Zn(II) coordination influences the secondary structure, but not antimicrobial activity of the N-terminal histatin 3 hydrolysis product.

The relationship between the coordination chemistry and antimicrobial activity of Zn(II) and Cu(II)-bound histatins, salivary antimicrobial peptides, remains enigmatic. We focus on metal complexes of histatin 3 and its two products of hydrolysis: histatin 4 and its N-terminal fragment (histatin 3-4). The thermodynamic stability of these complexes is quite expected - the binding of Cu(II) the ATCUN motif results in the formation of very stable complexes.

Semenogelins Armed in Zn(II) and Cu(II): May Bioinorganic Chemistry Help Nature to Cope with ?

Proteolytic degradation of semenogelins, the most abundant proteins from human semen, results in the formation of 26- and 29-amino acid peptides (SgIIA and SgI-29, respectively), which share a common 15 amino acid fragment (Sg-15). All three ligands are effective Zn(II) and Cu(II) binders; in solution, a variety of differently metalated species exist in equilibrium, with the [NH, 3N] donor set prevailing at physiological pH in the case of both metals. For the first time, the Cu(II)-induced antimicrobial activity of Sg-15 against is shown.

CH vs. HC-Promiscuous Metal Sponges in Antimicrobial Peptides and Metallophores.

Histidine and cysteine residues, with their imidazole and thiol moieties that deprotonate at approximately physiological pH values, are primary binding sites for Zn(II), Ni(II) and Fe(II) ions and are thus ubiquitous both in peptidic metallophores and in antimicrobial peptides that may use nutritional immunity as a way to limit pathogenicity during infection. We focus on metal complex solution equilibria of model sequences encompassing Cys-His and His-Cys motifs, showing that the position of histidine and cysteine residues in the sequence has a crucial impact on its coordination properties. CH and HC motifs occur as many as 411 times in the antimicrobial peptide database, while similar CC and HH regions are found 348 and 94 times, respectively.

Uracil Derivatives for Halogen-Bonded Cocrystals.

Among non-covalent interactions, halogen bonding is emerging as a new powerful tool for supramolecular self-assembly. Here, along with a green and effective method, we report three new halogen-bonded cocrystals containing uracil derivatives and 1,2,4,5-tetrafluoro-3,6-diiodobenzene as X-bond donor coformer. These multicomponent solids were prepared both by solvent-drop grinding and solution methods and further characterized by powder and single-crystal X-ray diffraction, Fourier-transformed infrared spectroscopy, and thermal methods (TGA-DSC).

Silver(I)-mediated base pairing in DNA involving the artificial nucleobase 7,8-dihydro-8-oxo-1,N-ethenoadenine.

The artificial nucleobase 7,8-dihydro-8-oxo-1,N-ethenoadenine (X) was investigated with respect to its ability to engage in Ag(I)-mediated base pairing in DNA. Spectroscopic data indicate the formation of dinuclear X-Ag(I)-X homo base pairs and mononuclear X-Ag(I)-C base pairs (C, cytosine). Density functional theory calculations and molecular dynamics simulations indicate that the nucleobase changes from its lactam tautomeric form prior to the formation of the Ag(I)-mediated base pair to the lactim form after the incorporation of the Ag(I) ions.

Deciphering the H-Bonding Preference on Nucleoside Molecular Recognition through Model Copper(II) Compounds.

The synthetic nucleoside acyclovir is considered an outstanding model of the natural nucleoside guanosine. With the purpose of deepening on the influence and nature of non-covalent interactions regarding molecular recognition patterns, three novel Cu(II) complexes, involving acyclovir (acv) and the ligand receptor N-(2-hydroxyethyl)ethylenediamine (hen), have been synthesized and thoroughly characterized. The three novel compounds introduce none, one or two acyclovir molecules, respectively.

Adipato bridged novel hexanuclear Cu(ii) and polymeric Co(ii) coordination compounds involving cooperative supramolecular assemblies and encapsulated guest water clusters in a square grid host: antiproliferative evaluation and theoretical studies.

Two new coordination compounds involving hexanuclear Cu(ii), viz., [Cu6(phen)6(μ4-adpt)4(H2O)2](NO3)4·10H2O (1) and polymeric Co(ii), viz., {[(μ2-adpt)4Co(μ2-H2O)2Co(H2O)4]·4H2O}n (2) (phen = 1,10-phenanthroline; adpt = adipate) have been synthesized and characterized using elemental analysis, TGA, spectroscopic (IR, electronic and ESR), PXRD and single crystal X-ray diffraction techniques.

Synthesis, X-ray characterization and regium bonding interactions of a trichlorido(1-hexylcytosine)gold(iii) complex.

Herein we report the synthesis and X-ray characterization of a gold(iii) complex of 1-hexylcytosine via N(3). The AuClN complexes stack on top of each other by reciprocal [AuCl] regium bonding interactions. After the first example 35 years ago, this is the second available structure of a cytosine nucleobase model complexed to gold(iii).

Synthesis, reactivity, X-ray characterization and docking studies of N/N-(2-pyrimidyl)-adenine derivatives.

The reaction of adenine with 2-chloropyrimidine yields as a major product the unexpected N-(2-pyrimidyl)-adenine (1) and as a minor one N-(2-pyrimidyl)-adenine (2). Both compounds have been characterized by X-ray diffraction analysis. Moreover, we report the formation of a 1:1 co-crystal (3) composed by compound (1) and adenine that was formed serendipitously during the synthesis of (1).

Probing the effect of N-alkylation on the molecular recognition abilities of the major groove N7-binding site of purine ligands.

The study of the metal binding pattern of N-methyladenines (1-, 3-, 7- or 9-Meade) towards Cu-iminodiacetate-like chelates is addressed on the basis of XRD crystal structures of sixteen novel ternary compounds. Except for three compounds, all others feature an square-based Cu(II) coordination, type 4 + 1, and the efficient cooperation of a CuN7 bond with an intra-molecular N6-H⋯O(coord. carboxylate) interligand interaction as the major metal-binding pattern.

The Role of Lead(II) in Nucleic Acids.

Although lead(II) is naturally not associated with nucleic acids, this metal ions has been applied with DNA and RNA in various contexts. Pb2+ is an excellent hydrolytic metal ion for nucleic acids, which is why it is mainly used as probing agent for secondary structure and to determine metal ion binding sites both in vitro and in vivo. A further application of lead(II) is in structural studies, i.

X-ray Crystal Structure of a Metalled Double-Helix Generated by Infinite and Consecutive C*-Ag -C* (C*:N -Hexylcytosine) Base Pairs through Argentophilic and Hydrogen Bond Interactions.

The synthesis of a metalled double-helix containing exclusively silver-mediated C*-C* base pairs is reported herein (C*=N hexylcytosine). Remarkably, it is the first crystal structure containing infinite and consecutive C*-Ag -C* base pairs that form a double helix. The Ag ion occupies the center between two C* residues with N(3)-Ag bond lengths of 2.

Triple-bridged ferromagnetic nickel(II) complexes: a combined experimental and theoretical DFT study on stabilization and magnetic coupling.

Two dinuclear [Ni2L2(o-(NO2)C6H4COO)2(H2O)] (1), [Ni2L2(p-(NO2)C6H4COO)2(H2O)]·0.5CH3OH (2) complexes and one trinuclear [Ni3L2(p-(NO2)C6H4COO)4]·C2H5OH (3) Ni(II) complex have been synthesized using a tridentate Schiff base ligand, 1-[(3-dimethylamino-propylimino)-methyl]-naphthalen-2-ol (HL) along with ortho- and para-nitro benzoate as co-ligands. All these three (1-3) complexes have been characterized by spectral analysis, X-ray crystallography and variable temperature magnetic susceptibility measurements.

Crystal structures and DFT calculations of new chlorido-dimethylsulfoxide-M(III) (M = Ir, Ru, Rh) complexes with the N-pyrazolyl pyrimidine donor ligand: kinetic vs. thermodynamic isomers.

New chlorido-dimethylsulfoxide-iridium(III), ruthenium(III) and rhodium(III) complexes with the 2-(1H-pyrazol-1-yl)-pyrimidine (pyrapyr) ligand (OC-6-N1)-[Rh(III)Cl3(DMSO-κS)(pyrapyr)] (1a, N = 3 and 1b, N = 4); (OC-6-N1)-[Ru(III)Cl3(DMSO-κS)(pyrapyr)] (2a, N = 3 and 2b, N = 4) and (OC-6-N1)-[Ir(III)Cl3(DMSO-κS)(pyrapyr)] (3a, N = 3 and 3b, N = 4) have been synthesized and characterized by spectroscopic techniques and by single crystal X-ray diffraction studies (1a, 1b, 2a, 2b, a disordered crystal 3a/3b and a cocrystal 3a·3b). In all cases, the metal centers show octahedral geometry coordinated to three chloride ligands and one S coordinated dimethylsulfoxide (DMSO-κS). The coordination sphere of the metal is completed by the pyrapyr molecule.

Use of metalloligands [CuL] (H2L = salen type di-Schiff bases) in the formation of heterobimetallic copper(II)-uranyl complexes: photophysical investigations, structural variations, and theoretical calculations.

Five heterobimetallic copper(II)-uranium(VI) complexes [(CuL(1))UO2(NO3)2] (1), [{CuL(1)(CH3CN)}UO2(NO3)2] (2), [{CuL(1)(CH3COCH3)}UO2(NO3)2] (3), [{CuL(2)(CH3CN)}UO2(NO3)2](4), and [{CuL(2)(CH3COCH3)}UO2(NO3)2][{CuL(2)}UO2(NO3)2] (5) have been synthesized by reacting the Cu(II)-derived metalloligands [CuL(1)] and [CuL(2)] (where, H2L(1) = N,N'-bis(α-methylsalicylidene)-1,3-propanediamine and H2L(2) = N,N'-bis(salicylidene)-1,3-propanediamine) with UO2(NO3)2·6H2O in 1:1 ratio by varying the reaction temperature and solvents. Absorption and fluorescence quenching experiments (steady-state and time-resolved) indicate the formation of 1:1 ground-state charge transfer copper(II)-uranium(VI) complexes in solution. X-ray single-crystal structure reveals that each complex contains diphenoxido bridged Cu(II)-U(VI) dinuclear core with two chelated nitrato coligands.

Metallomacrocycles as anion receptors: combining hydrogen bonding and ion pair based hosts formed from Ag(I) salts and flexible bis- and tris-pyrimidine ligands.

Two self-assembled hosts are formed from Ag(I) salts and bis-pyrimidyl ligands and X-ray characterized. Both are able to incorporate two anions into the structure combining hydrogen bonding and electrostatic interactions.

Experimental and theoretical studies on the coordination chemistry of the N1-hexyl substituted pyrimidines (uracil, 5-fluorouracil and cytosine).

N(1)-Hexyl substituted pyrimidines were shown to present solubility properties closer to the real bases than the commonly used methyl and ethyl derivatives, yielding bi-layered structures in the solid state. The study of their coordination capabilities, mainly with Ag(I) and Hg(II), is presented in order to prove their reactivity. A series of coordination complexes, namely, [Hg(N(1)-hexyl-5-fluorouracilate)2]4·6H2O (1), (Ag(+))·[Ag(N(1)-hexyl-5-fluorouracilate)2](-) (2), [Ag(NO3)(N(1)-hexyluracil-κO(4))4] (3), [ZnBr2(N(1)-hexylcytosine)2] (4), [CdBr2(N(1)-hexylcytosine)2] (5), [HgBr2(N(1)-hexylcytosine)2] (6) and [CoBr2(N(1)-hexylcytosine)2] (7), have been synthesized in good yields and X-ray characterized.

RNAs' uracil quartet model with a non-essential metal ion.

We have recently communicated the resemblance of 1-hexyluracil in the crystal state with a lipid bilayer (CrystEngComm, 2010, 12, 362-365). Treatment of this molecule with silver nitrate yields a model, using a non-essential metal ion, of a uracil quartet with geometric parameters comparable to those previously found in RNA strands.

Intermolecular C-H...pi interactions in 1,5-diphenyl-3-(2-pyridyl)-2-pyrazoline.

The title compound, C(20)H(17)N(3), is a derivative of 1,3,5-triaryl-2-pyrazoline and can act as an N,N'-bidentate ligand. This molecule features strong fluorescence that can be explained by an extended pyridyl-C=N-N-phenyl system. The three-dimensional structure is formed by means of an extended network of weak C-H.

Di-μ-chlorido-bis-{chlorido[(R)/(S)-1,5-di-phenyl-3-(2-pyridyl-κN)-2-pyrazoline-κN]zinc(II)}.

In the centrosymmetric binuclear title compound, [Zn(2)Cl(4)(C(20)H(17)N(3))(2)], the coordination geometry of the Zn(II) ion can be described as a distorted ZnN(2)Cl(3) trigonal bipyramid (τ = 0.89), arising from the N,N'-bidentate ligand, a terminal chloride ion and two bridging chloride ions. The N atoms occupy one axial and one equatorial site and the terminal chloride ion occupies an equatorial site.

Anion-pi interactions in bisadenine derivatives: a combined crystallographic and theoretical study.

In this manuscript we report a high-level ab initio study of anion-pi interactions involving N9-methyl-adenine, N6-methyl-adenine, N9-methyl-hypoxanthine, a dimer of N9-methyl-adenine, and N9,N9'-trimethylene-bisadenine. DNA bases like adenine are electron-deficient arenes that are well suited for interacting favorably with anions. We demonstrate that these compounds are able to interact favorably with anions.