Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 46
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Dalton Trans ; 51(13): 5335, 2022 Mar 29.
Artigo em Inglês | MEDLINE | ID: mdl-35311856

RESUMO

Correction for 'Novel insights into the metal binding ability of ZinT periplasmic protein from Escherichia coli and Salmonella enterica' by Denise Bellotti et al., Dalton Trans., 2020, 49, 9393-9403, DOI: 10.1039/D0DT01626H.

2.
Biomolecules ; 12(1)2022 01 12.
Artigo em Inglês | MEDLINE | ID: mdl-35053269

RESUMO

Zrt2 is a zinc transporter of the ZIP family. It is predicted to be located in the plasma membrane and it is essential for Candida albicans zinc uptake and growth at acidic pH. Zrt2 from C. albicans is composed of 370 amino acids and contains eight putative transmembrane domains and an extra-membrane disordered loop, corresponding to the amino acid sequence 126-215. This protein region contains at least three possible metal binding motifs: HxHxHxxD (144-153), HxxHxxEHxD (181-193) and the Glu- and Asp- rich sequence DDEEEDxE (161-168). The corresponding model peptides, protected at their termini (Ac-GPHTHSHFGD-NH2, Ac-DDEEEDLE-NH2 and Ac-PSHFAHAQEHQDP-NH2), have been investigated in order to elucidate the thermodynamic and coordination properties of their Zn2+ and Cu2+ complexes, with the further aim to identify the most effective metal binding site among the three fragments. Furthermore, we extended the investigation to the peptides Ac-GPHTHAHFGD-NH2 and Ac-PAHFAHAQEHQDP-NH2, where serine residues have been substituted by alanines in order to check if the presence of a serine residue may favor the displacement of amidic protons by Cu2+. In the native Zrt2 protein, the Ac-GPHTHSHFGD-NH2 region of the Zrt2 loop has the highest metal binding affinity, showing that three alternated histidines separated by only one residue (-HxHxH-) bind Zn2+ and Cu2+ more strongly than the region in which three histidines are separated by two and three His residues (-HxxHxxxH- in Ac-PSHFAHAQEHQDP-NH2). All studied Zrt2 loop fragments have lower affinity towards Zn2+ than the zinc(II) binding site on the Zrt1 transporter; also, all three Zrt2 regions bind Zn2+ and Cu2+ with comparable affinity below pH 5 and, therefore, may equally contribute to the metal acquisition under the most acidic conditions in which the Zrt2 transporter is expressed.


Assuntos
Candida albicans , Zinco , Sítios de Ligação , Candida albicans/metabolismo , Proteínas de Transporte/metabolismo , Cobre/química , Histidina/química , Zinco/metabolismo
3.
Inorg Chem ; 60(17): 13332-13347, 2021 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-34414758

RESUMO

Increasing attention has been recently devoted to 89Zr(IV) and 68Ga(III) radionuclides, due to their favorable decay characteristics for positron emission tomography (PET). In the present paper, a deep investigation is presented on Ga(III) and Zr(IV) complexes with a series of tri-(H3L1, H3L3, H3L4 and desferrioxamine E, DFOE) and tetrahydroxamate (H4L2) ligands. Herein, we describe the rational design and synthesis of two cyclic complexing agents (H3L1 and H4L2) bearing three and four hydroxamate chelating groups, respectively. The ligand structures allow us to take advantage of the macrocyclic effect; the H4L2 chelator contains an additional side amino group available for a possible further conjugation with a biomolecule. The thermodynamic stability of Ga(III) and Zr(IV) complexes in solution has been measured using a combination of potentiometric and pH-dependent UV-vis titrations, on the basis of metal-metal competition. The Zr(IV)-H4L2 complex is characterized by one of the highest formation constants reported to date for a tetrahydroxamate zirconium chelate (log ß = 45.9, pZr = 37.0), although the complex-stability increase derived from the introduction of the fourth hydroxamate binding unit is lower than that predicted by theoretical calculations. Solution studies on Ga(III) complexes revealed that H3L1 and H4L2 are stronger chelators in comparison to DFOB. The complex stability obtained with the new ligands is also compared with that previously reported for other hydroxamate ligands. In addition to increasing the library of the thermodynamic stability data of Ga(III) and Zr(IV) complexes, the present work allows new insights into Ga(III) and Zr(IV) coordination chemistry and thermodynamics and broadens the selection of available chelators for 68Ga(III) and 89Zr(IV).

4.
Molecules ; 26(11)2021 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-34071479

RESUMO

Deferoxamine B is an outstanding molecule which has been widely studied in the past decade for its ability to bind iron and many other metal ions. The versatility of this metal chelator makes it suitable for a number of medicinal and analytical applications, from the well-known iron chelation therapy to the most recent use in sensor devices. The three bidentate hydroxamic functional groups of deferoxamine B are the centerpiece of its metal binding ability, which allows the formation of stable complexes with many transition, lanthanoid and actinoid metal ions. In addition to the ferric ion, in fact, more than 20 different metal complexes of deferoxamine b have been characterized in terms of their chemical speciation in solution. In addition, the availability of a terminal amino group, most often not involved in complexation, opens the way to deferoxamine B modification and functionalization. This review aims to collect and summarize the available data concerning the complex-formation equilibria in solutions of deferoxamine B with different metal ions. A general overview of the progress of its applications over the past decade is also discussed, including the treatment of iron overload-associated diseases, its clinical use against cancer and neurodegenerative disorders and its role as a diagnostic tool.


Assuntos
Quelantes/química , Desferroxamina/química , Animais , Antineoplásicos/farmacologia , COVID-19/tratamento farmacológico , Quelantes/farmacologia , Química Farmacêutica/métodos , Eletroquímica/métodos , Eletrólitos , Humanos , Concentração de Íons de Hidrogênio , Íons , Ferro/metabolismo , Quelantes de Ferro/química , Sobrecarga de Ferro/tratamento farmacológico , Cinética , Ligantes , Metais/química , Neoplasias/tratamento farmacológico , Potenciometria , SARS-CoV-2 , Temperatura , Zircônio/química
5.
Curr Med Chem ; 28(35): 7312-7338, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33992060

RESUMO

Some transition metals, like manganese, iron, cobalt, nickel, copper and zinc, required for the biosynthesis of metalloenzymes and metalloproteins, are essential micronutrients for the growth and development of pathogenic microorganisms. Among the defenses put in place by the host organism, the so-called "nutritional immunity" consists of reducing the availability of micronutrients and thus "starving" the pathogen. In the case of metals, microorganisms can fight the nutritional immunity in different ways, i.e. by directly recruiting the metal ion or capturing an extracellular metalloprotein or also through the synthesis of specific metallophores which allow importing the metal in the form of a chelate complex. The best known and most studied metallophores are those directed to iron (siderophores), but analogous chelators are also expressed by microorganisms to capture other metals, such as zinc. An efficient zinc recruitment can also be achieved by means of specialized zinc-binding proteins. A deep knowledge of the properties, structure and action mechanisms of extracytoplasmic zinc chelators can be a powerful tool to find out new therapeutic strategies against the antibiotic and/or antifungal resistance. This review aims to collect the knowledge concerning zincophores (small molecules and proteins in charge of zinc acquisition) expressed by bacterial or fungal microorganisms that are pathogenic for the human body.


Assuntos
Metais , Zinco , Quelantes/farmacologia , Fungos , Humanos , Ferro
6.
J Inorg Biochem ; 214: 111304, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-33197826

RESUMO

Helicobacter pylori is a gram-negative bacterium with gastric localization that can cause many gastrointestinal disorders. Its survival in the host environment strictly requires an efficient regulation of its metal homeostasis, in particular of Ni(II) ions, crucial for the synthesis of some essential enzymes. Hpn is a protein of 60 amino acids, 47% of which are histidines, expressed by H. pylori and avid for nickel, characterized by the presence of an ATCUN (Amino Terminal Cu(II)- and Ni(II)-binding) motif and by two further histidine residues which can act as additional metal anchoring sites. We decided to deepen the following aspects: (i) understanding the role of each histidine in the coordination of metal ions; (ii) comparing the binding affinities for Cu(II), Ni(II) and Zn(II) ions, which are potentially competing metals in vivo; (iii) understanding the Hpn ability of forming ternary and poly-nuclear complexes. For these purposes, we synthesized the Hpn N-terminal "wild-type" sequence (MAHHEEQHG-Am) and the following peptide analogues: MAAHEEQHG-Am, MAHAEEQHG-Am, MAHHEEQAG-Am and MAHAEEQAG-Am. Our results highlight that the histidines in position 4 and 8 lead to the formation of Cu(II) binuclear complexes. The ATCUN motif is by far the most efficient binding site for Cu(II) and Ni(II), while macrochelate Zn(II) complexes are formed thanks to the presence of several suitable anchoring sites (His and Glu). The metal binding affinities follow the order Zn(II) < Ni(II) < < Cu(II). In solutions containing equimolar amount of wild-type ligand, Cu(II) and Ni(II), the major species above pH 5.5 are hetero-binuclear complexes.


Assuntos
Proteínas de Bactérias/química , Helicobacter pylori/química , Metais/química , Histidina/química , Domínios Proteicos
7.
Dalton Trans ; 49(27): 9393-9403, 2020 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-32588863

RESUMO

The ZinT mediated Zn(ii) uptake is one of the major differences in the metabolism of human and bacterial cells that can be challenged when looking for possible highly selective metal-based therapeutics. ZinT is a 216-amino acid periplasmic protein expressed by Gram-negative bacteria, which shuttles Zn(ii) ions to the ZnuABC transporter under zinc-limiting conditions. The suggested metal-binding sites of ZinT correspond to a domain containing three highly conserved histidine residues (His 167, 176 and 178) and to the N-terminal histidine-rich loop HGHHXH (residues 24-29). The coordination chemistry of the ZinT complexes with Zn(ii) and Cu(ii) has been investigated. The present work is focused on the protected peptides Ac-24HGHHSH29-NH2 and Ac-166DHIIAPRKSSHFH178-NH2 as models for the putative metal binding sites of ZinT from Escherichia coli (EcZinT), and Ac-24HGHHAH29-NH2 and Ac-166DHIIAPRKSAHFH178-NH2 from the ZinT protein expressed by Salmonella enterica sv. Typhimurium (SeZinT). The investigated peptides are able to form stable mono-nuclear complexes where the histidine residues represent the principal metal anchoring sites. The ZnuA (a periplasmic component of the ZnuABC transporter) metal binding site exhibits higher affinity for Zn(ii) than ZinT, suggesting that the interaction of the two proteins through the formation of a binary complex may involve the metal transfer from ZinT to ZnuA. In contrast, this would not occur in Cu(ii), since the ZinT complexes are more stable. Furthermore, at acidic pH, where the antimicrobial peptide calcitermin is biologically active, it also binds the metal ions with higher affinity than ZinT, representing a possible efficient competitor and antagonist of ZinT in the host human organism.


Assuntos
Proteínas de Bactérias/química , Cobre/química , Escherichia coli/química , Salmonella enterica/química , Zinco/química , Sítios de Ligação , Concentração de Íons de Hidrogênio
8.
J Inorg Biochem ; 205: 110980, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-31931375

RESUMO

The two branched peptides (AAHAWG)4-PWT2 and (HAWG)4-PWT2 where synthesized by mounting linear peptides on a cyclam-based scaffold (PWT2), provided with four maleimide chains, through a thio-Michael reaction. The purpose of this study was primarily to verify if the two branched ligands had a Cu(II) coordination behavior reproducing that of the single-chain peptides, namely AAHAWG-NH2, which bears an Amino Terminal Cu(II)- and Ni(II)-Binding (ATCUN) Motif, and HAWG-NH2, which presents a His residue as the N-terminal amino acid, in a wide pH range. The study of Cu(II) binding was performed by potentiometric, spectroscopic (UV-vis absorption, CD, fluorescence) and ESI-MS techniques. ATCUN-type ligands ((AAHAWG)4-PWT2 and AAHAWG-NH2) were confirmed to bind one Cu(II) per peptide fragment at both pH 7.4 and pH 9.0, with a [NH2, 2N-, NIm] coordination mode. On the other hand, the ligand HAWG-NH2 forms a [CuL2]2+ species at neutral pH, while, at pH 9, the formation of 1:2 Cu(II):ligand adducts is prevented by amidic nitrogen deprotonation and coordination, to give rise solely to 1:1 species. Conversely, Cu(II) binding to (HAWG)4-PWT2 resulted in the formation of 1:2 copper:peptide chain also at pH 9: hence, through the latter branched peptide we obtained, at alkaline pH, the stabilization of a specific Cu(II) coordination mode which results unachievable using the corresponding single-chain peptide. This behavior could be explained in terms of high local peptide concentration on the basis of the speciation of the Cu(II)/single-chain peptide systems.


Assuntos
Complexos de Coordenação/química , Complexos de Coordenação/síntese química , Cobre/química , Peptídeos/química , Peptídeos/síntese química
9.
Inorg Chem ; 59(1): 274-286, 2020 Jan 06.
Artigo em Inglês | MEDLINE | ID: mdl-31820933

RESUMO

Tau protein is present in significant amounts in neurons, where it contributes to the stabilization of microtubules. Insoluble neurofibrillary tangles of tau are associated with several neurological disorders known as tauopathies, among which is Alzheimer's disease. In neurons, tau binds tubulin through its microtubule binding domain which comprises four imperfect repeats (R1-R4). The histidine residues contained in these fragments are potential binding sites for metal ions and are located close to the regions that drive the formation of amyloid aggregates of tau. In this study, we present a detailed characterization through potentiometric and spectroscopic methods of the binding of copper in both oxidation states to R1 and R3 peptides, which contain one and two histidine residues, respectively. We also evaluate how the redox cycling of copper bound to tau peptides can mediate oxidation that can potentially target exogenous substrates such as neuronal catecholamines. The resulting quinone oxidation products undergo oligomerization and can competitively give post-translational peptide modifications yielding catechol adducts at amino acid residues. The presence of His-His tandem in the R3 peptide strongly influences both the binding of copper and the reactivity of the resulting copper complex. In particular, the presence of the two adjacent histidines makes the copper(I) binding to R3 much stronger than in R1. The copper-R3 complex is also much more active than the copper-R1 complex in promoting oxidative reactions, indicating that the two neighboring histidines activate copper as a catalyst in molecular oxygen activation reactions.


Assuntos
Complexos de Coordenação/química , Cobre/química , Fragmentos de Peptídeos/química , Proteínas tau/química , Sítios de Ligação , Humanos , Conformação Molecular
10.
Metallomics ; 11(12): 1988-1998, 2019 12 11.
Artigo em Inglês | MEDLINE | ID: mdl-31737884

RESUMO

Candida albicans is a widespread human pathogen which can infect humans at different levels. Like the majority of microorganisms, it needs transition metals as micronutrients for its subsistence. In order to acquire these nutrients from the host, C. albicans employs various strategies, also involving chelating proteins specifically expressed to sequester metals from the environment. A histidine-rich protein sequence identified in the C. albicans genome, named C4YJH2, has been recently studied for its putative role in Zn(ii) transport. Two outer membrane major histidine-rich clusters of C4YJH2, namely the domains 131-148 (FHEHGHSHSHGSGGGGGG) and 157-165 (SHSHSHSHS), have been confirmed as strong binding sites for the Cu(ii) and Zn(ii) ions. Nevertheless, the 9-residue "linker" sequence 148-156 (GSDHSGDSK) between the two His-rich fragments of C4YJH2, containing an additional His residue, can also contribute to metal binding. In the present work, the protected peptide Ac-GSDHSGDSK-NH2 and some analogues (Ac-GSDHSGASK-NH2, Ac-GADHAGDAK-NH2, Ac-GSDH-NH2, and Ac-HSGD-NH2) have been synthesized and their metal binding properties have been studied in detail. The thermodynamics of complex-formation equilibria of the above reported ligands with Cu(ii) and Zn(ii) ions have been studied by potentiometry in a wide pH range and the stoichiometry of the formed species has been confirmed by mass spectrometry; the most likely solution structures of the metal complexes are also discussed on the basis of NMR, UV-vis, circular dichroism (CD) and EPR data. The results show the importance of Asp7 in the stabilization of Zn(ii) complexes and suggest a significant role of the (quite abundant) Ser residues in the task of metal uptake and regulation.


Assuntos
Candida albicans/metabolismo , Cobre/metabolismo , Proteínas Fúngicas/metabolismo , Proteínas de Membrana Transportadoras/metabolismo , Fragmentos de Peptídeos/metabolismo , Zinco/metabolismo , Sequência de Aminoácidos , Sítios de Ligação , Candida albicans/química , Candida albicans/fisiologia , Candidíase/metabolismo , Candidíase/microbiologia , Dicroísmo Circular , Cobre/química , Proteínas Fúngicas/química , Humanos , Espectrometria de Massas/métodos , Proteínas de Membrana Transportadoras/química , Fragmentos de Peptídeos/química , Peptídeos/química , Peptídeos/metabolismo , Ligação Proteica , Termodinâmica , Zinco/química
11.
Dalton Trans ; 48(36): 13740-13752, 2019 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-31475275

RESUMO

Calcitermin, an antimicrobial peptide from the fluid of the human airways, is a well-conserved, 15 amino acid C-terminal cleavage fragment of calgranulin C (VAIALKAAHYHTHKE), which is active under acidic pH conditions (pH 5.4). In an attempt to understand the impact of the coordination of Zn(ii) and Cu(ii) on the biological activity of calcitermin, we mutated each of the histidines with an alanine and studied the thermodynamics, binding mode and antimicrobial activity of wild type calcitermin and its H9A, H11A and H13A mutants and their Zn(ii) and Cu(ii) complexes. Both metals strongly enhance the antimicrobial activity of calcitermin-like peptides, although the link between the minimal inhibitory concentration (MIC) values and the stability, charge or structure of the complexes is not so obvious. As expected, the increase in the number of histidines makes the coordination of both metals more effective. There is no preferred Cu(ii) binding site in calcitermin: the stabilities of the Cu(ii)-H9A and Cu(ii)-H13A complexes are almost identical, while the Cu(ii)-H11A complex (in which two histidines are separated by three amino acids and only one His residue is involved in binding) is less stable. On the other hand, the higher stability of the Zn(ii)-H13A complex with respect to those formed by H9A and H11A suggests a pivotal role of His9 and His11 in Zn(ii) complexation. Impressive MIC breakpoints were obtained, similar and lower than those for commonly used antimicrobial agents that treat Candida albicans (Zn(ii) and Cu(ii) complexes of WT calcitermin and H9A, as well as H9A alone), Enterococcus faecalis (H11A, H13A and their metal complexes) and Staphylococcus aureus (H13A and its complexes).


Assuntos
Peptídeos Catiônicos Antimicrobianos/química , Peptídeos Catiônicos Antimicrobianos/farmacologia , Sequência de Aminoácidos , Candida albicans/efeitos dos fármacos , Química Bioinorgânica , Cobre/química , Ligantes , Testes de Sensibilidade Microbiana , Modelos Moleculares , Conformação Proteica , Prótons , Staphylococcus aureus/efeitos dos fármacos , Zinco/química
12.
Curr Med Chem ; 24(8): 818-828, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-27356531

RESUMO

It is well known for several decades that the two enantiomeric forms of a chiral compound can have very different effects on the human body. For this reason the synthesis or extraction from a natural source of a potential new drug, as well as its marketing, require a careful control of its optical purity. Chromatographic techniques can respond extremely well to this need, both in the analytical and in the preparative field. Among the several methods developed for this purpose, one of the first and of the most effective is the Chiral Ligand-Exchange Chromatography, which is based on the stability difference between the metallic diastereomeric complexes containing one or the other of the two enantiomers to be separated and a suitable chiral selector. This method has been effectively used for resolving racemic mixtures of products of biomedical and/or pharmacological interest, such as α - and ß-amino acids either proteinogenic or non-proteinogenic, oligopeptides, amino alcohols or ß-blockers. All these substances are linked together by their ability to bind metal ions, the most widely used of which is Cu(II). The chiral selector can be a component of either the mobile or the stationary phase, to which it can be either chemically bonded or dynamically adsorbed. The latter method has several advantages of convenience and, above all, cheapness. The preparation of dynamically-coated chiral stationary phases for Ligand-Exchange Chromatography has produced a large number of applications, the main of which, both in TLC and in HPLC, are reviewed below.


Assuntos
Cromatografia Líquida/métodos , Preparações Farmacêuticas/análise , Ligantes , Estereoisomerismo
13.
Dalton Trans ; 45(45): 18267-18280, 2016 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-27801457

RESUMO

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.


Assuntos
Cobre/química , Hemoglobinas/química , Níquel/química , Fragmentos de Peptídeos/química , Histidina/metabolismo , Humanos , Concentração de Íons de Hidrogênio , Íons/química , Ligantes , Espectroscopia de Ressonância Magnética , Ligação Proteica , Prótons , Receptor CB1 de Canabinoide/antagonistas & inibidores , Espectrometria de Massas por Ionização por Electrospray
14.
J Inorg Biochem ; 163: 301-310, 2016 10.
Artigo em Inglês | MEDLINE | ID: mdl-27087285

RESUMO

Protein degradation leads to the formation of endogenous peptides, the biological activity of which is most often unknown. The peptide AGHLDDLPGALSAL, recently isolated from mouse brain homogenates, has been recognized as a fragment of the α-chain of hemoglobin. AGHLDDLPGALSAL has the ability of inhibiting the peripheral hyperalgesic inflammatory responses through the indirect activation of the µ-opioid receptors. A peculiarity of AGHLDDLPGALSAL is the presence, at its N-terminus of a strong binding site for divalent transition metal ions, similar to that characterizing the human albumin and called "ATCUN motif". The consequential metal binding ability of AGHLDDLPGALSAL can be connected to its biological activity. For this reason, we decided to investigate the coordination properties of AGHLDDLPGALSAL towards Cu(II), Ni(II) and Zn(II) ions, reported here for the first time. The results confirm that AGHLDDLPGALSAL is a strong ligand for those metals: it can even compete with albumin under suitable conditions. In vitro assays on the inhibition of Cu(II) toxicity towards different cell lines confirmed that the binding ability of AGHLDDLPGALSAL can imply relevant biological consequences.


Assuntos
Albuminas , Hemoglobinas , Peptídeos , Elementos de Transição , Albuminas/química , Albuminas/farmacologia , Hemoglobinas/química , Hemoglobinas/farmacologia , Humanos , Células K562 , Peptídeos/química , Peptídeos/farmacologia , Ligação Proteica , Elementos de Transição/química , Elementos de Transição/farmacologia
15.
Dalton Trans ; 45(13): 5629-39, 2016 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-26923149

RESUMO

Polyhistidine-tags are often used for the affinity purification of polyhistidine-tagged recombinant proteins. These sequences are also found in nature and are often highly conserved across different species. However, their exact role in the biological systems is not clear. The purpose of this work is to shed light on the behavior of poly-His sequences in their interactions with metal ions. This work illustrates the first study of novel poly-(His-Ala) peptides that bind Cu(ii) applying both experimental techniques and extensive computational tools. The studied novel peptides are analogues of the short protected fragment of the pHpG (EDDH9GVG10) peptide, which was found in the venom of Atheris squamigera. Our study presents the properties of metal ion binding-histidine tag complexes and their mutated derivatives. The Cu(ii) binding ability in pHG (Ac-EDDH9G-NH2) is more efficient than in the mutated derivatives, although the number of imidazoles that bind to Cu(ii) ions are similar. Finally, the formation of an α-helical structure is observed in pHG and in one of the mutated derivatives, indicating the importance of the sequence in the poly-(His-Ala) tags.


Assuntos
Cobre/metabolismo , Peptídeos/metabolismo , Sequência de Aminoácidos , Animais , Dicroísmo Circular , Cobre/química , Histidina/genética , Histidina/metabolismo , Concentração de Íons de Hidrogênio , Íons/química , Simulação de Dinâmica Molecular , Mutação , Peptídeos/síntese química , Peptídeos/química , Potenciometria , Ligação Proteica , Venenos de Serpentes/metabolismo , Serpentes/metabolismo , Espectrofotometria Ultravioleta
16.
Dalton Trans ; 45(12): 5151-61, 2016 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-26885710

RESUMO

A protected 30-amino acid fragment, Acetyl-SPDEKHELMIQLQKLDYTVGFCGDGANDCG-Amide, Acetyl-Ser-Pro-Asp-Glu-Lys-His-Glu-Leu-Met-Ile-Gln-Leu-Gln-Lys-Leu-Asp-Tyr-Thr-Val-Gly-Phe-Cys-Gly-Asp-Gly-Ala-Asn-Asp-Cys-Gly-Amide, encompassing the sequence from residues 1164 to 1193 in the encoded protein from Parkinson's disease gene Park9 (YPk9), was studied for manganese and zinc binding. Manganese exposure is considered to be an environmental risk factor connected to PD and PD-like syndrome. Research into the genetic and environmental risk factors involved in disease susceptibility has recently uncovered a link existing between Park9 and manganese. It seems that manganese binding to Park9 (YPk9) protein is involved in the detoxification mechanism exerted by this protein against manganese toxicity. In this study, we used potentiometric, mono- and bi-dimensional (TOCSY, HSQC) NMR, EPR and ESI-MS measurements to analyze complex formation and metal binding sites in the peptide fragment. Presumably octahedral species, in which the Mn(II) ion was bound to oxygens of the carboxyl groups of Glu and Asp, and species where the involvement of sulfur from Cys and nitrogen from His residues, depending on the metal to ligand molar ratio, were detected for manganese coordination. Structural changes in the 30-amino acid fragment were triggered by Zn(II) interaction. A general decrease in the intensity of NMR signals was detected, suggesting the occurrence of chemical exchange among some coordinated species in an intermediate NMR timescale. The coordination may involve both S and N donor atoms from cysteine as well as histidine residues, together with O donor atoms from glutamic and aspartic residues.


Assuntos
Manganês/química , Peptídeos/química , Zinco/química , Complexos de Coordenação/síntese química , Complexos de Coordenação/química , Complexos de Coordenação/metabolismo , Espectroscopia de Ressonância de Spin Eletrônica , Humanos , Concentração de Íons de Hidrogênio , Espectroscopia de Ressonância Magnética , Doença de Parkinson/metabolismo , Doença de Parkinson/patologia , Potenciometria , Ligação Proteica , Espectrometria de Massas por Ionização por Electrospray
17.
Dalton Trans ; 44(7): 3237-50, 2015 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-25597992

RESUMO

The thermodynamic stability of the metallacrown complexes formed by picolinehydroxamic acid (Picha) with Cu(ii), Ni(ii) and Zn(ii) in aqueous solution has been determined by potentiometry, and the speciation models were validated by ESI-MS and UV-visible spectrophotometry. Cu(ii) and Zn(ii) form 12-MC-4 species as the unique metallacrowns present in the solution. While for Cu(ii) the 12-MC-4 is slightly less stable than that obtained with alaninehydroxamic acid (Alaha), the opposite was found for Zn(ii). Moreover, with Cu(ii) unprecedented 15-MC-5 and 18-MC-6 species were identified under ESI-MS conditions. Picha with Ni(ii) forms, in contrast, a 15-MC-5 complex as a unique metallacrown species. Structural studies of the framework of the 12-MC-4 complexes by ab initio methods were also carried out. The results of our investigations allowed us to rationalize not only the different behaviour of Picha in the formation of metallacrowns with the three metal ions, but also the reasons which underpin the strategies for stabilization of these species reported in the literature using ancillary ligands such as pyridine.


Assuntos
Cobre/química , Ácidos Hidroxâmicos/química , Níquel/química , Picolinas/química , Soluções/química , Zinco/química , Cobre/metabolismo , Ácidos Hidroxâmicos/metabolismo , Níquel/metabolismo , Compostos Organometálicos/química , Compostos Organometálicos/metabolismo , Picolinas/metabolismo , Potenciometria/métodos , Soluções/metabolismo , Água/química , Água/metabolismo , Zinco/metabolismo
18.
J Sep Sci ; 38(6): 894-900, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-25560373

RESUMO

Increasing attention has been devoted in the last decades to chiral chromatography, principally to high-performance liquid chromatography techniques using a chiral stationary phase. Many chiral high-performance liquid chromatography columns are commercially available, but, unfortunately, they are most often rather expensive. A cheap alternative to the commercial chiral columns is the dynamic-coating procedure of a standard achiral stationary phase with a chiral selector containing both a chiral domain and a chain or a group able to tightly (but noncovalently) bind the achiral support. This is the case of N(τ) -decyl-l-spinacine, already successfully employed to dynamically cover a reversed-phase column to separate racemic mixtures of amino acids through the ligand-exchange mechanism. In the present work, the same chiral selector is employed to separate racemic mixtures of amino acids and oligopeptides, in the absence of metal ions: no coordination complex is formed, but only electrostatic and weak nonbonding interactions between the chiral phase and the analytes are responsible for the observed enantioselectivity. The new method is simpler than the previous one, very effective in the case of aromatic amino acids and oligopeptides and also suitable for preparative purposes.


Assuntos
Aminoácidos/química , Cromatografia Líquida de Alta Pressão/métodos , Imidazóis/química , Piridinas/química , Aminoácidos/isolamento & purificação , Cromatografia Líquida de Alta Pressão/instrumentação , Troca Iônica , Estereoisomerismo
19.
Dalton Trans ; 43(44): 16680-9, 2014 Nov 28.
Artigo em Inglês | MEDLINE | ID: mdl-25266233

RESUMO

Copper complexes of a poly-His/poly-Gly peptide (EDDHHHHHHHHHGVGGGGGGGGGG-NH2), a natural component of a snake venom, were studied by means of both experimental (thermodynamic, spectroscopic and MS) techniques and molecular dynamics (MD) simulations and density functional theory (DFT) calculations. This peptide proved to be an exceptionally effective copper chelator, forming complexes which are thermodynamically more stable than those formed by both the albumin-like ATCUN motif and several other poly-histidine protein fragments. We show that, in a poly-histidine stretch, copper seems to prefer binding to residues separated by one amino acid and that a correlation between an α-helical structure of the predicted complexes and their thermodynamic stability is observed.


Assuntos
Complexos de Coordenação/química , Cobre/química , Peptídeos/química , Venenos de Víboras/química , Animais , Histidina/química , Simulação de Dinâmica Molecular , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína , Viperidae
20.
Chirality ; 26(6): 313-8, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24771656

RESUMO

The synthesis of Spi(τ-dec), derived from the selective alkylation of L-spinacine (4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridine-6-carboxylic acid) at the τ-nitrogen of its heteroaromatic ring, with a linear hydrocarbon chain of 10 carbon atoms, is described here for the first time. Spi(τ-dec) was successfully employed in the past to prepare home-made chiral columns for chiral ligand-exchange high-performance liquid chromatography. In the present article a new method is described, using Spi(τ-dec) as a chiral selector in high-performance thin-layer chromatography (HPTLC): commercial hydrophobic plates were first coated with Spi(τ-dec) and then treated with copper sulfate. The performance of this new chiral stationary phase was tested against racemic mixtures of aromatic amino acids, after appropriate optimization of both the conditions of preparation of the plates and the mobile phase composition. The enantioselectivity values obtained for the studied compounds were higher than those reported in the literature for similar systems. The method employed here for the preparation of chiral HPTLC plates proved practical, efficient, and inexpensive.


Assuntos
Aminoácidos Aromáticos/química , Aminoácidos Aromáticos/isolamento & purificação , Cromatografia Líquida de Alta Pressão , Cromatografia em Camada Delgada , Cobre/química , Concentração de Íons de Hidrogênio , Indicadores e Reagentes , Solventes , Estereoisomerismo
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...