Effects Of Copper Concentrations Research Articles

Primary Nucleation of Polymorphic α-Synuclein Dimers Depends on Copper Concentrations and Definite Copper-Binding Site.

The primary nucleation process of α-synuclein (AS) that forms toxic oligomeric species is the early stage of the pathological cause of Parkinson's disease. It is well-known that copper influences this primary nucleation process. While significant efforts have been made to solve the structures of polymorphic AS fibrils, the structures of AS oligomers and the copper-bound AS oligomers at the molecular level and the effect of copper concentrations on the primary nucleation are elusive. Here, we propose and demonstrate new molecular mechanism pathways of primary nucleation of AS that are tuned by distinct copper concentrations and by a specific copper-binding site. We present the polymorphic AS dimers bound to different copper-binding sites at the atomic resolution in high- and low-copper concentrations, using extensive molecular dynamics simulations. Our results show the complexity of the primary nucleation pathways that rely on the copper concentrations and the copper binding site. From a broader perspective, our study proposes a new strategy to control the primary nucleation of other toxic amyloid oligomers in other neurodegenerative diseases.

Effect of copper concentrations on microstructure, residual stress and corrosion behavior of Ni100−x-Cux alloy films processed by magnetron co-sputtering

Nickel based alloys have gained importance due to their very good mechanical properties as well as their electrochemical behavior in different environmental conditions. In this regard, thin films of nanocrystalline Ni-Cu alloys have been processed by RF / DC magnetron co-sputtering in Ar gas environment for different copper concentration (10 %, 21 %, 28 % and 39 %). Grain size determination, phase identification and residual stress measurement have been done using an X-ray diffraction technique. A compressive residual stress has been observed and the value of the compressive stress increases with an increase in the Cu concentration in the Ni100−x-Cux alloy films. The electrochemical behavior of thin films of the Ni100−x-Cux alloy has been investigated with the help of potentiodynamic polarization experiments which revealed susceptibility towards pitting corrosion. The rate of corrosion decreases from 0.92 ×10−2 to 0.26 ×10−2 mm / year with the increase in Cu concentration from 10 % to 39 %. The microstructure of thin films of the Ni100−x-Cux alloy has been investigated using a field emission scanning electron microscope (FESEM). The FESEM micrograph shows the formation of pits, and the size of pits decreases with increasing concentration of doped Cu. Experimental results also reveal that the increase in corrosion resistance can correlate with the developing residual stress in the films.

Effect of Copper on Hematological, Biochemical Changes and Reproductive Hormones of the Nile tilapia Oreochromis niloticus

The effect of copper concentrations on alterations in hematological and biochemical parameters as well as reproductive hormones of the Nile tilapia Oreochromis niloticus was investigated. The copper sulfate at sub-chronic concentrations 25, 50 and 75 µg/L on Oreochromis niloticus for 90 days of exposure. Significant changes (P ˂ 0.05) in almost all hematological aspects were found in the all groups exposed to different concentrations of copper 25, 50 and 75 µg/L for 90 days. Biochemical analysis revealed various significant (P ˂ 0.05) differences among the all groups that exposed to 25, 50 and 75 µg/L of copper for 90 days of exposure. There was a significant difference in the copper concentrations in the tissues (P ˂ 0.05) among all treated groups; in liver, gills and kidney. Glucose and cortisol in fish plasma increased significantly, while total protein and total lipids decreased significantly due to copper stress. The obtained results showed also that copper stress was harmful to the fish liver and kidney, where plasma aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, uric acid, and creatinine values were significantly increased with the increasing exposure of copper on Oreochromis niloticus for 90 days compared to the control one. Plasma follicular stimulating hormones (FSH), 17s estradiol (E2) and testosterone (T) were decreased significantly in fish with the increasing exposure of copper concentrations. Among antioxidative enzymes, significant changes were revealed mainly in plasma ceruplasmin and glutathione reductase and glutathione peroxidase activity in liver and gills (P ˂ 0.05. The results demonstrate the deleterious influence of copper on Oreochromis niloticus, even at low doses. So, it is recommended to not use copper too much during treatment of the water that used in growing the fish.

Denitrifying kinetics and nitrous oxide emission under different copper concentrations

Denitrifying activities and nitrous oxide (N2O) emission during denitrification can be affected by copper concentrations. Different denitrifiers were acclimated in sequencing batch reactors with acetate or methanol as the electron donor and nitrate as the electron acceptor. The effect of copper concentrations on the denitrifying activity and N2O emission for the acclimated denitrifiers was examined in batch experiments. Denitrifying activities of the acclimated denitrifiers declined with increasing copper concentrations, and the copper concentration exhibited a higher effect on denitrifiers acclimated with acetate than those acclimated with methanol. Compared with the control without the addition of copper, at the copper concentration of 1 mg/L, the acetate utilization rate reduced by 89% for acetate-acclimated denitrifiers, while the methanol utilization rate only reduced by 15% for methanol-acclimated denitrifiers. Copper also had different effects on N2O emission during denitrification carried out by various types of denitrifiers. For the acetate-acclimated denitrifiers, N2O emission initially increased and then decreased with increasing copper concentrations, while for the methanol-acclimated denitrifiers, N2O emission decreased with increasing copper concentrations.

Population responses of the marine amphipod Corophium volutator (Pallas, 1766) to copper

The effects of copper concentrations on the life-history, growth and reproduction of Corophium volutator were investigated. Amphipods were exposed for 100 days to five sublethal copper concentrations (0.2, 0.4, 0.6, 0.8 and 1 mg l −1). Copper exposure significantly reduced the age-specific survivorship and longevity ( P<0.001). Life-expectancy differed at the various exposure concentrations of copper ( P<0.005). Growth was greatly reduced with copper exposure. The degree of reduction in growth rate increased with increasing metal concentration. Animals exposed to 0.2 mg Cu l −1 exhibited a reduction of 2.4% in the specific growth rate (SGR), while those grown at 0.4, 0.6, and 0.8 mg Cu l −1 exhibited reductions in SGR of 16.7, 23.5 and 20%, respectively. The length of the mature animals was also reduced following copper exposure ( P<0.05). Although sex ratio was not affected ( P=0.225), maturation and fertility were greatly reduced. Survival of ovigerous females and fertility were also affected by copper when mature animals were exposed to these concentrations. These results suggest that long-term exposure of C. volutator to low concentrations of copper could lead to a severe local population density decline because of the reduction of juvenile survivorship and fertility. Long-term exposure of C. volutator to higher concentrations of copper could have more serious consequences such as the local extinction of this species since the juveniles experienced such severe reductions in growth that they were unable to reach mature stage.

Effects of copper concentration on mineral nutrient uptake and copper accumulation in protein of copper-tolerant and nontolerant Lotus purshianus L.

One copper-tolerant and one copper-sensitive inbred line of Lotus purshianus L. derived from a copper mine waste site in Northern California and one inbred line of the same species derived from a pasture next to the mine waste were examined for the effects of excessive copper concentrations on mineral nutrient uptake and accumulation of copper in protein fractions. Plants were grown from seeds for a period of 24 days in a modified Hoagland nutrient solution culture supplemented with 3, 6, and 10 μ M copper as copper sulfate. The basal nutrient solution without copper amendment was used as the control treatment. The uptake of Cu found in the roots was 100 times or more than that in the leaves. The root tissue copper concentrations reached a plateau under 6 μ M copper treatment. The leaf tissue copper concentrations increased with the increase of copper concentration in the solution culture. No difference in pattern of copper uptake was detected between the copper-tolerant and nontolerant plants. The effects of excessive copper concentrations caused reduction of Ca uptake in the leaf tissue and P uptake in both the root and leaf tissues, and no difference was found between the copper-tolerant and nontolerant plants. Increased tissue copper concentration caused greater reduction of Fe, Mn, and Zn uptake in the nontolerant plants than in the tolerant plants; this difference may be important for the growth of the tolerant plants under conditions of excessive copper concentrations. Protein extracted from the roots and leaves of both the copper tolerant and nontolerant plants was subjected to Sephadex G-75 column separation. Two major peaks of protein fractions were detected. Under low (normal level) copper concentration treatment, the copper-tolerant and nontolerant plants had similar Cu/protein ratios. However, under higher copper concentration challenged conditions the copper-tolerant plant had a considerably greater Cu/protein ratio (peak II protein) than the nontolerant plants. The amino acid composition of the copper-rich protein fraction (peak II) extracted from both the tolerant and nontolerant plants demonstrated a high asparate (about 25%) content. The contents of glutamate, cystine, and glycine were about 11, 2.5, and 10%, respectively, and the rest of the amino acids were in a range of 2 to 6%. This pattern of amino acid composition is different from the amino acid composition of the phytochelatin metallothionein-like proteins found in copper-tolerant plants which are very high in cysteine. Instead, the copper rich protein found in the L. purshianus resembles the copper-binding protein found in spinach which has high acidic amino acids and asparate content. More studies are needed to characterize this copper-binding protein and discover its possible role in copper tolerance of L. purshianus.

Observations on the Water Culture Technique for Studying the Effects of Copper Concentrations on Arabica Coffee Seedlings

Observations on the Water Culture Technique for Studying the Effects of Copper Concentrations on Arabica Coffee Seedlings