Norbert Lihi

University of Debrecen · Department of Inorganic and Analytical Chemistry

Antimicrobial peptides are short cationic peptides that are present on biological surfaces susceptible to infection, and they play an important role in innate immunity. These peptides, like other compounds with antimicrobial activity, often have significant superoxide dismutase (SOD) activity. One direction of our research is the characterization o...

As cancer cells exhibit an increased uptake of iron, targeting the interaction with iron has become a straightforward strategy in the fight against cancer. This work comprehensively characterizes the chemical properties of 6-methyl-3-{(2E)-2-[1-(2-pyridinyl)ethylidene]hydrazino}-5H-[1,2,4]triazino[5,6-b]indole (VLX600), a clinically investigated ir...

Superoxide dismutase enzymes (SOD) are pivotal in regulating oxidative stress. In order to model Ni containing SOD enzymes, the results of thermodynamic, spectroscopic and SOD activity studies on the complexes...

In the last 20 years, the research in the field of MRI (magnetic resonance imaging) contrast agents (CA) has been intensified again related to the appearance of a disease called...

Two resins with the hydroxamic acid siderophore desferrioxamine B (DFOB) immobilised as a free ligand or its Fe(iii) complex were prepared to screen the Streptomyces pilosus proteome for proteins involved in siderophore-mediated Fe(iii) uptake. The resin design included a disulfide bond to enable the release of bound proteins under mild reducing co...

The pH-dependent binding strengths and modes of the organometallic [(η6-p-cym)M(H2O)3]2+ (MII = Ru, Os; p-cym = 1-methyl-4-isopropylbenzene) or [(η5-Cp*)M(H2O)3]2+ (MIII = Rh, Ir; Cp* = pentamethylcyclopentadienyl anion) cations towards iminodiacetic acid (H2Ida) and its biorelevant mono- and diphosphonate derivatives N-(phosphonomethyl)-glycine (H...

Malignant melanoma is a major public health problem with an increasing incidence and mortality in the Caucasian population due to its significant metastatic potential. The early detection of this cancer type by imaging techniques like positron emission tomography acts as an important contributor to the long-term survival. Based on literature data,...

The copper(II) complexes of 1,4,7,10-tetraazacyclododecane (cyclen) and 1,4,8,11-tetraazacyclotetradecane (cyclam) were covalently immobilized in mesoporous silica aerogels by the sol-gel method using functionalized silica precursors. The modified macrocyclic precursors are characterized by mass spectrometry (MS) and solution phase nuclear magnetic...

The discovery of the nephrogenic systemic fibrosis (NSF) and its link with the in vivo dissociation of certain Gd(III)-based contrast agents (CAs) applied in the magnetic resonance imaging (MRI) induced a still growing research to replace the compromised agents with safer alternatives. In recent years, several ligands were designed to exploit the l...

The most recently discovered superoxide dismutase enzymes, NiSODs, contain nickel in their active center. This paper surveys the most relevant recent results in this field. Literature data confirm that designated Ni-containing metallopeptides are appropriate mimics of NiSOD. By varying the amino acid sequence of the binding hook, it was unequivocal...

Cysteine containing ligands with free amino- and amidated C-termini were studied and their nickel(II), zinc(II) and cadmium(II) complexes were described in the aspect of their thermodynamic stability and structure, including...

64Cu is considered to be one of the most promising radioisotope in radiotheragnostics (combining therapeutics with diagnostics) because its positron emission is suitable for PET imaging while the combination of...

The copper(II) complex of 1,4,7,10-tetraazacyclododecane [Cu(II)-cyclen] was covalently immobilized in meso-porous silica aerogel. This immobilization significantly alters the catalytic activity of Cu(II)-cyclen when refer-enced to the dissolved complex in the oxidation of phenol by H 2 O 2 in aqueous solution. In order to understand this phenomeno...

Multidisciplinary protein design is reported on a novel metallopeptide mimicking the binding loop of nickel containing SOD enzyme (NiSOD). D-Penicillamine, a natural decomposition product of penicillin, was introduced into the peptide chain yielding the H(Pen)DLPCGLY (wtPen) peptide. The nickel(II) binding ability of wtPen was characterized by ther...

N-oxides of N-heteroaromatic compounds find widespread applications in various fields of chemistry. Although the strictly planar aromatic structure of 1,10-phenanthroline (phen) is expected to induce unique features of the corresponding N-oxides, so far the potential of these compounds has not been explored. In fact, appropriate procedure has not b...

By pursuing the aim of identifying new types of catalysts in the electrolytic production of NaClO3 from NaCl (chlorate process), we report a detailed study on the decomposition of hypochlorous acid accelerated by yttrium(III) chloride (YCl3), yttrium(III) oxide (Y2O3) and telluric acid (Te(OH)6) at 80 °C. The results were compared with those obtain...

We report the Mn(II) complexes with two pyclen-based ligands (pyclen = 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene) functionalized with acetate pendant arms at either positions 3,6 (3,6-PC2A) or 3,9 (3,9-PC2A) of the macrocyclic fragment. The 3,6-PC2A ligand was synthesized in five steps from pyclen oxalate by protecting one of the...

We report the Mn(II) complexes with two pyclen-based ligands (pyclen = 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene) functionalized with acetate pendant arms either at positions 3,6 (3,6-PC2A) or 3,9 (3,9-PC2A) of the macrocyclic fragment. The 3,6-PC2A ligand was synthesized in five steps from pyclen-oxalate by protecting one of the...

Detailed equilibrium, spectroscopic and superoxide dismutase (SOD) activity studies are reported on a nickel complex formed with a new metallopeptide bearing two nickel binding loops of NiSOD. The metallopeptide exhibits unique nickel binding ability and the binuclear complex is a major species with 2×(NH2,Namide,S⁻,S⁻) donor set even in an equimol...

Detailed equilibrium, spectroscopic, and SOD activity studies are reported on nickel(II) complexes formed with the N-terminally free HHDLPCGVY-NH2 (NiSODHH) and HCDLPHGVY-NH2 (NiSODHC) peptides mimicking the nickel binding loop in NiSOD. In these model peptides, cysteine was incorporated in different positions in order to gain better insight into t...

With the aim of identifying new types of water-soluble catalyst precursors for modification of biological membranes by homogeneous hydrogenation in aqueous solution and under mild conditions, we have performed detailed equilibrium and spectroscopic characterization of complex formation between nickel(II) or palladium(II) and salan-type ligands sulf...

The visible region of the electronic absorption spectra of Cu(II) complexes was studied by time-dependent density functional theory (TD-DFT). The performance of twelve functionals in the prediction of absorption maxima (λmax) was tested on eleven compounds with different geometry, donors and charge. The ranking of the functionals for λmax was deter...

Copper(II) complexes of the N‐terminal peptide fragments of tau protein have been studied by potentiometric and various spectroscopic techniques (UV‐vis, CD, ESR and ESI‐MS). The octapeptide Tau(9‐16) (Ac−EVMEDHAG−NH2) contains the H14 residue of the native protein, while Tau(26‐33) (Ac−QGGYTMHQ−NH2) and its mutants Tau(Q26K‐Q33K) (Ac−KGGYTMHK−NH2)...

Equilibrium and detailed spectroscopic characterization of zinc(II) complexes with NiSOD binding loop and its related model fragments are reported in the whole investigated pH-range. The zinc(II) complexes of L1 (HCDLPCGVY-NH2), L2 (Ac-HCDLPCGVY-NH2) and L3 (HCDLACGVY-NH2) and the nickel(II) and zinc(II) complexes of L4 (HCDLPCG-NH2) were studied b...

Detailed equilibrium and spectroscopic characterization of the complex formation processes of the nickel binding loop in NiSOD and its related fragments is reported in the slightly acidic-alkaline pH range. The N-terminally free and protected nonapeptides HCDLPCGVY-NH2 (NiSODM¹), HCDLACGVY-NH2 (NiSODM³), and Ac-HCDLPCGVY-NH2 (NiSODM²) and the N-ter...

Time dependent density functional theory calculations are completed for five Ni(II) complexes formed by polydentate peptides to predict the electronic absorption spectrum. The ligands examined were glycyl‐glycyl‐glycine (GGG), glycyl‐glycyl‐glycyl‐glycine (GGGG), glycyl‐glycyl‐histidine (GGH), glycyl‐glycyl‐cysteine (GGC), and triethylenetetramine...

Correction for ‘Complex formation of nickel( ii ) and zinc( ii ) ions with peptide fragments of rat amylin’ by Ágnes Dávid et al. , New J. Chem. , 2018, DOI: 10.1039/c7nj04605g.

Complex formation equilibria between [(η⁵-Cp*)RhIII(H2O)3]2+ and aminohydroxamic acids (2-amino-N-hydroxyacetamide (α-alahaH), 3-amino-N-hydroxypropanamide (β-alahaH) and 4-amino-N-hydroxybutanamide (GABAha, γ-abhaH)) having the primary amino group in different chelatable position to the hydroxamic function were studied by pH-potentiometric, 1H NMR...

Nickel(II) and zinc(II) complexes of the 19-22 peptide fragments of rat amylin were studied by potentiometric, UV-vis, CD and NMR spectroscopic methods. The results revealed that in contrast with the corresponding copper(II) complexes, the -SSNN- sequence (or 19-22 residues of rat amylin) cannot be a primary anchoring site for nickel(II) and zinc(I...

The N-terminally free but C-terminally amidated peptides Pen-SSACS-NH2 and CSSA-Pen-S-NH2 containing L-penicillamine (Pen) in the sequence have been synthesized and their nickel(II), zinc(II) and cadmium(II) complexes were studied by potentiometric and spectroscopic measurements. This study is the first example for the synthesis and metal complexes...

Complexation of the secondary N-methyl-acetohydroxamic acid (HMeaha) with [(η6-p-cym)Ru(H2O)3]2+, [(η5-Cp*)Rh(H2O)3]2+, [(η6-p-cym)Os(H2O)3]2+ or [(η5-Cp*)Ir(H2O)3]2+ cations and the primary acetohydroxamic acid (HAha) with the former two cations (first time in the literature) has been studied in aqueous solution using pH-potentiometry, NMR, ESI-MS...

Iron(II), iron(III), cobalt(II), zinc(II) cadmium(II) and lead(II) complexes of Asp2 and Asp3 and other Asp/Glu containing ligands were studied by potentiometry. Our goal was to study the influence of β- and γ-carboxylate groups as well as the increased negative charge of the ligands on the complex formation processes. Mainly 1:1 species are presen...

Nickel(II), zinc(II) and cadmium(II) complexes of two hexapeptides ADAAAC-NH2 and AADAAC-NH2 containing terminal amino, separate aspartyl carboxylate and cysteinyl thiolate donor functions have been studied by potentiometric and spectroscopic techniques. For nickel(II), the amino terminus and the aspartyl residues are the primary metal binding site...

Two N-terminally free but C-terminally amidated peptides containing both histidine and cysteine (AAHAAC-NH2 and AHAAAC-NH2) have been synthesized and copper(ii) and palladium(ii) complexes were studied by potentiometry, various spectroscopic methods and DFT calculations. In the case of the copper(ii)-AAHAAC-NH2 system the (NH2, N⁻, N⁻, Nim) coordin...

Iron(III) complexes of three ligands (H2calm, H3anth and H3hyphS) have been studied by means of potentiometric, various spectroscopic (UV-Vis, ¹H-NMR, IR), mass spectrometric, electrochemical and computational (DFT) methods. For investigation of the selectivity of these ligands the studies were completed by characterization of their iron(II)-, copp...

In order to model the metal ion binding capabilities of high molecular mass components of blood the interaction between [(η⁶-p-cym)Ru(H2O)3]²⁺ and terminally protected oligopeptides containing three histidyl moieties (Ac---HHH-NH2, Ac-HAHH-NH2, Ac-HAHAH-NH2 and Ac-H*AH*AH*-NH2, where A = L-alanyl, H = L-histidyl, H* = N3-methyl-L-histidyl) were stu...

Numerous studies have demonstrated the high metal binding capacity and selectivity of peptide molecules. The terminal amino group, deprotonated amide nitrogens, and various side chain donor functions are the most common metal binding sites in these complexes. Imidazole-N donors of histidyl residues are especially important for complex formation bec...

Nickel(ii), zinc(ii) and cadmium(ii) complexes of two N-terminally free hexapeptides AAHAAC and AHAAAC containing separate histidyl and cysteinyl residues have been studied using potentiometric and various spectroscopic (UV-Vis, CD, 1H-NMR) techniques. Both peptides have outstanding metal binding ability but the speciation of the systems and the bi...

Copper(ii) complexes of peptides modelling the sequence of the 17-22 residues of rat amylin have been studied by potentiometric, UV-Vis, CD and ESR spectroscopic methods. The peptides were synthesized in N-terminally free forms, NH2-VRSSNN-NH2, NH2-VRSSAA-NH2, NH2-VRAANN-NH2, NH2-VRSS-NH2, NH2-SSNN-NH2, NH2-SSNA-NH2 and NH2-AANN-NH2, providing a po...

The hexa- and hepta-peptides CSSACS-NH2 and ACSSACS-NH2 have been synthesized by solid phase peptide synthesis and their zinc(II) and cadmium(II) complexes studied by potentiometric, NMR spectroscopic and ESI MS techniques. Both peptides have outstanding zinc(II) and cadmium(II) binding affinity but their coordination chemistry is different. In the...

The systems formed by the V(IV)O(2+) ion with tridentate ligands provided with the (O, Nimine, O) donor set were described. The ligands studied were 2,2'-dihydroxyazobenzene (Hdhab), α-(2-hydroxy-5-methylphenylimino)-o-cresol (Hhmpic), calmagite (H2calm), anthracene chrome red A (H3anth), calcon (H2calc), and calconcarboxylic acid (H3calc(C)). They...