Contributions beyond direct random-phase approximation in the binding energy of solid ethane, ethylene, and acetylene.

The random-phase approximation (RPA) includes a subset of higher than second-order correlation-energy contributions, but stays in the same complexity class as the second-order Møller-Plesset perturbation theory (MP2) in both Gaussian-orbital and plane-wave codes. This makes RPA a promising ab initio electronic structure approach for the binding energies of molecular crystals. Still, some issues stand out in practical applications of RPA. Notably, compact clusters of nonpolar molecules are poorly described, and the interaction energies strongly depend on the reference single-determinant state. Using the many-body expansion of the binding energy of a crystal, we investigate those issues and the effect of beyond-RPA corrections. We find the beneficial effect of quartic-scaling exchange and non-ring coupled-cluster doubles corrections. The nonadditive interactions in compact trimers of molecules are improved by using the self-consistent Hartree-Fock orbitals instead of the usual Kohn-Sham states, but this kind of orbital input also leads to underestimated dimer energies. Overall, a substantial improvement over the RPA with a renormalized singles approach is possible at a modest quartic-scaling cost, which encourages further research into additional RPA corrections.

Magnetically Induced Binary Ferrocene with Oxidized Iron.

Ferrocene is perhaps the most popular and well-studied organometallic molecule, but our understanding of its structure and electronic properties has not changed for more than 70 years. In particular, all previous attempts of chemically oxidizing pure ferrocene by binding directly to the iron center have been unsuccessful, and no significant change in structure or magnetism has been reported. Using a metal organic framework host material, we were able to fundamentally change the electronic and magnetic structure of ferrocene to take on a never-before observed physically stretched/bent high-spin Fe(II) state, which readily accepts O2 from air, chemically oxidizing the iron from Fe(II) to Fe(III). We also show that the binding of oxygen is reversible through temperature swing experiments. Our analysis is based on combining Mößbauer spectroscopy, extended X-ray absorption fine structure, in situ infrared, SQUID, thermal gravimetric analysis, and energy dispersive X-ray fluorescence spectroscopy measurements with ab initio modeling.

Assessment of random phase approximation and second-order Møller-Plesset perturbation theory for many-body interactions in solid ethane, ethylene, and acetylene.

The relative energies of different phases or polymorphs of molecular solids can be small, less than a kilojoule/mol. A reliable description of such energy differences requires high-quality treatment of electron correlations, typically beyond that achievable by routinely applicable density functional theory (DFT) approximations. At the same time, high-level wave function theory is currently too computationally expensive. Methods employing an intermediate level of approximations, such as Møller-Plesset (MP) perturbation theory and the random phase approximation (RPA), are potentially useful. However, their development and application for molecular solids has been impeded by the scarcity of necessary benchmark data for these systems. In this work, we employ the coupled-cluster method with singles, doubles, and perturbative triples to obtain a reference-quality many-body expansion of the binding energy of four crystalline hydrocarbons with a varying π-electron character: ethane, ethene, and cubic and orthorhombic forms of acetylene. The binding energy is resolved into explicit dimer, trimer, and tetramer contributions, which facilitates the analysis of errors in the approximate approaches. With the newly generated benchmark data, we test the accuracy of MP2 and non-self-consistent RPA. We find that both of the methods poorly describe the non-additive many-body interactions in closely packed clusters. Using different DFT input states for RPA leads to similar total binding energies, but the many-body components strongly depend on the choice of the exchange-correlation functional.

Cost-of-illness analysis and regression modeling in cystic fibrosis: a retrospective prevalence-based study.

BACKGROUND: Economic data pertaining to cystic fibrosis (CF), is limited in Europe generally, and completely lacking in Central and Eastern Europe. We performed an analysis of all direct costs associated with CF relative to key disease features and laboratory examinations. METHODS: A retrospective prevalence-based cost-of-illness (COI) study was performed in a representative cohort of 242 CF patients in the Czech Republic, which represents about 65 % of all Czech CF patients. Medical records and invoices to health insurance companies for reference year 2010 were analyzed. RESULTS: The mean total health care costs were €14,486 per patient, with the majority of the costs going towards medicinal products and devices (€10,321). Medical procedures (€2676) and inpatient care (€1829) represented a much smaller percentage of costs. A generalized linear model showed that the strongest cost drivers, for all cost categories, were associated with patient age and lung disease severity (assessed using the FEV1 spirometric parameter), when compounded by chronic Pseudomonas aeruginosa airway infections. Specifically, maximum total costs are around the age 16 years; a FEV1 increase of 1 % point represented a cost decrease of: 0.9 % (medicinal products), 1.7 % (total costs), 2.8 % (procedures) and 7.0 % (inpatient care). CONCLUSIONS: COI analysis and regression modeling using the most recent data available can provide a better understanding of the overall economic CF burden. A comparison of our results with other methodologically similar studies demonstrates that although overall costs may differ, FEV1 can nonetheless be utilized as a generally transferrable indicator of the relative economic impact of CF.

Placental passage of olomoucine II, but not purvalanol A, is affected by p-glycoprotein (ABCB1), breast cancer resistance protein (ABCG2) and multidrug resistance-associated proteins (ABCCs).

1. Purine cyclin-dependent kinase inhibitors have recently been recognised as promising candidates for the treatment of various cancers. While pharmacodynamic properties of these compounds are relatively well understood, their pharmacokinetics including possible interactions with placental transport systems have not been characterised to date. 2. In this study, we investigated transplacental passage of olomoucine II and purvalanol A in rat focusing on possible role of p-glycoprotein (ABCB1), breast cancer resistance protein (ABCG2) and/or multidrug resistance-associated proteins (ABCCs). Employing the in situ method of dually perfused rat term placenta, we demonstrate transplacental passage of both olomoucine II and purvalanol A against the concentration gradient in foetus-to-mother direction. Using several ATP-binding cassette (ABC) drug transporter inhibitors, we confirm the participation of ABCB1, ABCG2 and ABCCs transporters in the placental passage of olomoucine II, but not purvalanol A. 3. Transplacental passage of olomoucine II and purvalanol A from mother to foetus is significantly reduced by active transporters, restricting thereby foetal exposure and providing protection against harmful effects of these xenobiotics. Importantly, we demonstrate that in spite of their considerable structural similarity, the two molecules utilise distinct placental transport systems. These facts should be kept in mind when introducing these prospective anticancer candidates and/or their analogues into the clinical area.

Dinaciclib, a cyclin-dependent kinase inhibitor, is a substrate of human ABCB1 and ABCG2 and an inhibitor of human ABCC1 in vitro.

Dinaciclib is a novel cyclin-dependent kinase inhibitor (CDKI) with significant activity against various cancers in vitro and in vivo. ABC efflux transporters play an important role in drug disposition and are responsible for multidrug resistance in cancer cells. Inhibitors and substrates of these transporters may participate in pharmacokinetic drug-drug interactions (DDIs) that alter drug disposition during pharmacotherapy. To assess such risks associated with dinaciclib we evaluated its possible effects on efflux activities of ABCB1, ABCC1 and ABCG2 transporters in vitro. Monolayer transport, XTT cell proliferation, ATPase and intracellular accumulation assays were employed. Here, we show that the transport ratio of dinaciclib was far higher across monolayers of MDCKII-ABCB1 and MDCKII-ABCG2 cells than across MDCKII parental cell layers, demonstrating that dinaciclib is a substrate of ABCB1 and ABCG2. In addition, overexpression of ABCB1, ABCG2 and ABCC1 conferred resistance to dinaciclib in MDCKII cells. In ATPase assays, dinaciclib decreased stimulated ATPase activity of ABCB1, ABCG2 and ABCC1, confirming it has interactive potential toward all three transporters. Moreover, dinaciclib significantly inhibited ABCC1-mediated efflux of daunorubicin (EC50=18 µM). The inhibition of ABCC1 further led to a synergistic effect of dinaciclib in both MDCKII-ABCC1 and human cancer T47D cells, when applied in combination with anticancer drugs. Taken together, our results suggest that ABC transporters can substantially affect dinaciclib transport across cellular membranes, leading to DDIs. The DDIs of dinaciclib with ABCC1 substrate chemotherapeutics might be exploited in novel cancer therapies.

The nature of bonding and electronic properties of graphene and benzene with iridium adatoms.

Recent theoretical simulations predicted that graphene decorated with Ir adatoms could realize a two-dimensional topological insulator with a substantial band gap. Our understanding of how the electronic properties of graphene change in the presence of metal adatoms is however still limited, as the binding is quite complex involving static and dynamic correlation effects together with relativistic contributions, which makes the theoretical description of such systems quite challenging. We applied the quantum chemical complete active space second order perturbation theory (CASPT2) method and density functional theory beyond the standard local density functional approach including relativistic spin-orbit coupling (SOC) effects on Ir-benzene and Ir-graphene complexes. The CASPT2-SOC method revealed a strong binding affinity of Ir for benzene (33.1 kcal mol(-1)) at a 1.81 Å distance, which was of a single reference character, and a weaker binding affinity (6.3 kcal mol(-1)) at 3.00 Å of a multireference character. In the Ir-graphene complex, the quartet ground-state of the Ir atom changed to the doublet state upon adsorption, and the binding energy predicted by optB86b-vdW-SOC functional remained high (33.8 kcal mol(-1)). In all cases the dynamic correlation effects significantly contributed to the binding. The density of states calculated with the hybrid functional HSE06 showed that the gap of 0.3 eV was induced in graphene by the adsorbed Ir atom even in scalar relativistic calculation, in contrast to metallic behaviour predicted by local density approximation. The results suggest that the strong correlation effects contribute to the opening of the band gap in graphene covered with the Ir adatoms. The value of the magnetic anisotropy energy of 0.1 kcal mol(-1) predicted by HSE06 is lower than those calculated using local functionals.

Zirconia--a stationary phase capable of the separation of polar markers of myocardial metabolism in hydrophilic interaction chromatography.

Creatine, phosphocreatine, and adenine nucleotides are highly polar markers of myocardial metabolism that are poorly retained on RP silica sorbents. Zirconia represents an alternative material to silica with high promise to be used in hydrophilic interaction chromatography (HILIC). This study describes a first systematic investigation of the ability of ZrO2 to separate creatine, phosphocreatine, adenosine 5'-monophosphate, adenosine 5'-diphosphate, and adenosine 5'-triphosphate and compares the results with those obtained on TiO2 . All analytes showed a HILIC-like retention pattern when mobile phases of different strengths were tested. Stronger retention and better column performance were achieved in organic-rich mobile phases as compared to aqueous conditions, where poor retention and insufficient column performance were observed. The effect of mobile phase pH and ionic strength was evaluated as well. The analysis of myocardial tissue demonstrated that all compounds were separated in a relevant biological material and thus proved ZrO2 as a promising phase for HILIC of biological samples that deserves further investigation.

Simultaneous determination of the novel thiosemicarbazone anti-cancer agent, Bp4eT, and its main phase I metabolites in plasma: application to a pilot pharmacokinetic study in rats.

Novel thiosemicarbazone metal chelators are extensively studied anti-cancer agents with marked and selective activity against a wide variety of cancer cells, as well as human tumor xenografts in mice. This study describes the first validated LC-MS/MS method for the simultaneous quantification of 2-benzoylpyridine 4-ethyl-3-thiosemicarbazone (Bp4eT) and its main metabolites (E/Z isomers of the semicarbazone structure, M1-E and M1-Z, and the amidrazone metabolite, M2) in plasma. Separation was achieved using a C18 column with ammonium formate/acetonitrile mixture as the mobile phase. Plasma samples were treated using solid-phase extraction on 96-well plates. This method was validated over the concentration range of 0.18-2.80 µM for Bp4eT, 0.02-0.37 µM for both M1-E and M1-Z, and 0.10-1.60 µM for M2. This methodology was applied to the analysis of samples from in vivo experiments, allowing for the concentration-time profile to be simultaneously assessed for the parent drug and its metabolites. The current study addresses the lack of knowledge regarding the quantitative analysis of thiosemicarbazone anti-cancer drugs and their metabolites in plasma and provides the first pharmacokinetic data on a lead compound of this class.

Olomoucine II, but not purvalanol A, is transported by breast cancer resistance protein (ABCG2) and P-glycoprotein (ABCB1).

Purine cyclin-dependent kinase inhibitors have been recognized as promising candidates for the treatment of various cancers; nevertheless, data regarding interaction of these substances with drug efflux transporters is still lacking. Recently, we have demonstrated inhibition of breast cancer resistance protein (ABCG2) by olomoucine II and purvalanol A and shown that these compounds are able to synergistically potentiate the antiproliferative effect of mitoxantrone, an ABCG2 substrate. In this follow up study, we investigated whether olomoucine II and purvalanol A are transported by ABCG2 and ABCB1 (P-glycoprotein). Using monolayers of MDCKII cells stably expressing human ABCB1 or ABCG2, we demonstrated that olomoucine II, but not purvalanol A, is a dual substrate of both ABCG2 and ABCB1. We, therefore, assume that pharmacokinetics of olomoucine II will be affected by both ABCB1 and ABCG2 transport proteins, which might potentially result in limited accumulation of the compound in tumor tissues or lead to drug-drug interactions. Pharmacokinetic behavior of purvalanol A, on the other hand, does not seem to be affected by either ABCG2 or ABCB1, theoretically favoring this drug in the potential treatment of efflux transporter-based multidrug resistant tumors. In addition, we observed intensive sulfatation of olomoucine II in MDCKII cell lines with subsequent active efflux of the metabolite out of the cells. Therefore, care should be taken when performing pharmacokinetic studies in MDCKII cells, especially if radiolabeled substrates are used; the generated sulfated conjugate may largely contaminate pharmacokinetic analysis and result in misleading interpretation. With regard to chemical structures of olomoucine II and purvalanol A, our data emphasize that even drugs with remarkable structure similarity may show different pharmacokinetic behavior such as interactions with ABC transporters or biotransformation enzymes.

Identification of in vitro metabolites of the novel anti-tumor thiosemicarbazone, DpC, using ultra-high performance liquid chromatography-quadrupole-time-of-flight mass spectrometry.

Di-2-pyridylketone-4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC) is a promising analogue of the dipyridyl thiosemicarbazone class currently under development as a potential anti-cancer drug. In fact, this class of agents shows markedly greater anti-tumor activity and selectivity than the clinically investigated thiosemicarbazone, Triapine®. However, further development of DpC requires detailed data concerning its metabolism. Therefore, we focused on the identification of principal phase I and II metabolites of DpC in vitro. DpC was incubated with human liver microsomes/S9 fractions and the samples were analyzed using ultra-performance liquid chromatography (UPLC(TM)) with electrospray ionization quadrupole-time-of-flight (Q-TOF) mass spectrometry. An Acquity UPLC BEH C(18) column was implemented with 2 mM ammonium acetate and acetonitrile in gradient mode as the mobile phase. The chemical structures of metabolites were proposed based on the accurate mass measurement of the protonated molecules as well as their main product ions. Ten phase I and two phase II metabolites were detected and structurally described. The metabolism of DpC occurred via oxidation of the thiocarbonyl group, hydroxylation and N-demethylation, as well as the combination of these reactions. Conjugates of DpC and the metabolite, M10, with glucuronic acid were also observed as phase II metabolites. Neither sulfate nor glutathione conjugates were detected. This study provides the first information about the chemical structure of the principal metabolites of DpC, which supports the development of this promising anti-cancer drug and provides vital data for further pharmacokinetic and in vivo metabolism studies.

LC-MS/MS identification of the principal in vitro and in vivo phase I metabolites of the novel thiosemicarbazone anti-cancer drug, Bp4eT.

The iron chelator, 2-benzoylpyridine-4-ethyl-3-thiosemicarbazone (Bp4eT), was identified as a lead compound of the 2-benzoylpyridine thiosemicarbazone series, which were designed as potential anti-cancer agents. This ligand has been shown to possess potent anti-proliferative activity with a highly selective mechanism of action. However, further progress in the development of this compound requires data regarding its metabolism in mammals. The aim of this study was to identify the main in vitro and in vivo phase I metabolites of Bp4eT using liquid chromatography tandem mass spectrometry (LC-MS/MS). Two metabolites were detected after incubation of this drug with rat and human liver microsomal fractions. Based on LC-MS(n) analysis, the metabolites were demonstrated to be 2-benzoylpyridine-4-ethyl-3-semicarbazone and N (3)-ethyl-N (1)-[phenyl(pyridin-2-yl)methylene]formamidrazone, with both resulting from the oxidation of the thiocarbonyl group. The identity of these metabolites was further shown by LC-MS/MS analysis of these latter compounds which were prepared by oxidation of Bp4eT with hydrogen peroxide and their structures confirmed by nuclear magnetic resonance and infrared spectra. Both the semicarbazone and the amidrazone metabolites were detected in plasma, urine, and feces after i.v. administration of Bp4eT to rats. In addition, another metabolite that could correspond to hydroxylated amidrazone was found in vivo. Thus, oxidative pathways play a major role in the phase I metabolism of this promising anti-tumor agent. The outcomes of this study will be further utilized for: (1) the development and validation of the analytical method for the quantification of Bp4eT and its metabolites in biological materials; (2) to design pharmacokinetic experiments; and to (3) evaluate the potential contribution of the individual metabolites to the pharmacodynamics/toxico-dynamics of this novel anti-proliferative agent.

Understanding the interaction of the porphyrin macrocycle to reactive metal substrates: structure, bonding, and adatom capture.

We investigate the adsorption and conformation of free-base porphines on Cu(110) using STM, reflection absorption infrared spectroscopy, and periodic DFT calculations in order to understand how the central polypyrrole macrocycle, common to all porphyrins, interacts with a reactive metal surface. We find that the macrocycle forms a chemisorption bond with the surface, arising from electron donation into down-shifted and nearly degenerate unoccupied porphine π-orbitals accompanied with electron back-donation from molecular π-orbitals. Our calculations show that van der Waals interactions give rise to an overall increase in the adsorption energy but only minor changes in the adsorption geometry and electronic structure. In addition, we observe copper adatoms being weakly attracted to adsorbed porphines at specific molecular sites. These results provide important insights into porphyrin-surface interactions that, ultimately, will govern the design of robust surface-mounted molecular devices based on this important class of molecules.

Development of an LC-MS/MS method for analysis of interconvertible Z/E isomers of the novel anticancer agent, Bp4eT.

This study was focused on a liquid chromatography/tandem mass spectrometry (LC/MS/MS) method development for quantification of a novel potential anticancer agent, 2-benzoylpyridine 4-ethyl-3-thiosemicarbazone (Bp4eT), in aqueous media. Solid Bp4eT was found to consist predominantly of the Z isomer, while in aqueous media, both isomers coexist. Sufficient separation of both isomers was achieved on a Synergi 4u Polar RP column with a mobile phase composed of 2 mM ammonium formate, acetonitrile, and methanol (30:63:7; v/v/v). The photo diode array analysis of both isomers demonstrated different absorption spectra which hindered UV-based quantification. However, an equal and reproducible response was found for both isomers using an MS detector, which enables the determination of the total content of Bp4eT (i.e., both E- and Z- isomeric forms) by summation of the peak areas of both isomers. 2-Hydroxy-1-naphthylaldehyde 4-methyl-3-thiosemicarbazone (N4mT) was selected as the internal standard. Quantification was performed in selective reaction monitoring using the main fragments of [M+H](+) (240 m/z for Bp4eT and 229 m/z for N4mT). The method was validated over 20-600 ng/ml. This procedure was applied to a preformulation study to determine the proper vehicle for parenteral administration. It was found that Bp4eT was poorly soluble in aqueous media. However, the solubility can be effectively improved using pharmaceutical cosolvents. In fact, a 1:1 mixture of PEG 300/0.14 M saline markedly increased solubility and may be a useful drug formulation for intravenous administration. This investigation further accelerates development of novel anticancer thiosemicarbazones. The described methods will be useful for analogs currently under development and suffering the same analytical issue.

HPLC methods for determination of two novel thiosemicarbazone anti-cancer drugs (N4mT and Dp44mT) in plasma and their application to in vitro plasma stability of these agents.

The aim of this study was to develop and validate HPLC methods for the determination in plasma of two novel thiosemicarbazone anti-tumour drugs developed in our laboratories (Dp44mT and N4mT). The appropriate separations were achieved using a HS F5 HPLC column with the mobile phase composed of a mixture of either acetate buffer/EDTA or EDTA and acetonitrile (62:38 and 50:50, v/v, respectively). The plasma samples were pretreated with SPE (phenyl and C18, respectively). Furthermore, these methods were successfully applied to in vitro plasma stability experiments. The investigation has clearly shown that both thiosemicarbazones are markedly more stable in plasma than their aroylhydrazone forerunners.

Development and validation of HPLC-DAD methods for the analysis of two novel iron chelators with potent anti-cancer activity.

Di-2-pyridylketone isonicotinoyl hydrazone (PKIH) and di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT) novel iron chelators which possess marked anti-cancer activity in vivo. However, further progress in the development of these drug candidates requires precise and convenient methods for their qualitative and quantitative analysis. The aim of this study was to develop and validate HPLC methods suitable for the purity and stability evaluation of Dp44mT and PKIH and subsequently to employ these methods in stress tests addressing their chemical stability. The chromatographic analyses of both chelators were accomplished via HPLC using a Discovery HSF5 column (25 cm x 4 mm; 5 microm). For separation of Dp44mT and its synthetic precursors, the mobile phase was composed of a mixture of 2 mM EDTA and acetonitrile in a ratio 60:40 (v/v). A desirable separation of PKIH from its synthetic precursors was achieved with a mixture of 0.01 M phosphate buffer (pH 3.0), methanol and acetonitrile in a ratio of 65:21:14 (v/v/v) with the addition of EDTA (2 mM). In order to confirm the utility of these HPLC methods for measuring these drugs and their stability, Dp44mT and PKIH were subjected to chemical stress tests. These experiments showed that Dp44mT was relatively stable against hydrolytic degradation, but quite sensitive to oxidation. On the other hand, PKIH was slightly sensitive to acid-catalyzed hydrolysis, but it was relatively stable under other tested conditions. Furthermore, these studies confirmed the utility of these methods not only for appropriate evaluation of purity but also stability. The analytical methods developed and validated in this study, as well as the basic data on the chemical stability, should further support the development of both these novel anti-cancer chelators as promising drug candidates.

Comparison of different stationary phases for bioanalytical studies of biologically active compounds.

In this study, the chromatographic behaviour of four mixtures of compounds was tested on columns possessing various surface properties. Cocaine, dimefluron, nabumetone, and tramadol were chosen as the test compounds. Cocaine is a tropane alkaloid, which is relatively often abused as a drug. This is why many papers have already been written about its determination in human biological samples. Dimefluron, a derivative of benzo[c]fluorene, is a new perspective drug being investigated for its potential antineoplastic effects. Nabumetone is a non-steroidal anti-inflammatory prodrug used for treatment of inflammatory and degenerative rheumatic diseases. Tramadol, derived from an opioid structure is used as an anodyne for treatment of severe pain. As a medicament it is usually determined either in biological samples or in pharmaceuticals. The above-mentioned model drugs were separated using chromatographic columns with C18, C8, palmitamidopropyl, and pentafluorophenylpropyl chains. The best conditions for separation of the individual compounds and their metabolites were chosen on the basis of resolution, retention times, and peak symmetry.

HPLC determination of a novel aroylhydrazone iron chelator (o-108) in rabbit plasma and its application to a pilot pharmacokinetic study.

A high performance liquid chromatographic method for the determination of a biocompatible iron chelator, pyridoxal 2-chlorobenzoyl hydrazone (o-108), in rabbit plasma was developed and validated. The separation was achieved on a C18 column with the mobile phase composed of a mixture of 0.01 M phosphate buffer (pH 6) with the addition of EDTA (2 mM), methanol and acetonitrile (42:24:14; v/v/v). The method was validated with respect to selectivity, linearity (0.8-150 microg/mL), intra- and inter-day variability and stability. This method was successfully applied to the analysis of the samples obtained from a pilot pharmacokinetic experiment, in which the chelator was administered intravenously to rabbits.