Insights into the Mechanisms of Amyloid Formation of Zn^II-Ab11-28: pH-Dependent Zinc Coordination and Overall Charge as Key Parameters for Kinetics and the Structure of Zn^II-Ab11-28 Aggregates

Self-assembly of amyloidogenic peptides and their metal complexes are of multiple interest including their association with several neurological diseases. Therefore, a better understanding of the role of metal ions in the aggregation process is of broad interest. We report pH-dependent structural and aggregation studies on Zn^II binding to the amyloidogenic peptide Ab11-28. The results suggest that coordination of the N-terminal amine to Zn^II is responsible for the inhibition of amyloid formation and the overall charge for amorphous aggregates

Copper Coordination to Native N‑Terminally Modified versus Full-Length Amyloid-β: Second-Sphere Effects Determine the Species Present at Physiological pH

Alzheimer’s disease is characterized by senile plaques in which metallic ions (copper, zinc, and iron) are colocalized with amyloid-β peptides of different sequences in aggregated forms. In addition to the full-length peptides (Aβ1-40/42), N-terminally truncated Aβ3-40/42 forms and their pyroglutamate counterparts, Aβp3-40/42, have been proposed to play key features in the aggregation process, leading to the senile plaques. Furthermore, they have been shown to be more toxic than the full-length Aβ, which made them central targets for therapeutic approaches. In order to better disentangle the possible role of metallic ions in the aggregation process, copper­(II) coordination to the full-length amyloid peptides has been extensively studied in the last years. However, regarding the N-terminally modified forms at position 3, very little is known. Therefore, copper­(I) and copper­(II) coordination to those peptides have been investigated in the present report using a variety of complementary techniques and as a function of pH. Copper­(I) coordination is not affected by the N-terminal modifications. In contrast, copper­(II) coordination is different from that previously reported for the full-length peptide. In the case of the pyroglutamate form, this is due to preclusion of N-terminal amine binding. In the case of the N-terminally truncated form, alteration in copper­(II) coordination is caused by second-sphere effects that impact the first binding shell and the pH-dependent repartition of the various [Cu­(peptide)] complexes. Such second-sphere effects are anticipated to apply to a variety of metal ions and peptides, and their importance on changing the first binding shell has not been fully recognized yet

DataSheet1_Trace metal fate in soil after application of digestate originating from the anaerobic digestion of non-source-separated organic fraction of municipal solid waste.docx

Introduction: Digestate originating from anaerobic digestion of non-source-separated organic fraction of municipal solid waste (OFMSW) is produced abundantly worldwide and generally discarded in landfills. However, it can be a valuable resource for many bioeconomy strategies as land restoration, only if a consolidated understanding of the contaminants’ presence and behaviour in digestate-amended soil is achieved. This study aimed to investigate the fate of trace metals, namely Zn, Cu, Pb, and Cr found in the digestate, along the soil profile after digestate application on soil, and the influence that other contaminants as pharmaceutical compounds can have on their behaviour in the soil system.Methods: For that, a 90-day soil column experiment was conducted using a fine loamy sand soil topped with a layer of digestate-amended soil. Digestate-amended soil had a soil to digestate proportion of 14 to 1 (dry weight). Two experimental conditions were tested: soil amended with digestate, and soil amended with digestate spiked with the antidiabetic drug metformin. Soil samples were taken at 4 depths on days 1, 7, 21, 35 and 90, and total trace metals concentrations and fractionation were determined via atomic absorption spectroscopy.Results: Results showed that Zn, Cu, Pb ad Cr initially present in the digestate were transferred from the digestate-amended soil layer to the underlying soil layer over time, although in low amounts. Nevertheless, no transfer was detected to the deeper soil layers. Trace metals in soil were predominantly in immobile and less bioavailable forms associated with clay and silicate mineral groups, whereas in the digestate-amended soil they were in more bioavailable forms, which could be related to metals’ migration in the soil layers below. Results also show that the presence of metformin had no influence on trace metal behaviour, giving insight also on possible interactions with other potentially present contaminants as microplastics.Conclusion: The current study showed that OFMSW digestate can be a promising organic nutrient-rich matrix for land restoration even if it may contain high metals’ concentrations because low metal mobility along the soil profile can be expected.</p