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Folic acid (FA) is an essential vitamin involved in crucial metabolic processes, while copper(II) ions play significant roles in various biological functions. This study aims to investigate the interaction between FA and Cu2+ using 1H and 13C NMR spectroscopy under different pH levels and concentrations. The research employed detailed NMR analysis to explore how Cu2+ binds to FA, focusing on changes in chemical shifts, diffusion coefficients, and copper-induced paramagnetic effects. The key findings reveal that Cu2+ predominantly coordinates with the pteridine ring (PTE) of FA, with minimal involvement from the glutamic acid (Glu) moiety. The interaction is strongly concentration-dependent: at lower FA concentrations, Cu2+ binds effectively to the PTE ring, while at higher concentrations, intermolecular interactions among FA molecules hinder copper binding. The study also observed pronounced paramagnetic effects on the PTE and p-aminobenzoic acid protons, with negligible effects on Glu signals. These results provide new insights into the structural characteristics of FA-Cu2+ complexes, contributing to a better understanding of their biochemical interactions and implications for folate metabolism. [ABSTRACT FROM AUTHOR]

Abstract Prion proteins (PrPs) from different species have the enormous ability to anchor copper ions. The N-terminal domain of human prion protein (hPrP) contains four tandem repeats of the –PHGGGWGQ– octapeptide sequence. This octarepeat domain can bind up to four Cu2+ ions. Similarly to hPrP, chicken prion protein (chPrP) is able to interact with Cu2+ through the tandem hexapeptide -HNPGYP- region (residues 53–94). In this work, we focused on the human octapeptide repeat (human Octa 4 , hPrP 60–91) (Ac-PHGGGWGQPHGGGWGQPHGGGWGQPHGGGWGQ-NH 2) and chicken hexapeptide repeat (chicken Hexa 4 , chPrP 54–77) (Ac-HNPGYPHNPGYPHNPGYPHNPGYP-NH 2) prion protein fragments. Due to the fact that PrP is a membrane-anchored glycoprotein and its unstructured and flexible N-terminal domain may interact with the lipid bilayer, our studies were carried out in presence of the surfactant sodium dodecyl sulfate (SDS) mimicking the membrane environment in vitro. The main objective of this work was to understand the effects of copper ion on the structural rearrangements of the human and chicken N-terminal repeat domain. The obtained results provide a fundamental first step in describing the thermodynamic (potentiometric titrations) and structural properties of Cu(II) binding (UV–Vis, NMR, CD spectroscopy) to both human Octa 4 and chicken Hexa 4 repeats in both a DMSO/water and SDS micelle environment. Interestingly, in SDS environment, both ligands indicate different copper coordination modes, which results of the conformational changes in micelle environment. Our results strongly support that copper binding mode strongly depends on the protein backbone structure. Moreover, we focused on previously obtained results for amyloidogenic human and chicken fragments in membrane mimicking environment. Graphical abstract Prion Protein binding to cell membrane occurs via its C-terminal GPI anchor, such that it is reasonable to believe that the presence of lipid bilayers may have an influence on the Cu2+ binding ability of the prion protein octarepeat region. Unlabelled Image Highlights • The human octa repeat prion protein fragment can interact with lipid membrane in vivo. • Sodium dodecyl sulfate micelles (SDS) mimic the membrane environment in vitro. • SDS micelles influence on peptide backbone structure. • The copper binding mode strongly depends on the protein backbone structure. [ABSTRACT FROM AUTHOR]

Recently, we have studied the coordination chemistry of the Cu(II)–histidine-rich C-terminal tail (HRCT) complex of the mycobacterial GroEL1 protein. The structure of this domain differs significantly compared to the well-known methionine-glycine-rich GroEL chaperonin – it was predicted that mycobacterial GroEL1 could play a significant role in the metal homeostasis of Mycobacteria, especially copper. However, we found that this particular domain's pattern also repeats in a number of Ni(II)-binding proteins. Here, we present the studies concerning the properties of GroEL1 HRCT as a ligand for Ni(II) ions. For this purpose, we chose eight model peptides: L1 – Ac-DHDHHHGHAH, L2 – Ac-DKPAKAEDHDHHHGHAH, and 6 mutants of the latter in the pH range of 2–11. We examined the stoichiometry, stability, and spectroscopic features of copper complexes. We noticed that similar to the Cu(II)-complex, the presence of a Lys5 residue significantly increases the stability of the system. The impact of His mutations was also examined and carefully studied using NMR spectroscopy. His9 and His13 are the crucial residues for Ni(II) binding, whereas His12 has minimal relevance in complex formation. [ABSTRACT FROM AUTHOR]

Lycorine (LYC) is an active alkaloid first isolated from Narcissus pseudonarcissus and found in most Amaryllidaceae plants. It belongs to the same family as galantamine, which is the active component of a drug used for the treatment of Alzheimer's disease. Similarly to galantamine, LYC is able to suppress induced amyloid β (Aβ) toxicity in differentiated SH-SY5Y cell lines and it can weakly interact with the N-terminal region of Aβ via electrostatic interactions. The N-terminal Aβ domain is also involved in Cu(II)/Cu(I) binding and the formed complexes are known to play a key role in ROS production. In this study, the Aβ–LYC interaction in the absence and in the presence of copper ions was investigated by using the N-terminal Aβ peptide encompassing the first 16 residues. NMR analysis showed that Aβ can simultaneously interact with Cu(II) and LYC. The Cu(II) binding mode remains unchanged in the presence of LYC, while LYC association is favored when an Aβ–Cu(II) complex is formed. Moreover, UV-VIS studies revealed the ability of LYC to interfere with the catalytic activities of the Aβ–Cu(II) complexes by reducing the ascorbate consumption monitored at 265 nm. [ABSTRACT FROM AUTHOR]

Parkinson's disease (PD) is a severe neurodegenerative disorder affecting movements. After Alzheimer's disease, it is the most common form of neurodegeneration. PD is characterized by the loss of neurons producing dopamine and by the presence of protein aggregates in the brain, known as Lewy bodies. The main constituent of Lewy bodies is the misfolded form of α-synuclein (αSyn), able to form oligomers and fibrils. In addition to protein aggregation, brain damage induced by oxidative stress, is also a frequent phenomenon in PD. αSyn is able to bind Copper ions in both Cu(II) and Cu(I) oxidation states. The metal binding is also maintained when αSyn interacts with membranes. Interestingly, copper binding to αSyn has strong impact either in protein misfolding or in free radical formation, such to provide a link between protein aggregation and oxidative damage. In this review the role of copper and αSyn in PD is discussed with a particular emphasis to elucidate (i) the interaction between copper and αSyn; (ii) the reactivity and (iii) potential toxicity associated with copper-αSyn complexes. [ABSTRACT FROM AUTHOR]

BV02 is a reference inhibitor of 14-3-3 protein–protein interactions, which is currently used as chemical biology tool to understand the role of 14-3-3 proteins in pathological contexts. Due to chemical instability in certain conditions, its bioactive form has remained unclear. Here, we use NMR spectroscopy to prove for the first time the direct interaction between the molecule and 14-3-3σ, and to depict its bioactive form, namely the phthalimide derivative 9 . Our work provides molecular insights to the bioactive form of the 14-3-3 PPI inhibitor and facilitates further development as candidate therapeutic agent. [ABSTRACT FROM AUTHOR]

Prion diseases are neurodegenerative disorders associated with a conformational change of the normal cellular isoform of the prion protein (PrP C ) to an abnormal scrapie isoform (PrP Sc ). human prion protein (hPrP C ) is able to bind up to six Cu(II) ions. Four of them are distributed in the octarepeat domain, containing four tandem-repetitions of the sequence PHGGGWGQ. Immediately outside the octarepeat domain, in so called PrP amyloidogenic region, two additional and independent Cu(II) binding sites, encompassing His96 and His111 residues, respectively, are present. Considering the potential involvement of PrP in cellular redox homeostasis, investigations on Cu(I)–PrP interaction might be also biologically relevant. Interestingly, the amyloidogenic fragment of PrP contains a –M(X) n M– motif, known to act as Cu(I) binding site in different proteins. In order to shed more light on this issue, copper(I) and silver(I) interactions with model peptides derived from that region were analyzed. The results of our studies reveal that both metal ions are anchored to two thioether sulfurs of Met109 and Met112, respectively. Subsequent metal interaction and coordination to His96 and His111 imidazoles are primarily found for Cu(I) at physiological pH. Metal binding was also investigated in the presence of negatively charged micelles formed by the anionic surfactant, sodium dodecyl sulfate (SDS). Our results strongly support that metal binding mode strongly depends on the protein backbone structure. In particular we show that α-helix structuring of the amyloid PrP domain influences both the metal coordination sphere and the binding affinity. [ABSTRACT FROM AUTHOR]

Parkinson’s disease (PD) etiology is closely linked to the aggregation of α-synuclein (αS). Copper(II) ions can bind to αS and may impact its aggregation propensity. As a consequence, deciphering the exact mode of CuII binding to αS is important in the PD context. Several previous reports have shown some discrepancies in the description of the main CuII site in αS, which are resolved here by a new scenario. Three CuII species can be encountered, depending on the pH and the Cu:αS ratio. At low pH, CuII is bound to the N-terminal part of the protein by the N-terminal amine, the adjacent deprotonated amide group of the Asp2 residue, and the carboxylate group from the side chain of the same Asp2. At pH 7.4, the imidazole group of remote His50 occupies the fourth labile equatorial position of the previous site. At high CuII:αS ratio (>1), His50 leaves the coordination sphere of the first Cu site centered at the N-terminus, because a second weak affinity site centered on His50 is now filled with CuII. In this new scheme, the remote His plays the role of a molecular switch and it can be anticipated that the binding of the remote His to the CuII ion can induce different folding of the aS protein, having various aggregation propensity. [ABSTRACT FROM AUTHOR]

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the presence of abnormal α-synuclein (αS) deposits in the brain. Alterations in homeostasis and metal-induced oxidative stress may play a crucial role in the progression of αS amyloid assembly and pathogenesis of PD. Contrary to αS, β-synuclein (βS) is not involved in the PD etiology. However, it has been suggested that the βS/αS ratio is altered in PD, indicating that a correct balance of these two proteins is implicated in the inhibition of αS aggregation. αS and βS share similar abilities to coordinate Cu(II). In this study, we investigated and compared the interaction of Cu(I) with the N-terminal portion of βS and αS by means of NMR, circular dichroism, and X-ray absorption spectroscopies. Our data show the importance of M10K mutation, which induces different Cu(I) chemical environments. Coordination modes 3S1O and 2S2O were identified for βS and αS, respectively. These new insights into the bioinorganic chemistry of copper and synuclein proteins are a basis to understand the molecular mechanism by which βS might inhibit αS aggregation. [ABSTRACT FROM AUTHOR]

Metal ions are fundamental to guarantee the regular physiological activity of the human organism. Similarly, vitamins play a key role in many biological functions of the metabolism, among which are coenzymes, redox mediators, and antioxidants. Due to their importance in the human organism, both metals and vitamins have been extensively studied for their involvement in neurodegenerative diseases (NDs). However, the full potential of the interaction between vitamins and metal ions has not been fully explored by researchers yet, and further investigation on this topic is needed. The aim of this review is to provide an overview of the scientific literature on the implications of vitamins and selected metal ions in two of the most common neurodegenerative diseases, Alzheimer's and Parkinson's disease. Furthermore, vitamin–metal ion interactions are discussed in detail focusing on their bioinorganic chemistry, with the perspective of arousing more interest in this fascinating bioinorganic field. [ABSTRACT FROM AUTHOR]

The Zrt/Irt-like protein (ZIP) family contributes to the metal homeostasis by regulating the transport of divalent metal cations such as Fe2+, Zn2+, Mn2+, Cd2+ and sometimes even Cu2+. Most ZIP members have a long variable loop between transmembrane domains (TMDs) III and IV; this region is predicted to be located in the cytoplasm and is postulated to be the metal ion binding site. In this study, we looked at the thermodynamic behavior and coordination chemistry of Zn2+, Ni2+ and Cu2+ complexes with the histidine-rich domain, Ac-(185)RAHAAHHRHSH(195)-NH2 (HRD), from the yeast TjZNT1 protein, located between TMDs III and IV. The sequence is conserved also in higher species like Thlaspi japonicum. The stability of complexes increases in the series Ni2+ < Zn2+ ≪ Cu2+. The geometry of complexes is very different for each metal and in the case of Zn2+ complexes, high specificity in binding is observed. Moreover, the stability of HRD-Cu2+ complexes was compared with the five His residues containing peptide from Hpn protein (Helicobacter pylori). The results suggest a high ability of HRD in the binding of all three studied metals. [ABSTRACT FROM AUTHOR]

Abstract: Zinc complexes with the extracellular loop of IRT1 (iron-regulated transporter 1), a ZIP (ZRT/IRT — Related Protein) family protein from Arabidopsis thaliana, have been studied. This unstructured fragment is responsible for metal selectivity and is located between the II and III transmembrane domains of IRT1. Zinc complexes with the Ac-(95)MHVLPDSFEMLSSICLEENPWHK(117)-NH2 peptide (IRT1), revealed surprisingly high thermodynamic stability. Additionally, an N-terminal fragment of human/mouse ZIP 13 zinc transporter (MPGCPCPGCGMACPR-NH2, later called ZIP13+C), has been chosen for the thermodynamic stability comparison studies. The relative ZIP13+C stability has been shown using several Zn2+ complexes with artificially arranged multi-cysteine sequences. An interesting coordination mode has been proposed for the IRT1–Zn2+ complex, in which imidazoles from two histidines (His-96 and His-116), a cysteine thiolate (Cys-109) and one of a glutamic acid carboxyl group are involved. All data were collected using potentiometric, NMR and mass spectrometric methods. [Copyright &y& Elsevier]

Abstract: Des-acyl-ghrelin is a 28 amino acid peptide secreted by both human and rat stomach. Together with ghrelin and obestatin, it is obtained by post-translational modification of a 117 aminoacid prepropeptide mainly expressed in distinct endocrine cell type in the stomach. Although its receptor has not been unambiguously identified so far, des-acyl-ghrelin is considered one of the strongest antagonists of ghrelin in activating the growth hormone secretagogue receptor (GHS-R). Here the secondary structure of des-acyl-ghrelin in different experimental conditions has been investigated and compared with that of obestatin, a bioactive peptide having similar biological functions. CD and NMR techniques have been combined for gaining the desired conformational features. The obtained structures support a steady alpha-helix structure spanning residues from 7 to 14, very similar to that observed for obestatin at the same experimental conditions, leading to suggest that a similar secondary structure can be associated with the similar biological role. [Copyright &y& Elsevier]

The aggregation of α-synuclein (αS) is a critical step in the etiology of Parkinson's disease. Metal ions such as copper and iron have been shown to bind αS, enhancing its fibrillation rate in vitro. αS is also susceptible to copper-catalyzed oxidation that involves the reduction of CuII to CuI and the conversion of O2 into reactive oxygen species. The mechanism of the reaction is highly selective and site-specific and involves interactions of the protein with both oxidation states of the copper ion. The reaction can induce oxidative modification of the protein, which generally leads to extensive protein oligomerization and precipitation. CuII binding to αS has been extensively characterized, indicating the N terminus and His-50 as binding donor residues. In this study, we have investigated αS–CuI interaction by means of NMR and circular dichroism analysis on the full-length protein (αS1-140) and on two, designed ad hoc, model peptides: αS1-15 and αS113-130. In order to identify and characterize the metal binding environment in full-length αS, in addition to CuI, we have also used AgI as a probe for CuI binding. Two distinct CuI/AgI binding domains with comparable affinities have been identified. The structural rearrangements induced by the metal ions and the metal coordination spheres of both sites have been extensively characterized. [ABSTRACT FROM AUTHOR]

Abstract: Alzheimer''s disease (AD) is the leading cause of senile dementia. One of the main hallmarks of AD is the presence of amyloid plaques in the brain, primarily formed by fibrils of the amyloid-β (Aβ) peptide. Transition metal ions, such as Cu2+ and Zn2+ have been found at high concentrations in senile plaques isolated from AD patients and evidence have been reached that (i) Aβ aggregation is greatly affected by Cu2+ and Zn2+ and (ii) Cu2+, implicated in the formation of reactive oxygen species, leads to mitochondrial dysfunctions ultimately leading to neuronal cells death. Aβ, apart from being toxic to neural cells, induces reactive astrocytosis in cell culture. Astrocytes play many crucial roles to sustain normal brain function by maintaining the cerebral homeostasis, modulating the synaptic transmission, and providing a metabolic support for neuronal growth. Although many studies have shown that Aβ fibrils interfere in the main astrocytic functions aimed at supporting the neuronal activity, nothing is known about the effects of Zn2+- and Cu2+‐induced Aβ aggregates on astrocyte functions. In this study the effects of treatments with Aβ42, either in absence or in the presence of Cu2+ and Zn2+, on astrocyte cell cultures were evaluated by using classical cellular assay and by looking at changes in metabolic profiles in the cellular medium by using nuclear magnetic resonance spectroscopy (NMR). Our results indicate that metal induced Aβ aggregation strongly affects the metabolites involved in the neurotransmission activity supporting a deleterious impact of Cu2+ and Zn2+ Aβ amyloidogenesis on astrocyte functions. [Copyright &y& Elsevier]

Abstract: Alzheimer''s disease (AD) is a widespread neurodegenerative disease with a very high medical, social and economic burden. The etiopathogenesis of AD is still largely obscure; however, there is growing evidence that aggregation of β-amyloid peptides (Aβ) into a variety of supramolecular structures is critically involved in its insurgence and progression (the so called “amyloid cascade hypothesis”). Recent results point to oligomeric Aβ aggregates rather than mature Aβ fibrils as the major culprit for neurotoxicity; details of the inherent aggregation processes are being progressively clarified. In view of these achievements, early stages of Aβ aggregation are considered today a realistic “druggable” target for the development of new anti-AD agents. Notably, a variety of organic compounds that are able to inhibit effectively Aβ aggregation represent promising drug candidates. Metal based compounds capable of interacting with the N-terminal metal binding site of amyloid peptides might similarly contrast metal-induced Aβ aggregation and serve as potential drugs for AD. In a recent pioneering study Barnham et al. showed that platinum(II) phenanthroline complexes strongly inhibit Aβ oligomerisation and attenuate its neurotoxicity in vitro. A number of additional examples involving metal complexes as inhibitors of Aβ aggregation were reported afterward. On the ground of those results it may be proposed that metal based compounds constitute today a suitable and rich source for novel anti-AD agents. The potential and the limits of this therapeutic option are comprehensively and critically discussed as well as the perspectives for future research. [Copyright &y& Elsevier]

Abstract: The C-terminal region of Escherichia coli SlyD is unstructured and extremely rich in potential metal-binding amino acids, especially in histidine residues. SlyD is able to bind two to seven nickel ions per molecule, in a variety of coordination geometries and coordination numbers. This protein contributes to the insertion of nickel into the hydrogenase precursor protein and it has a peptidyl-prolyl cis/trans-isomerase activity which can be regulated through nickel ions. This inspired us to undertake systematic studies on the coordination ability of two histidine-rich peptides from the C-terminus of the SlyD protein with nickel. Also, it is known that histidine-rich regions are part of a Cu2+ binding domain involved in copper uptake under conditions of metal starvation in vivo in other bacteria. For this reason we decided to examine the complex formation of Ac-AHGHVHGAHDHHHD-NH2 and Ac-GHGHDHGHEHG-NH2 fragments with copper ions, which are also reference metal ions in this study. Experiments were performed in a DMSO/water 30:70 solvent. The Ac-AHGHVHGAHDHHHD-NH2 and Ac-GHGHDHGHEHG-NH2 fragments were synthesized and their interactions with Ni2+ and Cu2+ ions were studied by potentiometric, mass spectrometric, UV–vis, CD, EPR, and NMR spectroscopic techniques in solution. The results show that the Ac-GHGHDHGHEHG-NH2 fragment forms equimolar complexes with both nickel and copper ions. At physiological pH, the metal ion is bound only through nitrogens from imidazole sidechain of histidine residues. On the contrary, Ac-AHGHVHGAHDHHHD-NH2 binds 2 metal ions per molecule, at pH range 5 to 7, even if the 1:2 metal:peptide ratios were used. NMR studies indicate the involvement of all His residues in this pH-range in metal binding of the latter peptide. At higher pH, the stoichiometry changes to 1:1 and the His residues are displaced by amide nitrogens. [Copyright &y& Elsevier]

Abstract: Both human (h) and chicken (Ch) prion proteins (PrP) bind copper ions within the so called “tandem repeat” N-terminal region. Outside this region, hPrP possesses two additional copper binding sites, localized at His-96 and His-111 in the so called “amylodogenic” or neurotoxic region (residues 91–126). Also ChPrP possesses a similar region (ChPrP105−140) containing two His (His-110 and His-124) and an identical hydrophobic tail of 15 amino acids rich in Ala and Gly. The copper binding abilities within such region of ChPrP were investigated by NMR, CD and potentiometry using Ni2+ as diamagnetic probe. The formation of diamagnetic metal complexes allowed to monitor the chemical shift and signal intensity variations and to determine the structural and kinetic features of the His-110 and His-124 metal binding sites. Finally a comparison between the hPrP and ChPrP metal binding abilities was performed. We found that the two prion proteins exhibited different copper and nickel preferences with the favoured metal binding sites localized at opposite His: His-110 for ChPrP, and His-111 for hPrP. [Copyright &y& Elsevier]

Human Prion Protein (hPrPC) is able to bind up to six Cu2+ions. Four of them can be allocated in the “octarepeat domain”, a region of the unstructured N-terminal domain containing four tandem-repetitions of the sequence PHGGGWGQ. It is widely accepted that the additional binding sites correspond to His-96 and His-111 residues. However, recent literature does not agree on the role and the behavior of these sites in Cu2+complexation to hPrPC. In order to shed more light on this topic, some peptidic analogues of the PrP92–113fragment were synthesized: (H96A)PrP92–113, (H111A)PrP92–113, (H96Nτ-Me-His)PrP92–113, (H111Nτ-Me-His)PrP92–113, (H96Nτ-Me-His)PrP92–100, (H111Nτ-Me-His)PrP106–113, where an alanine or a histidine methylated at the τ nitrogen atom of its imidazole ring have been substituted to His-96 or His-111. The first two ligands allowed to confirm that His-111 binding site is stronger than His-96 one: they act as independent sites even at Cu2+-ion substoichiometric levels. Neither multi-histidine binding nor bis-complex formation has been detected at neutral pH. Nτmethylation gave evidence that τ nitrogens of imidazole residues can participate in complex-formation only at acidic pH, where displacement of amidic protons by Cu2+ions is not allowed. Finally, the length of the fragment does not appear to have any significant influence on the behavior of the two His-96 and His-111 binding sites, from the point of view of either the coordination geometry or their relative strength. [ABSTRACT FROM AUTHOR]

The medicinal application of bismuth compounds is focused in two fields: antimicrobial and anticancer. Bi(III) complexes have been used in medicine as an effective treatment of microbial infections, such as peptic ulcers, diarrhoea, gastritis and syphilis. 212Bi and 213Bi are strong α-particle emitters, which, bound to specific ligands, could be promising targeted radio-therapeutic agents for the treatment of cancer. In this work, the coordination of bismuth to three peptides with the Cys-Xaa-Cys motif was studied by potentiometric, spectroscopic, mass spectrometric and NMR methods. We have shown, that sulfur atoms from cysteines are critical donors for the coordination of Bi(III). Our investigation provides insight towards an understanding of the chemistry of bismuth-containing complexes and may lead to the further application of this metal in medicine. [ABSTRACT FROM AUTHOR]

Abstract: Histatins are a family of histidine-rich, cationic peptides up to 38 amino acids long. As other antimicrobial peptides histatins exhibit in vitro activity against both bacteria and yeasts. A 12 amino acid amidated fragment of histatin 5, designated P-113 or demegen, has been identified as the smallest fragment retaining antimicrobial activity comparable to the parent compound. Demegen, AKRHHGYKRKFH, has three His and a N-terminal group known to participate in copper ion coordination. In this study potentiometric and spectroscopic (UV–vis, CD, EPR, NMR) measurements were used to evaluate the stability constants, stoichiometry and structures of Cu2+ complexes with demegen P-113 and its analogues in aqueous solution. The main aim of this work was to understand the role of two adjacent histidine residues in metal ion binding. The comparison with results for modified ligands showed that two histydyl residues are basic for complex formation in the 4.5–7 pH range. [Copyright &y& Elsevier]

The main structural domains of prion proteins, in particular the N-terminal region containing characteristic amino acid repeats, are well conserved among different species, despite divergence in primary sequence. The repeat region seems to play an important role, as verified by pathogenicity only observed in organisms having repeats composed of eight residues. In this work three different peptides belonging to the tandem repeat region of StPrP-2 from the Japanese pufferfish Takifugu rubripes have been considered; the coordination modes and conformations of their complexes with Cu(II) have been investigated by using potentiometric titrations, spectroscopic data, and restrained molecular dynamics simulations. In all cases the histidine imidazole(s) provide the anchoring site for copper, with the further involvement of amide nitrogens depending on the peptide sequence and on pH. An increase in copper binding affinity has been observed going from the shortest peptide, corresponding to a single repeat and containing two histidines, to the longest one, encompassing three repeats with six histidines. [ABSTRACT FROM AUTHOR]

Prion protein (PrP) misfolding is one of the pivotal issues in understanding the rudiments of neurodegenerative disorders. The conformational change of mammalian cellular PrP to scrapie PrP is caused by an unknown agent, but there is reasonable evidence supporting the key role of copper ions in this process. The structure of the avian PrP was found to be very similar to the mammalian protein, although there is only 30% homology in the secondary structure. This work shows that copper ions are very effectively bound by hexarepeat fragments of chicken prion protein, although not as effectively as it was found in the case of mammalian protein. By means of potentiometric and spectroscopic techniques (nuclear magnetic resonance, circular dichroism, UV-vis, and electronic paramagnetic resonance), it was shown that CuII ions coordinate to the chicken PrP hexapeptide domain in physiological pH via imidazole nitrogen donors of His residue(s). The binding pattern changes the structure of peptide involved, indicating a possible impact of CuII ions in the biology and pathology of nonmammalian PrP, which could be similar to that found for mammalian PrP. The present study shows that, similar to the human prion octapeptide repeats, chicken prion hexapeptide repeats might bind copper ions in two different ways, depending on the number of repeats and metal/ligand molar ratio: (i) an intra-repeat coordination mode in which copper ion is chelated by His imidazole and deprotonated amide nitrogen in monomeric peptide and (ii) an inter-repeat coordination mode in which a polymeric peptide ligand (dimer and trimer) forms polyimidazole complexes that are very stable at physiological pH. Two proline residues inserted into the hexapeptide unit have a critical impact on the metal-binding ability. [ABSTRACT FROM AUTHOR]

The reactions of human β-amyloid peptide 1-28 (Aβ28) with AlIII and FeIII ions were investigated by 1H NMR and electrospray ionization mass spectrometry (ESI-MS) under pH conditions close to physiological ones. 1H NMR titrations, performed in the 5.3-8.0 pH range, revealed that no measurable amounts of Aβ28-AlIII or Aβ28-FeIII adducts are formed; such metal adducts could not be obtained even by changing a number of experimental conditions, e.g., temperature, buffer, nature of the salt, etc. These observations were later confirmed by ESI-MS. It is thus demonstrated that Aβ28, at physiological pH, is not able to form binary complexes with AlIII and FeIII ions of sufficient stability to compete with metal hydroxide precipitation. The biological implications of these findings are discussed in the frame of current literature. [ABSTRACT FROM AUTHOR]

The reaction at the ruthenium(ll) complex fac[Ru(CO)3Cl2· (N¹-thz)] (I hereafter; thz = 1,3-thiazole) with human β-amyloid peptide 1-28 (Aβ2e) and the resulting (Ru(CO)3)2+ peptide adduct was investigated by a variety of biophysical methods. ¹H NMFt titrations highlighted a selective interaction ot (Ru(CO)3)2+ with Aβ28 histidine residues; circular dichroism revealed the occurrence of a substantial contormational rearrangement at Mxo; electraspray ionization mass spectrometry (ESI-MS) suggested a prevalent 1:1 metal/peptide stoichiometry and disclosed the nature at peptide-bound metallic fragments. Notably, very similar ESI-MS results were obtained when I was reacted with Aβ42. The implications ot the above tindings tar a possible use at ruthenium compounds in Alzheimer's disease are discussed. [ABSTRACT FROM AUTHOR]

This work focuses on the relationship between the coordination chemistry and antimicrobial activity of Zn (II) and Cu(II) complexes of histatin 5 and the products of its hydrolysis: its N-terminal fragment (histatin 5-8) and C-terminal fragment (histatin 8). Cu(II) coordinates in an albumin-like binding mode and Zn(II) binds to up to 3 His imidazoles. The antimicrobial activity of histatins and their metal complexes (i) strongly depends on pH - they are more active at pH 5.4 than at 7.4; (ii) the complexes and ligands alone are more effective in eradicating Gram-positive bacteria than the Gram-negative ones, and (iii) Zn(II) coordination is able to change the structure of the N-terminal region of histatin 5 (histatin 5-8) and moderately increase all of the studied histatins' antimicrobial potency. [ABSTRACT FROM AUTHOR]

HypB is one of the chaperones required for proper nickel insertion into [NiFe]-hydrogenase. Escherichia coli HypB has two potential Ni(II) and Zn(II) binding sites—the N-terminal one and the so-called GTPase one. The metal-loaded HypB–SlyD metallochaperone complex activates nickel release from the N-terminal HypB site. In this work, we focus on the metal selectivity of the two HypB metal binding sites and show that (i) the N-terminal region binds Zn(II) and Ni(II) ions with higher affinity than the G-domain and (ii) the lower affinity G domain binds Zn(II) more effectively than Ni(II). In addition, the high affinity N-terminal domain, both in water and membrane mimicking SDS solution, has a larger affinity towards Zn(II) than Ni(II), while an opposite situation is observed at basic pH; at pH 7.4, the affinity of this region towards both metals is almost the same. The N-terminal HypB region is also more effective in Ni(II) binding than the previously studied SlyD metal binding regions. Considering that the nickel chaperone SlyD activates the release of nickel and blocks the release of zinc from the N-terminal high-affinity metal site of HypB, we may speculate that such pH-dependent metal affinity might modulate HypB interactions with SlyD, being dependent on both pH and the protein's metal status. [ABSTRACT FROM AUTHOR]

N-Methylation of the peptide amide bond has proven to be a powerful strategy to fine-tune the conformation and properties of peptides. In this context and for the first time, we show that N-methylation can also be used to control the copper(ii) coordination properties of peptides and stabilize at high pH values the copper(ii) species lacking amidate coordination. Namely, we have prepared a derivative of the O-Asp peptide where the copper(ii) coordinating amino acids, i.e. Asp and His residues, were N-methylated (ONMe-Asp). A combined study using potentiometric and spectroscopic (UV-Vis, CD, EPR and NMR) techniques indicates the formation of the wanted major species, [CuH(ONMe-Asp)]2+, where copper(ii) is bound to His4(Nε), His7(Nε), His9(Nε) and Asp2(COO−). With respect to the parent non-methylated O-Asp peptide, [CuH(ONMe-Asp)]2+ is stable at higher pH values but has lower affinity for copper(ii). Additionally, electrochemical studies reveal a Cu(ii) ⇌ Cu(i) redox process with a larger cathodic and anodic peak separation. Species containing copper(ii) coordinating amidates were not observed for this ONMe-Asp peptide. [ABSTRACT FROM AUTHOR]

Oxidative stress results from an imbalance between reactive oxygen species (ROS) production and the body's ability to neutralize them. ROS are reactive molecules generated during cellular metabolism and play a crucial role in normal physiological processes. However, excessive ROS production can lead to oxidative damage, contributing to various diseases and aging. This study is focused on rosmarinic acid (RA), a hydroxycinnamic acid (HCA) derivative well known for its antioxidant activity. In addition, RA has also demonstrated prooxidant behavior under specific conditions involving high concentrations of transition metal ions such as iron and copper, high pH, and the presence of oxygen. In this study, we aim to clarify the underlying mechanisms and factors governing the antioxidant and prooxidant activities of RA, and to compare them with other HCA derivatives. UV–Vis, NMR, and EPR techniques were used to explore copper(II)'s binding ability of RA, caffeic acid, and p-coumaric acid. At the same time, UV–Vis and NMR methods were exploited to evaluate the polyphenols' free radical scavenging abilities towards ROS generated by the ascorbic acid–copper(II) system. All the data indicate that RA is the most effective polyphenol both in copper binding abilities and ROS protection. [ABSTRACT FROM AUTHOR]

The SH-SY5Y neuroblastoma cell line is often used as an in vitro model of neuronal function and is widely applied to study the molecular events leading to Alzheimer's disease (AD). Indeed, recently, basic research on SH-SY5Y cells has provided interesting insights for the discovery of new drugs and biomarkers for improved AD treatment and diagnosis. At the same time, untargeted NMR metabolomics is widely applied to metabolic profile analysis and screening for differential metabolites, to discover new biomarkers. In this paper, a compression technique based on convolutional autoencoders is proposed, which can perform a high dimensionality reduction in the spectral signal (up to more than 300 times), maintaining informative features (guaranteed by a reconstruction error always smaller than 5%). Moreover, before compression, an ad hoc preprocessing method was devised to remedy the scarcity of available data. The compressed spectral data were then used to train some SVM classifiers to distinguish diseased from healthy cells, achieving an accuracy close to 78%, a significantly better performance with respect to using standard PCA-compressed data. [ABSTRACT FROM AUTHOR]

Prion proteins (PrP) from different species have the ability to tightly bind Cu2+ ions. Copper coordination sites are located in the disordered and flexible N-terminal region which contains several His anchoring sites. Among them, two His residues are found in the so called amyloidogenic PrP region which is believed to play a key role in the process leading to oligomer and fibril formation. Both chicken and human amyloidogenic regions have a hydrophobic C-terminal region rich in Ala and Val amino acids. Recent findings revealed that this domain undergoes random coil to α-helix structuring upon interaction with membrane models. This interaction might strongly impact metal binding abilities either in terms of donor sets or affinity. In this study we investigated Cu2+ interaction with an amyloidogenic fragment, chPrP105–140, derived from chicken prion protein (chPrP), in different solution environments. The behavior of the peptide and its metal complexes was analyzed in water and in the presence of negative and positive charged membrane mimicking environments formed by sodium dodecyl sulfate (SDS) and dodecyl trimethyl ammonium chloride (DTAC) micelles. The metal coordination sphere, the metal binding affinity and stoichiometry were evaluated by combining spectroscopic and potentiometric methods. Finally we compare copper(ii) interactions with human and chicken amyloidogenic fragments. Our results indicate that the chicken amyloidogenic fragment is a stronger copper ligand than the human amyloidogenic fragment. [ABSTRACT FROM AUTHOR]

Amyloidogenic proteins are associated with severe neurodegenerative disorders afflicting millions of people worldwide. The main hallmarks of these diseases are the presence of amyloid plaques in the brain, primarily formed by fibrils of misfolded cellular proteins. The process leading to protein aggregation, is far from completely understood. However, it is well accepted that many factors are able to influence the morphology and kinetics of amyloids formation. In the last years, a plethora of studies have suggested that the aggregation process is greatly influenced by the interactions of these proteins with copper and membranes. Amyloidogenic proteins undergo large conformational changes in the presence of membranes and show the presence of stable α helix structures in the presence of high concentrations of unilamellar vesicles or detergent micelles. The regions involved in the helicoidal rearrangements are those which are critical for protein aggregation. In addition, the α helix structuring of amyloidogenic proteins may strongly affect copper binding, in terms of donor atoms and complex stability since metal binding domains are often located near regions experiencing transitions from random-coil to α helix conformations. [ABSTRACT FROM AUTHOR]

α-Synuclein (αSyn) constitutes the main protein component of Lewy bodies, which are the pathologic hallmark in Parkinson's disease. αSyn is unstructured in solution but the interaction of αSyn with lipid membrane modulates its conformation by inducing an α-helical structure of the N-terminal region. In addition, the interaction with metal ions can trigger αSyn conformation upon binding and/or through the metal-promoted generation of reactive oxygen species which lead to a cascade of structural alterations. For these reasons, the ternary interaction between αSyn, copper, and membranes needs to be elucidated in detail. Here, we investigated the structural properties of copper-αSyn binding through NMR, EPR, and XAS analyses, with particular emphasis on copper(I) coordination since the reduced state is particularly relevant for oxygen activation chemistry. The analysis was performed in different membrane model systems, such as micellar sodium dodecyl sulfate (SDS) and unilamellar vesicles, comparing the binding of full-length αSyn and N-terminal peptide fragments. The presence of membrane-like environments induced the formation of a copper:αSyn = 1:2 complex where Cu+ was bound to the Met1 and Met5 residues of two helical peptide chains. In this coordination, Cu+ is stabilized and is unreactive in the presence of O2 in catechol substrate oxidation. [ABSTRACT FROM AUTHOR]

Galantamine is a natural alkaloid extracted from the Amaryllidaceae plants and is used as the active ingredient of a drug approved for the treatment of the early stages of Alzheimer's disease. It mainly acts as an acetylcholinesterase (AChE) inhibitor, increasing concentrations of the acetylcholine neurotransmitter. Recent cellular studies have also shown the ability of galantamine to protect SH-SY5Y cell lines against amyloid-β (Aβ)-induced toxicity. Such investigations have supported and validated further in-depth studies for understanding the chemical and molecular features associated with galantamine-protective abilities. In addition to galantamine, other natural alkaloids are known to possess AChE inhibitory activity; among them lycorine has been extensively investigated for its antibacterial, anti-inflammatory and antitumoral activities as well. Despite its interesting biological properties, lycorine's neuroprotective functions against Aβ-induced damages have not been explored so far. In this research study, the ability of galantamine and lycorine to suppress Aβ-induced in vitro neuronal toxicity was evaluated by investigating the chemical interactions of the two alkaloids with Aβ peptide. A multi-technique spectroscopic analysis and cellular cytotoxicity assays were applied to obtain new insights on these molecular associations. The comparison between the behaviors exhibited by the two alkaloids indicates that both compounds possess analogue abilities to interact with the amyloidogenic peptide and protect cells. [ABSTRACT FROM AUTHOR]

Prion diseases, known as Transmissible Spongiform Encephalopathies (TSEs), are a group of fatal neuronal, and to some extent infectious disorders, associated with a pathogenic protein agent called prion protein (PrP). The human prion protein (hPrP) fragment encompassing the 91–127 region, also known as the amyloidogenic domain, comprises two copper-binding sites corresponding to His-96 and His-111 residues that act as anchors for Cu2+ binding. In this work, we investigated Cu2+ interaction with hPrP91–127 in the presence of the anionic surfactant sodium dodecyl sulfate (SDS), which induces a partial α-helix folding of the peptide. Our data indicate that the Cu2+ coordination ability of the amyloidogenic fragment in the presence of SDS micelles is significantly different to that observed in aqueous solution. This is mainly due to the fact that SDS micelles strongly stabilize the formation of the α-helical structure of the peptide backbone, which is well conserved also upon Cu2+ binding, contrary to the random coil conformation mainly assumed by hPrP91–127 in aqueous solutions. Potentiometric and spectroscopic studies clearly indicate that in the case of SDS containing solutions, Cu2+ ions coordinate simultaneously to both imidazoles, while in the case of water solutions, metal ion coordination involves only a single His side chain, which individually acts as an independent Cu2+ anchoring site. [ABSTRACT FROM AUTHOR]

The heteroaromatic base 5,6-dimethylbenzo-1,3-imidazole (DMBI) proved to be a Brönsted base in an anhydrous ethanol solution, which contained fac , trans -[Ru(CO) 3 Cl 2 ] 2 at 55 °C in air when the DMBI:Ru molar ratio was 2:1. The reaction produced colorless anhydrous single crystals of {(HDMBI) + Cl − }, C 9 H 11 ClN 2 , which were collected and analyzed using X-ray diffraction (XRD) techniques. A network of N–H⋯Cl hydrogen bond type interactions linking the protonated hetero-aromatic base to the chloride anions (bridging bases) stabilizes the crystal and mimics the N–H⋯Cl − interactions that play important roles in CCl channel biological systems. The shortest N⋯Cl contact distance and corresponding N–H⋯Cl angle are 3.073(3) Å and 173(3)°, respectively. The packing is also assisted by weaker C–H⋯Cl − hydrogen bond-type interactions and an extensive network of π⋯π stacking interactions involving HDMBI + cations. Density functional calculations at the B3LYP/6-31G ∗∗ and /6-311++G ∗∗ levels for models of fragments of the crystal structure allowed for the evaluation of geometric parameters, hydrogen bond-type interaction formation energies, and infrared parameters for {(HDMBI) + Cl − } and {(HDMBI) + ⋯Cl − ⋯(HDMBI) + }. [ABSTRACT FROM AUTHOR]

The reaction of [Ru II 2 (CO) 6 Cl 2 ], 1 , in methanol with azoles affords complexes that contain the fa c-{Ru II (CO) 3 } 2+ - core . The complexes presented in this paper have the general formula fac -[Ru II (CO) 3 Cl 2 L], with a molecule L of imidazole (IM), 2 , or N-methyl-imidazole (MIM), 3 , as a ligand in the pseudo -octahedral coordination sphere that is completed by two chlorido ligands cis to each other. The compounds show an appreciable solubility in water (up to ca 1 g/L) at 25 °C, and are well soluble in other solvents, such as alcohol, acetone, dicholoromethane, dimethylsulfoxide, and in mixtures of solvents. In the case where water is present in the medium (10% v/v or higher), significant dissociation of the Ru–N bond that is trans to a carbonyl ligand occurs, and a series of substitutions and other types of reactions may take place afterwards, depending on the reactants and the applied experimental conditions. The synthesis and isolation of single crystals of 2 was performed by reacting the starting dimer 1 with 1-acetylimidazole in alcohol medium. DFT structure simulations/optimizations were carried out at Becke3lyp level of theory by using several basis sets up to 6-311++G ∗∗ for C, H, Cl, N and O atoms, and the Lanl2DZ pseudo -potential for Ru. In vitro cytotoxicity tests for 2 , 3 and fac -[Ru II (CO) 3 Cl 2 (THZ)] (THZ = 1,3-thiazole), 4 , showed IC 50 values mostly in the range 100–200 μM in CH1 (ovarian carcinoma) and SW480 (colon carcinoma) cell lines. ESI-MS studies revealed the ability of these complexes to link the model proteins Lysozyme and Cytochrome c and similar binding patterns are highlighted; interestingly, protein binding is accompanied by a partial release of the original ligands. Fragments of the type [Ru II (CO) 2 ] 2+ or [Ru II (CO)] 2+ are found associated to the proteins. [ABSTRACT FROM AUTHOR]

The coordination modes and thermodynamic stabilities of the complexes of the cysteine-rich N-terminal domain fragment of the ZIP13 zinc transporter (MPGCPCPGCG-NH2) with Zn2+, Cd2+, Bi3+, and Ni2+ have been studied by potentiometric, mass spectrometric, NMR, CD, and UV-vis spectroscopic methods. All of the studied metals had similar binding modes, with the three thiol sulfurs of cysteine residues involved in metal ion coordination. The stability of the complexes formed in solution changes in the series Bi3+ Cd2+ > Zn2+ > Ni2+, the strongest being for bismuth and the weakest for nickel. The N-terminal fragment of the human metalothionein-3 (MDPETCPCP-NH2) and unique histidine- and cysteine-rich domain of the C-terminus of Helicobacter pyroli HspA protein (Ac-ACCHDHKKH-NH2) have been chosen for the comparison studies. It confirmed indirectly which groups were the anchoring ones of ZIP13 domain. Experimental data from all of the used techniques and comparisons allowed us to propose possible coordination modes for all of the studied ZIP13 complexes. [ABSTRACT FROM AUTHOR]

The aggregation of alpha-synuclein (AS) in a critical step in the etiology of parkinson's disease (PD). A central, unresolved question in the pathophysiology of PD relates to the role of AS-metal interaction in amyloid fibril formation and neurodegeneration. Our previous works established a hierarchy in alpha-synuclein-metal ion interactions, where Cu(II) binds specifically to the protein and triggers be aggregation under conditions that might he relevant for the development of PD. Two independent, non-interacting copper-binding sites were identified at the N-terminal region of AS, with significant difference in their affinities for the metal ion. In this work we have solved unknown details related to the structural binding specificity and aggregation enhancement mediated by Cu(II). The high-resolution structural characterization of the highest affinity N-terminus AS-Cu(II) complex is reported here. Through the measurement of AS aggregation kinetics we proved conclusively that the copper-enhanced AS amyloid formation is a direct consequence of the formation of the AS-Cu(II) complex at the highest affinity binding site. The kinetic behavior was not influenced by the His residue at position 50, arguing against an active rate for this residue in the structural and biological events involved is the mechanism of copper-mediated AS aggregation. These new findings are central to elucidate the mechanism through which the metal ion participates in the fibrillization of AS and represent relevant progress in the understanding of the bionorganic chemistry of PD. [ABSTRACT FROM AUTHOR]

The fragment of the zebrafish prion-like protein (PrP-rel-2), encompassing residues 74-86 and unprotected at N-terminus (zf74-86) represents a good model to understand Cu2+and Zn2+binding to ligands containing multi-potential metal donor sites. Zf(74-86) contains four His and His-1 N-terminal amine groups which constitute both copper and zinc anchoring sites. The presence of His at the first position additionally provides the histamine-like binding mode which could compete with the multi-His binding mode. In this study the speciation profiles of the Cu2+and Zn2+complexes with zf74-86 have been obtained. The main species, dominating at physiological pH, have been fully characterized by using different spectroscopic techniques. The detected NMR chemical shift variations and line broadening enhancements, caused by Zn2+and Cu2+respectively, allowed to determine the metal binding sites. Both metal ions showed common binding donor atoms, being 2 or 3 His imidazoles and the N-terminal group involved in Cu2+and Zn2+binding. [ABSTRACT FROM AUTHOR]

Abstract: Laccase, isolated from Cerrena unicolor, is able to transform 3-amino-4-hydroxybenzensulfonic acid into a water soluble phenoxazine dye with an extinction coefficient (ɛ) of 8600M−1 cm−1. The dye has been characterized using a variety of different analytic and spectroscopic techniques like UV–vis spectroscopy, HPLC (High Performance Liquid Chromatography), ESI/MS (Electrospray Ionization Mass Spectrometry) and the following NMR experiments: 1H, 13C, TOCSY (Total Correlation Spectroscopy), HSQC (Heteronuclear Single Quantum Coherence), HMBC (Heteronuclear Multiple Bond Coherence) showing the structure of 2-amino-3-oxo-3H-phenoxazine-8-sulfonic acid. The advantages of the presented biocatalytic system, in alignment with chemical system to obtain Curie_22, are eco-sustainability and one step performance. [Copyright &y& Elsevier]

The article investigates the link between copper homeostasis and copper involvement in different neurological disorders. Copper, which is a redox active metal ion directly involved in oxidation reactions, plays a dual role in producing reactive oxygen species damaging the cells and eliciting antioxidant activity. Copper homeostasis can cause abnormal binding of metal ions resulting to serious disorders such as a neurodegenerative diseases.

Alzheimer's disease (AD) is a neurodegenerative disorder, affecting millions of people worldwide, a number expected to exponentially increase in the future since no effective treatments are available so far. AD is characterized by severe cognitive dysfunctions associated with neuronal loss and connection disruption, mainly occurring in specific brain areas such as the hippocampus, cerebral cortex, and amygdala, compromising memory, language, reasoning, and social behavior. Proteomics and redox proteomics are powerful techniques used to identify altered proteins and pathways in AD, providing relevant insights on cellular pathways altered in the disease and defining novel targets exploitable for drug development. Here, we review the main results achieved by both -omics techniques, focusing on the changes occurring in AD mitochondria under oxidative stress and upon copper exposure. Relevant information arises by the comparative analysis of these results, evidencing alterations of common mitochondrial proteins, metabolic cycles, and cascades. Our analysis leads to three shared mitochondrial proteins, playing key roles in metabolism, ATP generation, oxidative stress, and apoptosis. Their potential as targets for development of innovative AD treatments is thus suggested. Despite the relevant efforts, no effective drugs against AD have been reported so far; nonetheless, various compounds targeting mitochondria have been proposed and investigated, reporting promising results. [ABSTRACT FROM AUTHOR]

14-3-3 are regulatory proteins that through protein–protein interactions (PPI) with numerous binding partners could be involved in several human diseases, including cancer, neurodegenerative disorders, and pathogens infections. Following our research interest in the development of 14-3-3 PPI inhibitors, here we exploited the privileged 4-aminoantipyrine scaffold in the design and synthesis of some derivatives endowed with antiproliferative activity against K-562 cells, and capable of binding to recombinant 14-3-3σ as evidenced by NMR spectroscopy. The binding mode was further explored by molecular modelling, while coupling confocal microscopy with intensitometric analysis showed that compound 1 was able to promote the nuclear translocation of c-Abl at low micromolar concentrations. Overall, 1 is chemically stable compared to parent 14-3-3 PPI inhibitors, and thus emerged as a confirmed hit for further development. [ABSTRACT FROM AUTHOR]

The N-terminal fragment of Aβ (β = beta) peptide is able to bind essential transition metal ions like, copper, zinc and iron. Metal binding usually occurs via the imidazole nitrogens of the three His residues which play a key role in the coordination chemistry. Among all the investigated systems, the interaction between copper and Amyloid β assume a biological relevance because of the interplay between the two copper oxidation states, Cu(II) and Cu(I), and their involvement in redox reactions. Both copper ions share the ability to bind Amyloid β. A huge number of investigations have demonstrated that Cu(II) anchors to the N-terminal amino and His6, His13/14 imidazole groups, while Cu(I) forms a linear complex by coordinating to the His13 and His14 dyad. In this study we have analyzed Cu(I) interaction with the Amyloid β fragment encompassing the first 16 amino-acids. Our data were obtained by means of NMR spectroscopy which provided relevant structural details of the metal complexes. Our findings are consistent with the involvement of two or three His in the Cu(I) coordination sphere and indicate that His6 effectively participates to the metal binding. Cu(I) interaction with the N-terminal fragment of amyloid β. Unlabelled Image • His6, His13 and His14 are the primary Cu(I) binding sites of Aβ (β = beta). • Upon Cu(I) binding, Aβ16 undergoes to specific structural rearrangements. • In the metal complex His6 is close to the His13 His14 dyad. • His6 Nδ, His13 and His14 Nε are the Cu(I) binding donor atoms. • Ag(I) has strong potential in probing Cu(I) interaction with Aβ16. [ABSTRACT FROM AUTHOR]

Plants have evolved a set of mechanisms that control and respond to the uptake and accumulation of both essential and non-essential metals, including chelation and sequestration of these elements by thiol ligands, such as glutathione and phytochelatins. Indeed, such thiol peptides can chelate some metals, quickly form thiol-metal complexes, and segregate them in the vacuolar compartment. Reasonably, conceptually similar mechanisms can be assumed to be responsible for the transport of metal complexes ̶ in particular thiol-cadmium complexes ̶ across the plasma membrane, with the consequent release of this toxic metal in the extracellular environment. Such hypothesis, focusing on prevention and detoxification mechanisms, was here verified in axenically-grown gametophytes of the model liverwort Marchantia polymorpha , exposed to three different cadmium concentrations over five exposure times. From the data obtained, it can be deduced that the cell wall of M. polymorpha moderately reduced the influx of cadmium into the cells, since it was rapidly saturated by this metal. At an intracellular level, cadmium induced the activity, but not the gene expression, of the phytochelatin synthase enzyme, leading to synthesis of phytochelatins. Moreover, both glutathione and phytochelatins chelated cadmium at the cytosolic level and allowed its detoxification, possibly involving tonoplast transporters belonging to type-C ABC subfamily (Mp7g13860 and Mp4g11930). Likewise, cadmium, glutathione and phytochelatins were released extracellularly, thus highlighting a possible novel role in cadmium detoxification, in a pH-dependent manner. The overall results suggest that, in M. polymorpha , glutathione and phytochelatins can accomplish intracellular and extracellular detoxification of cadmium. [Display omitted] • Marchantia polymorpha cell wall only partially counteracts cadmium entry inside the cell. • Cadmium stimulates phytochelatin synthase enzymatic activity, but not its gene expression. • Phytochelatins allow intracellular detoxification of cadmium. • Glutathione and phytochelatins can also be released extracellularly. • Glutathione forms intra- and extracellular complexes with cadmium in a pH-dependent way. [ABSTRACT FROM AUTHOR]

Hemopressin is a neuropeptide, derived from the degradation of the α(1)-chain of hemoglobin, and possesses several pharmacologic properties, such as the ability to block cannabinoid CB1 receptor activity, to cause dose-dependent hypotension and to inhibit food intake. Actually, human hemopressin (PVNFKLLSH) is only the precursor of a class of longer peptides, called “Pepcans”, which bear additional residues at their amino-terminus and possess slightly different chemical and biological properties with respect to hemopressin. The presence of a histidyl residue and the free terminal amine imparts to hemopressin and its derivatives good binding properties towards transition metal ions. In this paper, we present a wide investigation on the complex-formation equilibria of human hemopressin and three analogues towards the Cu(ii) and Ni(ii) ions. The study showed that the main coordination site is always the amino terminus (if not protected), while the C-terminal histidine acts only as an anchoring site for the metal ions at acidic pH, with the formation of a macrochelate complex. The presence of additional residues in N-terminal position produces significant differences in the protonation and complex-formation behaviors of these peptides, which can be explained in terms of charge of the ligand and coordination environment. Although the participation of metal ions in the biological activity of hemopressin and Pepcans has not yet been demonstrated, the data reported here can help to shed light on the mechanisms governing the action of these neuropeptides in vivo. [ABSTRACT FROM AUTHOR]

Highlights: [•] Recent NMR findings on metal interactions with disordered protein domains are discussed. [•] Flexible domains derived either from amyloidogenic proteins or from metal chaperones are considered. [•] The NMR behaviors of different transition metal ions are discussed and compared. [•] The use of NMR to determine (i) the metal coordination sphere, (ii) the structure, (iii) the dynamics and (iv) the binding affinity is discussed. [•] All the benefits and drawbacks of the NMR method are addressed as well. [ABSTRACT FROM AUTHOR]

Transmissible spongiform encephalopathies are associated with the misfolding of the cellular Prion Protein (PrP) to an abnormal protein isoform, called scrapie prion protein (PrP). The structural rearrangement of the fragment of N-terminal domain of the protein spanning residues 91-127 is critical for the observed structural transition. The amyloidogenic domain of the protein encloses two copper-binding sites corresponding to His-96 and His-111 residues that act as anchors for metal ion binding. Previous studies have shown that Cu(II) sequestration by both sites may modulate the peptide's tendency to aggregation as it inflicts the hairpin-like structure that stabilizes the transition states leading to β-sheet formation. On the other hand, since both His sites differ in their ability to Cu(II) sequestration, with His-111 as a preferred binding site, we found it interesting to test the role of Cu(II) coordination to this single site on the structural properties of amyloidogenic domain. The obtained results reveal that copper binding to His-111 site imposes precise backbone bending and weakens the natural tendency of apo peptide to β-sheet formation. [ABSTRACT FROM AUTHOR]