Triggering Cu-coordination change in Cu(ii)-Ala-His-His by external ligands

A switch in copper(ii)-coordination between the two motifs Xxx-Zzz-His (ATCUN) and Xxx-His in the hybride peptide Ala-His-His is induced by adding a ligand such as imidazole.

Trace Element and Heavy Metal Levels in Colorectal Cancer: Comparison Between Cancerous and Non-cancerous Tissues

Cases of colorectal cancer (CRC) have increased dramatically in Middle Eastern and other Asian countries. Many studies indicate an important role of environmental factors, including trace elements as an etiology of cancer. This study aims to assess the concentration of eight trace elements in cancerous and adjacent non-cancerous tissues in case of CRC. In a cross-sectional study, conducted between March 2015 and February 2016, zinc (Zn), chromium (Cr), manganese (Mn), tin (Sn), copper (Cu), aluminum (Al), lead (Pb), and iron (Fe) levels were evaluated among patients suffering from CRC. All the patients underwent a full colonoscopy. Multiple samples were taken from cancerous lesions and adjacent healthy tissues that kept a minimum distance of 10 cm from the lesions. These specimens were kept at -80 °C. The classic flame atomic absorption spectroscopy (FAAS) method was applied in this study. The mean age of the study population was 55.6 ± 12.8. The median of Zn, Cr, Cu, Al, and Pb in cancerous tissues was significantly higher than that of healthy tissues (P < 0.05). Nevertheless, the median of Mn, Sn, and Fe was significantly lower than that of non-cancerous tissues (P < 0.05). Between colon and rectal specimens, we did not find a difference between Cr and Al levels and Zn, Sn, and Cu levels in cancerous and healthy tissues, respectively. We revealed that gender and history of smoking may influence the level of some trace elements. We revealed that the levels of eight elements were significantly different for cancerous and healthy tissues. This may play a role in developing CRC. These findings reflect the importance of environmental pollution in this setting.

New Insight in Copper-Ion Binding to Human Islet Amyloid: The Contribution of Metal-Complex Speciation To Reveal the Polypeptide Toxicity

Type-2 diabetes (T2D) is considered to be a potential threat on a global level. Recently, T2D has been listed as a misfolding disease, such as Alzheimer's and Parkinson's diseases. Human islet amyloid polypeptide (hIAPP) is a molecule cosecreted in pancreatic β cells and represents the main constituent of an aggregated amyloid found in individuals affected by T2D. The trace-element serum level is significantly influenced during the development of diabetes. In particular, the dys-homeostasis of Cu(2+) ions may adversely affect the course of the disease. Conflicting results have been reported on the protective role played by complex species formed by Cu(2+) ions with hIAPP or its peptide fragments in vitro. The histidine (His) residue at position 18 represents the main binding site for the metal ion, but contrasting results have been reported on other residues involved in metal-ion coordination, in particular those toward the N or C terminus. Sequences that encompass regions 17-29 and 14-22 were used to discriminate between the two models of the hIAPP coordination mode. Due to poor solubility in water, poly(ethylene glycol) (PEG) derivatives were synthesized. A peptide fragment that encompasses the 17-29 region of rat amylin (rIAPP) in which the arginine residue at position 18 was substituted by a histidine residue was also obtained to assess that the PEG moiety does not alter the peptide secondary structure. The complex species formed by Cu(2+) ions with Ac-PEG-hIAPP(17-29)-NH2 , Ac-rIAPP(17-29)R18H-NH2 , and Ac-PEG-hIAPP(14-22)-NH2 were studied by using potentiometric titrations coupled with spectroscopic methods (UV/Vis, circular dichroism, and EPR). The combined thermodynamic and spectroscopic approach allowed us to demonstrate that hIAPP is able to bind Cu(2+) ions starting from the His18 imidazole nitrogen atom toward the N-terminus domain. The stability constants of copper(II) complexes with Ac-PEG-hIAPP(14-22)-NH2 were used to simulate the different experimental conditions under which aggregate formation and oxidative stress of hIAPP has been reported. Speciation unveils: 1) the protective role played by increased amounts of Cu(2+) ions on the hIAPP fibrillary aggregation, 2) the effect of adventitious trace amounts of Cu(2+) ions present in phosphate-buffered saline (PBS), and 3) a reducing fluorogenic probe on H2 O2 production attributed to the polypeptide alone.