrinsically disordered proteins has been thoroughly reviewed in the last years (especially for A 1-42) [5-7]. We will first develop a new CE-ICP/MS based-methodology to determine the constants of affinity of these peptides for copper and zinc. The obtained data will be compared to published data with more classical and validated methods. [1] J. Chamoun, A. Hagège, J. Anal. At. Spectrom., 2005, 20, 1053–1057. [2] T.N.S. Huynh, D. Bourgeois, C. Basset, C. Vidaud, A. Hagège, Electrophoresis, 2015, 36,1374–1382. [3] T. N. S. Huynh, C. Vidaud, A. Hagège, Metallomics, 2016, 8, 1185–1192 [4] R. Verpillot, M. Otto, H. Klafki, M. Taverna, J. Chromatogr. A, 2008, 1214, 157–164. [5] E. Atrián-Blasco, P. Gonzalez, A. Santoro , B. Alies, P. Faller, C. Hureau, Coord. Chem. Rev. 2018, 371, 38–55. [6] P. Faller, C. Hureau, G. La Penna, Acc. Chem. Res. 2014, 47, 2252–2259. [7] J.H. Viles, Coord. Chem. Rev., 2012, 256, 2271–2284.
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