X-Ray Absorption Spectroscopy Measurements of Cu-ProIAPP Complexes at Physiological Concentrations

Abstract

The amyloidogenic islet amyloid polypeptide (IAPP) and the associated pro-peptide ProIAPP1–48 are involved in cell death in type 2 diabetes mellitus. It has been observed that interactions of this peptide with metal ions have an impact on the cytotoxicity of the peptides as well as on their deposition in the form of amyloid fibrils. In particular, Cu(II) seems to inhibit amyloid fibril formation, thus suggesting that Cu homeostasis imbalance may be involved in the pathogenesis of type 2 diabetes mellitus. We performed X-ray Absorption Spectroscopy (XAS) measurements of Cu(II)-ProIAPP complexes under near-physiological (10 μM), equimolar concentrations of Cu(II) and peptide. Such low concentrations were made accessible to XAS measurements owing to the use of the High Energy Resolved Fluorescence Detection XAS facility recently installed at the ESRF beamline BM16 (FAME-UHD). Our preliminary data show that XAS measurements at micromolar concentrations are feasible and confirm that ProIAPP1–48-Cu(II) binding at near-physiological conditions can be detected.

His18 promotes reactive oxidative stress production in copper-ion mediated human islet amyloid polypeptide aggregation

“…Two factors may attribute to this observation, the rst being that Cu(II) directly reacts with the peptide, and the secondly being the only Cu(II) available to convert it to hydroxyl radicals. When H 2 O 2 concentration reached a maximum value aer around 72 h incubation it declined rather rapidly to background level at longer incubation times, similar to the reports by Masad et al 30 We further compared the level of H 2 O 2 generated during the incubation of hIAPP(1-11) and hIAPP (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28) with hIAPP (28)(29)(30)(31)(32)(33)(34)(35)(36)(37) in the presence of 50 mM copper ions. As shown in Fig.…”

“…2a, the 4-line spectrum corresponding to the hydroxyl radical adduct was clearly observed for hIAPP (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28). Remarkably, the intensity of this 4-line spectrum from hIAPP (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28) was greater than that from hIAPP(1-11) and hIAPP (28)(29)(30)(31)(32)(33)(34)(35)(36)(37), agreeing with the above Amplex Red analysis (Fig. 1b).…”

“…All synthetic human and rat IAPP/amylin fragments (hIAPP (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11), hIAPP (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28), hIAPP (28)(29)(30)(31)(32)(33)(34)(35)(36)(37), and rIAPP (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)…”

The Potential of EuPRAXIA@SPARC_LAB for Radiation Based Techniques

“…Soft X-rays as the ones that will be produced by EuPRAXIA@SPARC_LAB are well suited for chemical and biological studies in the water window region. This region includes the K edge of elements such as C, N and O, and the L edge of 3d transition metals, which are of interest in many biologically relevant cases [35,36].…”

High Precision X-Ray Measurements

“…The usage of XAS technique on biological samples is also the main subject of the paper from E. De Santis et al [7], with a particular effort toward the possibility of performing XAS measurements on very diluted samples, with an absorber concentration at the micromolar level. The reported measurements, focused on the Cu(II)-ProIAPP (islet amyloid polypeptide) complexes under near-physiological and equimolar concentrations of Cu(II) and peptide, may have a strong medical impact related to the cell death in type 2 diabetes mellitus, with important consequences on human health.…”