Arturo Robertazzi

Quantistry

Photosystem II (PSII) is a membrane-bound protein complex that oxidizes water to produce energized protons, which are used to built up a proton gradient across the thylakoidal membrane in the leafs of plants. This light-driven reaction is catalyzed by withdrawing electrons from the Mn4CaO5-cluster (Mn-cluster) in four discrete oxidation steps [S-1...

Photosystem II (PSII) is a membrane-bound protein complex that oxidizes water to produce energized protons, which are used to built up a proton gradient across the thylakoidal membrane in the leafs of plants. This light-driven reaction is catalyzed by withdrawing electrons from the Mn4CaO5-cluster (Mn-cluster) in four discrete oxidation steps [S1 -...

Combination of an electron-rich molecule (e.g. chloride anion or nitrile group) with a chlorinated cyclohexasilane ring produces a supramolecular inverse sandwich complex formed by two guests (Cl(-) or RC≡N) strongly bonded to both faces of a planar host (Si6 ring). In-depth theoretical studies were carried out to investigate the nature of the bon...

The RCSB PDB website has become very popular, with the PDB page being accessed by around 140,000 unique visitors monthly from 140 different countries. The website users are students, educators, science writers, editors and professionals from diverse backgrounds, particularly biologists, specialists in bioinformatics, computational chemistry and man...

Anion-π interactions are attractive interactions between electron-poor aromatic rings and electron rich negative ions or groups. Predicted by theoretical studies in the late 1990s, the first experimental evidence of anion-π interactions was provided by two independent studies in 2004. Since then, the role of these interactions in chemical and in bi...

The supramolecular bonding contacts driving the recognition of chloride ions by macrocyclic imidazolium-based receptors have been investigated by density functional theory calculations, both in vacuo and in solution (DMSO). This computational study reveals that the most stable host−guest complexes in vacuo and solution are different. While the anio...

Extensive quantum chemical DFT calculations were performed on the high-resolution (1.9 Å) crystal structure of photosystem II in order to determine the protonation pattern and the oxidation states of the oxygen-evolving Mn cluster. First, our data suggest that the experimental structure is not in the S(1)-state. Second, a rather complete set of pos...

Multi-core oxomanganese complexes can adopt different oxidation states and protonation patterns depending on ligands and external conditions (for example, solvent, pH, and redox potential). An archetypical example of such complexes is the Mn(4)Ca cluster in the oxygen-evolving complex (OEC) of photosystem II (PSII). Despite the recent high-resoluti...

Over the past 10 years, anion–p interaction has been recognized as an important weak force that may occur between anionic systems and electron-deficient aromatics. Lately, this supramolecular contact has experienced a rapidly growing interest, as reflected by numerous recent literature reports. The present paper highlights the tremendous progress a...

Water plays a pivotal role in the correct functioning of proteins. Hydration is fundamental to their stability and flexibility, to folding process and specific functions, and to protein-protein interactions. In this work, the effects of solvation on proteins dynamics have been investigated by employing molecular dynamics simulations and using myogl...

The one-pot reaction of Mn(OAc)(3) with two equivalents of 6-(pyridine-2-ylhydrazonomethyl)phenol (Hphp) in methanol leads to a unique leuco-verdazyl-type ring. The remarkable cyclodimerization reaction is proposed to involve a number of one-electron oxidative steps mediated by Mn(3+) ions, as well as a very uncommon 1,2-radical aryl migration and...

In the family of respiratory proteins, hemoglobins and myoglobins have been the first to be crystallized in ‘50. Despite the availability of 3D structures, issues regarding the microscopic functioning remain open, such as, for instance, the R to T switching mechanism in hemoglobin or the ligand escape process in myoglobin. Due to the relatively sma...

The crystal lattice of the three isostructural compounds , (C(6)H(8)N(2)H)(2)[M(C(3)H(2)O(4))(2)(H(2)O)(2)].4H(2)O (C(6)H(8)N(2)H = protonated 2-amino-4-picoline, M = Ni/Co/Mn, C(3)H(4)O(4) = malonate dianion; hereafter, malonate) is formed by supramolecular 2D layers. Hydrogen-bonding, pi...pi and lone pair...pi interactions play crucial role in o...

Internal cavities, which are central to the biological functions of myoglobin, are exploited by gaseous ligands (e.g., O(2), NO, CO, etc.) to migrate inside the protein matrix. At present, it is not clear whether the ligand makes its own way inside the protein or instead the internal cavities are an intrinsic feature of myoglobin. To address this i...

Copper-1,10-phenanthroline (phen) complexes Cu(phen)(2)(), Cu(2-Clip-phen), and Cu(3-Clip-phen) (Clip = a serinol bridge between the phen parts) are typically employed as DNA-cleaving agents and are now becoming increasingly important for building multifunctional drugs with improved cytotoxic properties. For instance, Cu(3-Clip-phen) has been combi...

Two compounds, namely, [TTPH(2)](Cl)(2) x 4 H(2)O (1) and [TTPH(2)](Br)(2) x 4 H(2)O (2), (TTP = 4'-p-tolyl-2,2':6',2''-terpyridine) were synthesized from purely aqueous media and characterized by physical techniques. In the solid-state structures of these compounds, interesting supramolecular assemblies are observed. In 1, an unusual staircase-lik...

The binding of the ligand N,N′,N″,N″′-tetrakis{2,4-bis[(dipyridin-2-yl)amino]-1,3,5-triazin-2-yl}-1,4,8,11-tetraazacyclotetradecane (azadendtriz) to four copper(II) ions generates two electron-deficient cavities formed by four coordinated pyridine rings that are capable of hosting electron-rich guests. The molecular structures of [Cu4(azadendtriz)C...

A new hydrogen-bonded dinuclear copper(II) coordination compound has been synthesized from the Schiff-base ligand 6-(pyridine-2-ylhydrazonomethyl)phenol (Hphp). The molecular structure of [Cu(2)(php)(2)(H(2)O)(2)(ClO(4))](ClO(4))(H(2)O) (1), determined by single-crystal X-ray diffraction, reveals the presence of two copper(II) centers held together...

The solid-state structure of an alkaline-earth metal complex reveals the formation of a remarkable supramolecular framework based on concurrent lone pair-pi, pi-pi, and pi-anion interactions whose stability has been investigated by density functional theory.

In the family of respiratory proteins, hemoglobins and myoglobins have been the first to be crystallized in '50. Despite their precise 3D structures are available at high resolution, some questions regarding the microscopic functioning remain yet open. The R to T switching mechanism in hemoglobins and the ligand escape process in myoglobins remain...

Copper complexes of 1,10-phenanthroline (phen) are chemical nucleases employed as footprinting reagents for determining ligand binding sites. The cleavage activity of the parent complex, Cu(phen)2, occurs according to the following mechanism: a) reduction of Cu(phen)22+ to Cu(phen)2+; b) non-coordinative binding of Cu(phen)2+ to DNA; c) Cu(phen)2+...

Cancer is the most common human genetic disease. As the DNA is a crucial target for curing cancer, understanding how molecules bind to nucleic acids and rationalizing the effect of this binding is fundamental to improve the knowledge of anticancer approaches. In recent decades molecular simulations of biological systems have assumed an increasing i...

Mononuclear nickel(II) and copper(II) complexes, namely, (C 6H9N2)2[Ni(ntaH)2] (1), (C5H7N2)2[Cu(mal)2(H 2O)2] (2), and (C5H7N 2)4[Ni(mal)2(H2O) 2](NO3)2 (3) [ntaH3 = nitrilotriacetic acid; C6H8N2H = protonated 2-amino-4-picoline; malH2 = malonic acid; C5H 7N2 = protonated 2-aminopyridine] have been synthesized in water and their crystal structures...

The rational design of a ligand containing two electron-poor pi-rings, i.e. a triazine and a pentafluorophenoxy groups, has allowed the preparation of a copper complex where both the anticipated anion...pi interactions are present.

(ImH)[trans-RuCl(4)(DMSO-S)(Im)], (Im = imidazole, DMSO-S = S-bonded dimethylsulfoxide), NAMI-A, is the first anticancer ruthenium compound that successfully completed Phase I clinical trials. NAMI-A shows a remarkable activity against lung metastases of solid tumors, but is not effective in the reduction of primary cancer. The structurally similar...

Density functional theory calculations have been employed to investigate the role of structural properties of copper phenanthroline complexes for DNA-cleavage activity. Structural changes imposed on the coordination geometries of Cu(phen)(2)(+,2+) (phen = 1,10-phenanthroline) linked by a serinol bridge (abbreviated as Clip) were studied, as well as...

Compounds mimicking the enzyme nitrogenase represent promising alternative routes to the current Haber-Bosch industrial synthesis of ammonia from molecular hydrogen and nitrogen. In this work, we investigated the full catalytic cycle of one of such compounds, Mo-(HIPTN3N) (with HIPT) hexaisopropylterphenyl), by means of DFT calculations. Our result...

QM/MM calculations were employed to investigate the role of hydrogen bonding and pi stacking in several single- and double-stranded cisplatin-DNA structures. Computed geometrical parameters reproduce experimental structures of cisplatin and its complex with guanine-phosphate-guanine. Following QM/MM optimisation, single-point DFT calculations allow...

QM/MM calculations have been employed to investigate the role of hydrogen bonding and pi-stacking in single- and double-stranded DNA oligonucleotides. DFT calculations and Atoms in Molecules analysis on QM/MM-optimized structures allow characterization and estimation of the energies of pi-stacking and hydrogen-bond interactions. This shows that pi-...

The suitability of a hybrid density functional to qualitatively reproduce geometric and energetic details of parallel pi-stacked aromatic complexes is presented. The hybrid functional includes an ad hoc mixture of half the exact (HF) exchange with half of the uniform electron gas exchange, plus Lee, Yang, and Parr's expression for correlation energ...

Density functional calculations and Atoms in Molecules analysis are used to investigate the role of covalent and hydrogen bondings in determining the binding of transition metal complexes to guanine, and the subsequent effect on pairing with cytosine. Hydrogen bonding is ubiquitous, and typically contributes ca. 10% to overall binding, a value that...

Ab initio and density functional calculations are employed to investigate the role of hydrogen bonding in the binding of cisplatin to the purine bases guanine and adenine. Through the use of the theory of atoms in molecules (AIM), it is shown that hydrogen bonds are ubiquitous in such systems, with N-H...N and N-H...Cl interactions present in addit...

Density functional calculations on a range of hydrogen bonded clusters of cisplatin are reported. A systematic search of 1:1 cisplatin:water complexes reveals only three stable minima, which contain a number of common, recurring interactions, such as an N-H...O-H...Cl bridging mode. Expanding these clusters by adding water molecules leads to a mode...