Parallelized implementation of the coupled cluster singles doubles with non-iterative triples in the MOLCAS program suite is described. The code benefits from the Cholesky decomposition of two-electron integrals and the algorithm is particularly designed for calculations using reduced optimized virtual orbital space. Different aspects of parallelization and its efficiency are discussed based on our recent successful calculations for medium sized molecules involving more than 1000 basis functions.
The novel pyrimidine carboacyclonucleoside analogues containing propargylated aryl side chains were synthesized via palladium-catalyzed cross-coupling reactions as a key step. The synthesized compounds were screened for their antibacterial activity against four microorganisms: Staphylococcus aureus (CIP 53.154; Gram positive), Enterococcus hirae (CIP 58.55; Gram positive), Pseudomonas aeruginosa (CIP A22; Gram negative), Escherichia coli (CIP 54.8; Gram negative). Some of the prepared products showed promising antibacterial activity against the nosocomial E. hirae .
Using chronoamperometric measurements at pH 12 it is shown that the oxidation mechanism of niazid adsorbed on the mercury electrode changes with respect to the mechanism reported in the literature for the electrooxidation of the molecules reaching the electrode by diffusion. A compact monolayer of niazid molecules is formed on the electrode surface, being the hydrazide oxidized through a two-electron process. The oxidation product is not able to dissociate a H(+) ion, and the oxidation process does not proceeds beyond. For isoniazid the monolayer never becomes compact.
A series of copper-modified titanium dioxide (Cu/TiO 2 ) nanoparticles were synthesized via one-step sol-gel method. The crystal structure and chemical properties were characterized using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The Cu/TiO 2 nanoparticles were applied to CO 2 photoconversion and the yield of formaldehyde was used to evaluate the photocatalytic performance. The optimum amount of copper modifying was 0.6 wt.% and the yield of formaldehyde was 946 μmol/g cat under UV illumination for 6 h. 20 wt.% Cu/TiO 2 also performed a high photocatalytic activity, which yielded 433 μmol/g cat formaldehyde under UV illumination for 6 h.
The formation of polypyrrole (PPy) layers by electrochemical polymerisation of pyrrole (Py) on paraffin impregnated graphite electrode (PIGE) was studied. Electrochemical oxidation of Py was studied by means of cyclic voltammetry (CV) and the morphology of the deposited layers was investigated with scanning electron microscope (SEM). The structure and quality of PPy layers on PIGE depends on monomer concentration, pH value, stirring intensity and scan rate during the polymerisation process.
Electrochemical behavior of genotoxic nitro derivatives of quinoline, namely 5-nitroquinoline (5-NQ), 6-nitroquinoline (6-NQ) and 8-nitroquinoline (8-NQ), was investigated by DC tast polarography (DCTP) and differential pulse polarography (DPP), both at a classical dropping mercury electrode (DME), and by differential pulse voltammetry (DPV) and adsorptive stripping differential pulse voltammetry (AdSDPV), both at a miniaturized hanging mercury drop minielectrode (HMDmE), in buffered aqueous (for 5-NQ) or aqueous-methanolic (for 6-NQ and 8-NQ) solutions. Optimum conditions were found for the determination of 5-NQ, 6-NQ and 8-NQ by DCTP at DME (with limits of quantification, LQ ≈ 9 × 10–7, 3 × 10–7 and 2 × 10–6 mol l–1, respectively), by DPP at DME (LQ ≈ 1 × 10–8, 9 × 10–8 and 1 × 10–7 mol l–1, respectively), by DPV at HMDmE (LQ ≈ 2 × 10–8, 1 × 10–7 and 1 × 10–7 mol l–1, respectively), and by AdSDPV at HMDmE (LQ ≈ 1 × 10–8 mol l–1 for 8-NQ; an attempt at increasing the sensitivity using AdSDPV at HMDmE was not successful for 5-NQ and 6-NQ). Practical applicability of the developed methods was verified on the direct determination of the studied compounds in model samples of drinking and river water in submicromolar concentrations and on the determination in model samples of drinking and river water using preliminary separation and preconcentration by solid phase extraction (SPE) in nanomolar concentrations.
Catalytic potential of ammonium hypobromite in the one-pot synthesis of 3,4-dihydropyrimidin-2(1H)-ones from Biginelli-type condensation reaction between an aldehyde, β-keto ester and urea has been explored. The reaction proceeds under solvent-free conventional heating as well as microwave-irradiation conditions to afford the respective products in excellent yields.
The electrochemical oxidation behaviour of Drimarene Blue X-BLN (DB) has been investigated in phosphate buffers (pH 2.54–10.18) by cyclic and differential pulse voltammetry (DPV) at a glassy carbon electrode (GCE). The oxidation of DB dye generated well-defined pH-dependent two pairs of quasi-reversible anodic-cathodic peak couples. DB exhibited the second redox couple over the entire pH range, while the first redox couple disappeared for pH ≥ 6.70. The redox processes were adsorption-controlled. An electroanalytical method was developed for the determination of DB in phosphate buffer solution (pH 2.85) as supporting electrolyte using DPV. The anodic current heights varied linearly with DB concentrations in the ranges 2 × 10–6–3 × 10–5 and 6 × 10–6–3 × 10–5 mol l–1 with limits of detection (LOD) of 8.7 × 10–7 and 5.7 × 10–7 mol l–1 and limits of quantification (LOQ) of 2.9 × 10–6 and 1.9 × 10–6 mol l–1 for the first and second anodic peaks, respectively. Validation parameters, such as accuracy, precision and recovery were evaluated. The proposed method was successfully applied to the determination of DB in tap water and the analytical results compared well with those obtained by the spectrophotometric method.
The bridge function of hard spheres is accurately calculated from computer simulation data on the pair distribution function via the inverted Ornstein–Zernike equation at reduced densities ρ* ≡ Nσ3/V ranging from 0.2 to 1.02, i.e. from low densities through densities in a vicinity of the phase transition to crystal to densities of metastable fluid region. The data are used to propose an analytical representation of the bridge function as a function of the interparticle distance and density. They are further used to construct the so-called Duh– Haymet plot. It is demonstrated that a “general closure” to the Ornstein–Zernike equation in the form B(r) = f[γ(r)], where γ is the indirect (or series) correlation function, does not match the data. Nor does an extended closure B(r) = f[γ(r),ρ*] even in the simplest case of the one component hard sphere fluid. A relative success of literature closures to the Ornstein–Zernike equation is discussed.
Efficient synthesis of alkenylphosphonium salts via treatment of enolizable aliphatic aldehydes with tributyl[(trimethylsilyl)methylene]phosphorane has been described. The simple way for preparation of tributyl[(trimethylsilyl)methylene]phosphorane is also presented.
Nucleosides with an aromatic five-membered ring heterocycle (N, O, or S) fused at C4–C5 of pyrimidin-2-one were prepared by ring closures with 5-(alkyn-1-yl)pyrimidin-2-one intermediates, heterocyclic atom replacements, and ring closure with a 5-aminocytidine derivative. Ultraviolet absorption and emission properties of the autofluorescent products enabled studies on permeation and inhibition of the trans-cellular trafficking effected by human equilibrative nucleoside transporters (hENTs). Some of the autofluorescent nucleosides were shown to be potent and selective inhibitors of human concentrative nucleoside transporters (hCNTs) in a companion study reported elsewhere.
Novel bioengineering functional organoboron oligomers were synthesized by (i) amidolysis of oligo(maleic anhydride) (OMA) with 2-aminoethyldiphenylborinate (2-AEPB), (ii) esterification of organoboron oligomer (OMA-B) with α-hydroxy-ω-methoxypoly(ethylene oxide) (PEO) as a compatibilizer and (iii) conjugation of organoboron PEO branches (OMA-B-PEO) with folic acid as a taggering agent. Structure and composition of the synthesized oligomers were characterized by FTIR-ART and 1H (13C) NMR spectroscopy, chemical and physical analysis methods. Interaction of functional oligomers and oligomer···FA complex (OMA-B-PEO-F) with HeLa and L929 fibroblast cells were investigated by using different biochemical methods such as cytotoxicity, statistical, apoptotic and necrotic cell indexes, double staining and caspase-3 immunostaining, light and fluorescence inverted microscope analyses. It was found that citotoxisity and apoptotic/necrotic effects of oligomers significantly depend on the structure and composition of studied oligomers, and increase the following raw: OMA << OMA-B < OMA-B-PEO < OMA-B-PEO-F. A folic acid complex (MA-PEG-B-F) at 400 μg ml–1 (2.36 μmol ml–1) concentration as a therapeutic drug exhibits minimal toxcisity toward the fibroblast cells, but influential for HeLa cells.
A series ofN6-adenosine derivatives were synthesized by alkylation ofN6-acetyl-2′,3′,5′-tri-O-acetyladenosine (1) with alkyl halides and alcohols. It was shown that propargyl derivative2ais a good substrate for copper(I) catalyzed Huisgen [3+2] cycloaddition with azides. This click-reaction can be used for preparation of the libraries of 1,2,3-triazolyl modified adenosines. Biological activities ofN6-adenosines were studied in two plant and six human cancer cell assays. The remarkable parallel between cytokinin and cytotoxic activities was found. The most cytokinin active compounds3c–3eat the same time appeared to be the most potent cytotoxic agents.
The 1,4-anhydro-5-deoxy-6-thio-D-ribo-hexofuranitol (1) was prepared from 1,2-O-isopropylidene- a-D-glucose in 10 steps. In a key step treatment of the 1,2-O-isopropylidenehexofuranose derivative with BF3/Et3SiH effected deacetonization and reductive deoxygenation at carbon 1. Pulse radiolysis experiments with 6-thiohexofuranitol 1 and its disulfide derivative demonstrated formation of the ribosyl-based carbon-centered radical upon generation of 6-thiyl radical in basic medium. The proposed [1,5]-hydrogen shift abstraction with generation of the C3 radical mimics the initial substrate reaction of RNRs. The reversible H-atom transfer has been quantified and was correlated with the computed rate constants for the internal H atom abstraction from C1, C2, C3 and C4 by the thiyl radical. The energy barrier for the H3 and H4 abstractions were calculated to be most favorable with the corresponding barriers of 11.1 and 11.2 kcal/mol, respectively.
Complex [PdCl2L2], where L is a camphor hydrazone ligand, (1R, 4S)-1,7,7-trimethyl-3-( 2,2-dimethylhydrazone)-bicyclo[2.2.1]heptane-2,3-dione, efficiently promotes Markovnikov hydration of ethynylferrocene to acetylferrocene in aqueous methanol at room temperature. 1-Ferrocenylprop-1-yne and simple organic alkynes such as 1-octyne or ethynylbenzenes are not affected or polymerize under the reaction conditions.
In this study, two new amperometric carbon paste enzyme electrodes for determination of uric acid were developed. The carbon paste was prepared by mixing uricase enzyme, 1,4-benzoquinone or poly(vinylferrocene) (PVF) as a mediator, graphite powder, paraffin oil and then the paste was placed into cavity of a teflon electrode body. Determination of uric acid was performed by oxidation of enzymatically generated H2O2. The effects of enzyme loading, mediator amount, buffer type, pH, buffer concentration, working potential and temperature were investigated for both electrodes. The working range of the 1,4-benzoquinone modified enzyme electrode was 1.9 × 10–8–2.7 × 10–3 M, detection limit 1.9 × 10–8 M and response time 150 s. Optimum buffer type, pH, buffer concentration, working potential, temperature and amounts of enzyme and mediator for 1,4-benzoquinone modified enzyme electrode were found to be Tris, 8.0, 0.20 M, +0.25 V, 30 °C, 2.0 Unit and 13%, respectively. The working range of the PVF modified enzyme electrode was 7.4 × 10–8–7.0 × 10–3 M, detection limit 7.4 × 10–8 M and response time 120 s. Optimum buffer type, pH, buffer concentration, working potential, temperature and amounts of enzyme and mediator for PVF modified enzyme electrode were found to be phosphate, 8.0, 0.05 M, +0.70 and +0.30 V, 40 °C, 2.0 Unit and 10.9%, respectively. The repeatability, storage stability of the enzyme electrodes and interference effects were also investigated. Enzyme electrodes were used for determination of uric acid in serum samples and the results were in a good agreement with those obtained by commercial enzymatic kits.
The Fourier transform infrared (FTIR) spectrum of siderol, extracted from the aerial parts of Sideritis Gülendamii, has been measured in the range 4000–400 cm–1. Vibrational assignments and analyses of the fundamental modes of siderol were performed using the observed FTIR data recorded in the solid phase. The vibrational frequencies determined experimentally are compared with those obtained theoretically from density functional theory (DFT) and Hartee–Fock (HF) calculations. Optimized geometrical parameters of the title compound are in agreement with similar reported structures. The 1H and 13C NMR spectra of siderol have also been calculated by means of DFT and HF methods. The comparison between the experimental and the theoretical results indicates that density functional methods, B3LYP and MPW1PW91 with 6-31G(d) basis set, are able to provide satisfactory results for predicting NMR properties. On the basis of vibrational analyses, the thermodynamic properties of the title molecule have also been computed.
While direct Sonogashira coupling of 6-halopurines with methyl propiolate and with propargyl aldehyde was not successful, the corresponding orthoester and propargyl aldehyde diethylacetal reacted smoothly. Such prepared orthoester was then converted to the desired methylester by methanolysis, the acetal was too stable to be hydrolyzed. The obtained 6-ethynylpurines, bearing orthoester, acetal, methoxycarbonyl and for comparison also the phenyl substituent on the ethynyl group, were subjected to the cycloaddition reaction with cyclopentadiene, diazomethane and phenylazide. Electron deficient alkynylpurines were considerably more reactive in this reaction compared to the not activated phenylethynyl derivative. The prepared alkynylpurines exhibited medium cytostatic activity (IC50 = 2.6–15 μM), while the cycloadducts were inactive.
The possibility of determination of chloramphenicol by differential pulse voltammetry at four different carbon paste electrodes, in the full pH range (2–12) of Britton–Robinson (BR) buffer was investigated. Electrodes were prepared by mixing spectroscopic graphite powder or glassy carbon microbeads with mineral oil (Nujol) or tricresyl phosphate. Under optimal conditions (BR buffer pH 12, the electrode prepared from glassy carbon microbeads and tricresyl phosphate), linear calibration graph was obtained only in 10 –5 M chloramphenicol concentration range. Determination of lower concentrations of chloramphenicol was complicated by irreproducible peak of oxygen from the carbon paste which overlapped with peak of chloramphenicol. Addition of sodium sulfite removed the oxygen peak without influence on the peak of chloramphenicol. Under optimal conditions (electrode paste made from glassy carbon microbeads, BR buffer pH 10 and 0.5 M sodium sulfite), straight calibration line was obtained in the 10 –6 and 10 –5 M chloramphenicol concentration range. Limit of determination was 5 × 10 –7 mol/l.
Efficient and optimized procedure for the preparation of several acyclic nucleosides and acyclic nucleoside phosphonates substituted at the C-2′ position of the aliphatic part by the trifluoromethyl group is described. Trifluoromethyloxirane was found to be an excellent reagent for the introduction of the 1,1,1-trifluoropropan-2-ol moiety. Surprisingly, the next reaction of these 1,1,1-trifluoropropan-2-ols with the reagent for the introduction of the methylphosphonic residue afforded the desired phosphonates in very high yields and finally a novel simple and scalable procedure for the isolation of free phosphonic acids, after the reaction of dialkyl phosphonates with bromotrimethylsilane, was developed. Prepared compounds were evaluated for their biological properties, but none of the prepared phosphonic acids or acyclic nucleosides exhibits any antiviral, antiproliferative or anti-toxin activities.
