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The bond distance is the simplest and most obvious indicator of the nature of a given chemical bond. However, for rare chemistry, it may happen that it is not yet firmly established. In this communication, we will show that the formally-triple protactinium(V) mono-oxo bond is predicted to be longer than what was previously reported in the solid state and in solution, based on robust quantum mechanical calculations, supported by an extensive methodological study. Furthermore, additional calculations are used to demonstrate that the Pa-O oxo bond of interest is more sensitive to complexation than the supposedly analogous U-O yl ones, not only in terms of bond distance but also of finer bond descriptors associated with the effective bond multiplicity.

Polonium (Po, Z = 84) is a main-block element with poorly known physico-chemical properties. Not much information has been firmly acquired since its discovery by Marie and Pierre Curie in 1898, especially regarding its speciation in aqueous solution and spectroscopy. In this work, we revisit the absorption properties of two complexes, [PoCl 5 ] - and [PoCl 6 ] 2- , using quantum mechanical calculations. These complexes have the potential to exhibit a maximum absorption at 418 nm in HCl medium (for concentrations of 0.5 mol L -1 and above). Initially, we examine the electronic spectra of the Po 4+ free ion and of its isoelectronic analogue, Bi 3+ , in the spin-orbit configuration interaction (SOCI) framework. Our findings demonstrate that the SOCI matrix should be dressed with correlated electronic energies and that the quality of the spectra is largely improved by decontracting the reference states at the complete active space plus singles (CAS + S) level. Subsequently, we investigate the absorption properties of the [PoCl 5 ] - and [PoCl 6 ] 2- complexes in two stages. Firstly, we perform methodological tests at the MP2/def2-TZVP gas phase geometries, indicating that the decontraction of the reference states can be skipped without compromising the accuracy significantly. Secondly, we study the solution absorption properties by means of single-point calculations performed at the solvated geometries, obtained by an implicit solvation treatment or a combination of implicit and explicit solvation. Our results highlight the importance of saturating the first coordination sphere of the Po IV ion to obtain a qualitatively correct picture. Finally, we conclude that the known-for-decades 418 nm peak could be attributed to a mixture of both the [PoCl 5 (H 2 O)] - and [PoCl 6 ] 2- complexes. This finding not only aligns with the behaviour of the analogous Bi III ion under similar conditions but also potentially provides an explanation for previous discrepancies in the literature.

Protactinium ( Z = 91) is a very rare actinide with peculiar physico-chemical properties. Indeed, although one may naively think that it behaves similarly to either thorium or uranium by its position in the periodic table, it may in fact follow its own rules. Because of the quite small energy gap between its valence shells (in particular the 5f and 6d ones) and also the strong influence of relativistic effects on its properties, it is actually a challenging element for theoretical chemists. In this article, we combine experimental information, chemical arguments and standard first-principle calculations, complemented by implicit and explicit solvation, to revisit the stepwise complexation of aqueous protactinium(V) with sulfate and oxalate dianionic ligands (SO 4 2- and C 2 O 4 2- , respectively). From a methodological viewpoint, we notably conclude that it is necessary to at least saturate the coordination sphere of protactinium(V) to reach converged equilibrium constant values. Furthermore, in the case of single complexations ( i.e. with one sulfate or oxalate ligand bound in the bidentate fashion), we show that it is necessary to maintain the coordination of one hydroxyl group, present in the supposed [PaO(OH)] 2+ precursor, to obtain coherent complexation constants. Therefore, we predict that this hydroxyl group is maintained in the formation of 1 : 1 complexes while we confirm that it is withdrawn when coordinating three sulfate or oxalate ligands. Finally, we stress that this work is a first step toward the future use of theoretical predictions to elucidate the enigmatic chemistry of protactinium in solution.

Uranium trioxide, UO 3 , has a T-shaped structure with bent uranyl, UO 2 2+ , coordinated by an equatorial oxo, O 2- . The structure of cation UO 3 + is similar but with an equatorial oxyl, O •- . Neutral and cationic uranium trioxide coordinated by nitrates were characterized by collision induced dissociation (CID), infrared multiple-photon dissociation (IRMPD) spectroscopy, and density functional theory. CID of uranyl nitrate, [UO 2 (NO 3 ) 3 ] - (complex A1 ), eliminates NO 2 to produce nitrate-coordinated UO 3 + , [UO 2 (O • )(NO 3 ) 2 ] - ( B1 ), which ejects NO 3 to yield UO 3 in [UO 2 (O)(NO 3 )] - ( C1 ). Finally, C1 associates with H 2 O to afford uranyl hydroxide in [UO 2 (OH) 2 (NO 3 )] - ( D1 ). IRMPD of B1 , C1 , and D1 confirms uranyl equatorially coordinated by nitrate(s) along with the following ligands: ( B1 ) radical oxyl O •- ; ( C1 ) oxo O 2- ; and ( D1 ) two hydroxyls, OH - . As the nitrates are bidentate, the equatorial coordination is six in A1 , five in B1 , four in D1 , and three in C1 . Ligand congestion in low-coordinate C1 suggests orbital-directed bonding. Hydrolysis of the equatorial oxo in C1 epitomizes the inverse trans influence in UO 3 , which is uranyl with inert axial oxos and a reactive equatorial oxo. The uranyl ν 3 IR frequencies indicate the following donor ordering: O 2- [best donor] ≫ O •- > OH - > NO 3 - .

One of the most important properties influencing the chemical behavior of an element is the electron affinity (EA). Among the remaining elements with unknown EA is astatine, where one of its isotopes, 211 At, is remarkably well suited for targeted radionuclide therapy of cancer. With the At - anion being involved in many aspects of current astatine labeling protocols, the knowledge of the electron affinity of this element is of prime importance. Here we report the measured value of the EA of astatine to be 2.41578(7) eV. This result is compared to state-of-the-art relativistic quantum mechanical calculations that incorporate both the Breit and the quantum electrodynamics (QED) corrections and the electron-electron correlation effects on the highest level that can be currently achieved for many-electron systems. The developed technique of laser-photodetachment spectroscopy of radioisotopes opens the path for future EA measurements of other radioelements such as polonium, and eventually super-heavy elements.

Location-based routing protocols for vehicular ad hoc networks (VANETs) use location information to determine routing decisions. This information is provided by a location service that is queried by nodes in order to properly forward packets to communication partners. This paper presents the semiflooding location service, a proactive flooding-based location service that drastically reduces the number of update packets sent over the network compared to traditional flooding-based location services. This goal is achieved by each node partially forwarding location information. We present both deterministic and probabilistic approaches for this algorithm, which remains very simple. A mathematical model is proposed to show the effectiveness of this solution. The cases of homogeneous 1D, 2D, and 3D networks were studied for both deterministic and probabilistic forwarding decisions. We compare our algorithm with simple flooding and with the multipoint-relay (MPR) flooding of the optimized-link-state-routing (OLSR) protocol, and we show that our algorithm, despite being very simple, has excellent scalability properties. The mean number of generated messages ranges with the mean number of the neighbors of one random network node.

Purpose: Numerous studies demonstrated that prosthetic overhang and over-sizing cause pain and stiffness following total knee arthroplasty (TKA), but none considered volume changes within the joint capsule. This study was designed to investigate differences in volumes of resected bone compared to implanted components in TKA, and to determine the incidence and factors related to 'over-voluming'., Methods: Three-dimensional reconstructions were created from 100 magnetic resonance imaging scans taken to design patient-specific instruments for TKA. The preoperative simulations were used to calculate the volume ratio (VR) by dividing volume of planned components by that of planned bone resections. Uni- and multi-variable linear regressions were performed to determine associations between 'over-voluming' (VR > 1.0) and gender, implant size and version (standard versus narrow), osteophytes, resection levels, external rotation of the femoral component, hip-knee-ankle (HKA) angle, mechanical lateral distal femoral angle (mLDFA), and mechanical medial proximal tibial angle (mMPTA)., Results: The overall implant/bone volume ratio was 0.91 ± 0.11 (range 0.63-1.16) with 'over-voluming' observed in 24 knees. Multi-variable regression confirmed over-voluming to be associated with lower mLDFA (OR 0.66; CI 0.45-0.93; p = 0.026) and extensive osteophytes (OR 0.14; CI 0.03-0.61; p = 0.014), but not HKA angle (OR 0.98; CI 0.76-1.26; p = n.s.)., Conclusions: Over-voluming was observed in 24% of knees, in which the implant volume exceeded the resected volume by up to 16%. Over-voluming was associated with intra-articular femoral valgus (low mLDFA), but not directly associated with tibial deformity (mMPTA) or HKA angle. Over-voluming could be associated with prosthetic overhang or excessive tensions within the joint capsule, and, therefore, contribute to unexplained pain and stiffness following TKA., Level of Evidence: IV, Retrospective cohort study.

A central goal of chemistry is to achieve ultimate oxidation states, including in gas-phase complexes with no condensed phase perturbations. In the case of the actinide elements, the highest established oxidation states are labile Pu(VII) and somewhat more stable Np(VII). We have synthesized and characterized gas-phase AnO 3 (NO 3 ) 2 - complexes for An = U, Np, and Pu by endothermic NO 2 elimination from AnO 2 (NO 3 ) 3 - . It was previously demonstrated that the PuO 3 + core of PuO 3 (NO 3 ) 2 - has a Pu-O • radical bond such that the oxidation state is Pu(VI); it follows that in UO 3 (NO 3 ) 2 - it is the stable U(VI) oxidation state. On the basis of the relatively more facile synthesis of NpO 3 (NO 3 ) 2 - , a Np(VII) oxidation state is inferred. This interpretation is substantiated by reactivity of the three complexes: NO 2 spontaneously adds to UO 3 (NO 3 ) 2 - and PuO 3 (NO 3 ) 2 - but not to NpO 3 (NO 3 ) 2 - . This unreactive character is attributed to a Np(VII)O 3 + core with three stable Np═O bonds, this in contrast to reactive U-O • and Pu-O • radical bonds. The computed structures and reaction energies for the three AnO 3 (NO 3 ) 2 - support the conclusion that the oxidation states are U(VI), Np(VII), and Pu(VI). The results establish the extreme Np(VII) oxidation state in a gas-phase complex, and demonstrate the inherently greater stability of Np(VII) versus Pu(VII).

Gas-phase plutonium nitrate anion complexes were produced by electrospray ionization (ESI) of a plutonium nitrate solution. The ESI mass spectrum included species with all four of the common oxidation states of plutonium: Pu(III), Pu(IV), Pu(V), and Pu(VI). Plutonium nitrate complexes were isolated in a quadrupole ion trap and subjected to collision-induced dissociation (CID). CID of complexes of the general formula PuOx(NO3)y(-) resulted in the elimination of NO2 to produce PuOx+1(NO3)y-1(-), which in most cases corresponds to an increase in the oxidation state of plutonium. Plutonyl species, Pu(V)O2(NO3)2(-) and Pu(VI)O2(NO3)3(-), were produced from Pu(III)(NO3)4(-) and Pu(IV)(NO3)5(-), respectively, by the elimination of two NO2 molecules. CID of Pu(VI)O2(NO3)3(-) resulted in NO2 elimination to yield PuO3(NO3)2(-), in which the oxidation state of plutonium could be VII, a known oxidation state in condensed phase but not yet in the gas phase. Density functional theory confirmed the nature of Pu(V)O2(NO3)2(-) and Pu(VI)O2(NO3)3(-) as plutonyl(V/VI) cores coordinated by bidentate equatorial nitrate ligands. The computed structure of PuO3(NO3)2(-) is essentially a plutonyl(VI) core, Pu(VI)O2(2+), coordinated in the equatorial plane by two nitrate ligands and one radical oxygen atom. The computations indicate that in the ground spin-orbit free state of PuO3(NO3)2(-), the unpaired electron of the oxygen atom is antiferromagnetically coupled to the spin-triplet state of the plutonyl core. The results indicate that Pu(VII) is not a readily accessible oxidation state in the gas phase, despite that it is stable in solution and solids, but rather that a Pu(VI)-O· bonding configuration is favored, in which an oxygen radical is involved.

This work proposes an integrated workflow for secondary use of medical data to serve feasibility studies, and the prescreening and monitoring of research studies. All research issues are initially addressed by the Clinical Research Office through a research portal and subsequently redirected to relevant experts in the determined field of concentration. For secondary use of data, the workflow is then based on the clinical data warehouse of the hospital. A datamart with potentially eligible research candidates is constructed. Datamarts can either produce aggregated data, de-identified data, or identified data, according to the kind of study being treated. In conclusion, integrating the secondary use of data process into a general research workflow allows visibility of information technologies and improves the accessability of clinical data.

Computational chemistry currently lacks ad hoc tools for probing the nature of chemical bonds in heavy and superheavy-atom systems where the consideration of spin-orbit coupling (SOC) effects is mandatory. We report an implementation of the Quantum Theory of Atoms-In-Molecules in the framework of two-component relativistic calculations. Used in conjunction with the topological analysis of the Electron Localization Function, we show for astatine (At) species that SOC significantly lowers At electronegativity and boosts its propensity to make charge-shift bonds. Relativistic spin-dependent effects are furthermore able to change some bonds from mainly covalent to charge-shift type. The implication of the disclosed features regarding the rationalization of the labeling protocols used in nuclear medicine for (211)At radioisotope nicely illustrates the potential of the introduced methodology for investigating the chemistry of (super)heavy elements.

Iron chelation in tumoral cells has been reported as potentially useful during antitumoral treatment. Our aim was to develop new polyaminoquinoline iron chelators targeting tumoral cells. For this purpose, we designed, synthesized, and evaluated the biological activity of a new generation of iron chelators, which we named Quilamines, based on an 8-hydroxyquinoline (8-HQ) scaffold linked to linear polyamine vectors. These were designed to target tumor cells expressing an overactive polyamine transport system (PTS). A set of Quilamines bearing variable polyamine chains was designed and assessed for their ability to interact with iron. Quilamines were also screened for their cytostatic/cytotoxic effects and their selective uptake by the PTS in the CHO cell line. Our results show that both the 8-HQ moiety and the polyamine part participate in the iron coordination. HQ1-44, the most promising Quilamine identified, presents a homospermidine moiety and was shown to be highly taken up by the PTS and to display an efficient antiproliferative activity that occurred in the micromolar range. In addition, cytotoxicity was only observed at concentrations higher than 100 μM. We also demonstrated the high complexation capacity of HQ1-44 with iron while much weaker complexes were formed with other cations, indicative of a high selectivity. We applied the density functional theory to study the binding energy and the electronic structure of prototypical iron(III)-Quilamine complexes. On the basis of these calculations, Quilamine HQ1-44 is a strong tridentate ligand for iron(III) especially in the form of a 1:2 complex.

We present an original formulation of the electron localization function (ELF) in the field of relativistic two-component DFT calculations. Using I2 and At2 species as a test set, we show that the ELF analysis is suitable to evaluate the spin-orbit effects on the electronic structure. Beyond these examples, this approach opens up new opportunities for the bonding analysis of large molecular systems involving heavy and superheavy elements.

A cost-effective computational methodology designed to study astatine (At) chemistry in aqueous solution has been established. It is based on two-component spin-orbit density functional theory calculations and solvation calculations using the conductor-like polarizable continuum model in conjunction with specific astatine cavities. Theoretical calculations are confronted with experimental data measured for complexation reactions between metallic forms of astatine (At(+) and AtO(+)) and inorganic ligands (Cl(-), Br(-) and SCN(-)). For each reaction, both 1:1 and 1:2 complexes are evidenced. The experimental trends regarding the thermodynamic constants (K) can be reproduced qualitatively and quantitatively. The mean signed error on computed Log K values is -0.4, which corresponds to a mean signed error smaller than 1 kcal mol(-1) on free energies of reaction. Theoretical investigations show that the reactivity of cationic species of astatine is highly sensitive to spin-orbit coupling and solvent effects. At the moment, the presented computational methodology appears to be the only tool to gain an insight into astatine chemistry at a molecular level., (This journal is © the Owner Societies 2011)

The gas phase structures of epibatidine, one of the most potent agonists of nicotinic acetylcholine receptors (nAChRs), are determined by means of infrared multiphoton dissociation (IRMPD) spectroscopy and quantum chemistry calculations. Comparison of the experimental and theoretical spectra provides evidence that about 15% of epibatidine is protonated on the Nsp(2) nitrogen in the gas phase. In contrast, the computational study of deschloroepibatidine shows that in the gas phase, the molecule is present only protonated on the Nsp(2) nitrogen. The main minima of the Nsp(2) protonated forms of the two molecules are strongly stabilized by intramolecular CH···Nsp(3) hydrogen bonds. The fundamental insights obtained in the present study on these two important nAChRs agonists show how subtle chemical modifications can have a deep impact on important physicochemical properties.

Synthesis of alternating pyridine-pyrrole molecular strands composed of two electron-rich pyrrole units (donors) sandwiched between three pyridinic cores (acceptors) is described. The envisioned strategy was a smooth electrosynthesis process involving ring contraction of corresponding tripyridyl-dipyridazine precursors. 2,6-Bis[6-(pyridazin-3-yl)]pyridine ligands 2a-c bearing pyridine residues at the terminal positions were prepared in suitable quantities by a Negishi metal cross-coupling procedure. The yields of heterocyclic coupling between 2-pyridyl zinc bromide reagents 12a-c and 2,6-bis(6-trifluoromethanesulfonylpyridazin-3-yl)pyridine increased from 68 to 95% following introduction of electron-donating methyl groups on the metallated halogenopyridine units. Favorable conditions for preparative electrochemical reduction of tripyridyl-dipyridazines 2b,c were established in THF/acetate buffer (pH 4.6)/acetonitrile to give the targeted 2,6-bis[5-(pyridin-2-yl)pyrrol-2-yl]pyridines 1b and 1c in good yields. The absorption behavior of the donor-acceptor tripyridyl-dipyrrole ligands was evaluated and compared to theoretical calculations. Highly fluorescent properties of these chromophores were found (ν(em)≈2 × 10(4) cm(-1) in MeOH and CH(2)Cl(2)), and both pyrrolic ligands exhibit a remarkable quantum yield in CH(2)Cl(2) (φ(f)=0.10). Structural studies in the solid state established the preferred cis conformation of the dipyrrolic ligands, which adopting a planar arrangement with an embedded molecule of water having a complexation energy exceeding 10 kcal mol(-1). The ability of the tripyridyl-dipyrrole to complex two copper(II) ions in a pentacoordinate square was investigated.

The conformational preferences of a new bis-pyrrole derivative and its bis-pyridazine precursor have been investigated through quantum chemistry calculations (HF, DFT(MPWB1K), LMP2) and observations in the solid state. The global energetic minima are planar for both structures, with the conformational preferences being explained by pi-electronic conjugation between the aromatic systems and the occurrence of intramolecular hydrogen bonds (HB). For the bis-pyridazine derivative, the all-anti preferred conformation results from CH...Nsp(2) HB whereas the all-syn conformation of the bis-pyrrole is partly due to NH...Nsp(2) HB. For both systems, the validity of the theoretical conformational features is confirmed through the excellent agreement with the experimental data available. Calculations of electrostatic potential computed on the molecular surface of the various structures and their building blocks allow the variations to be rationalized in terms of molecular structure and are used to analyze the HB donor and acceptor sites of the compounds. The HB interaction sites predicted from the quantum chemical calculations are confirmed through the HB interactions observed in relevant crystal structures.

The X-ray diffraction structure of (-)-lobeline, a high affinity nicotinic ligand, has been determined. A comparison with its hydrobromide and hydrochloride salts shows the great flexibility of the two lateral chains of the N-methylpiperidine ring. Infrared studies carried out on the same species, in the solid state and in solution, reveal the propensity of this molecular framework to accommodate very specific hydrogen bonds (HBs) depending on the state-neutral or protonated-of the molecule. In solution, a strong internal HB between the hydroxyl group and the piperidine nitrogen gives an exceptionally high HB affinity to the hydroxyl oxygen of the lobeline base. In the ionic form, both NH+ and OH groups of the molecule cooperate as HB donors to chelate the counterion. These interactions provide very stable structures and indicate that protonated lobeline can also act as a strong HB donor.

The DNA Methylation Database (MethDB; http://www.methdb.net) is a public database dedicated to DNA methylation. It attempts to store all data about DNA methylation in a common source. MethDB can be searched in different ways, ranging from a simple browse mode to detailed queries for sequence-specific DNA methylation profiles and patterns, total methylation content data or environmental conditions that can influence the methylation state of DNA. Currently, the database contains 2570 values for methylation content and 5278 methylation patterns and profiles for a total of 83 genes or loci. MethDB is an annotated database, and the scientific community is invited to submit their own data (submit@methdb.de).