X‐Ray Structure Analyses of syn/anti‐Conformers of N‐Furfuroyl‐, N‐Benzoyl‐, and N‐Picolinoyl‐Substituted (2R)‐Bornane‐10,2‐sultam Derivatives

The synthesis and the X‐ray structure of the three new N‐(arylcarbonyl)‐substituted derivatives 2a – 2c of (2R)‐bornane‐10,2‐sultam are presented and discussed. Direct comparison of the solid‐state analyses shows that the dipole‐directed SO₂/C?O anti‐/syn‐conformations may be very sensitive to weak electronic/electrostatic repulsions of the heteroatom lone pairs. The optimum interactions are reached when the lone pair of the β‐positioned heteroatom is oriented in the O(3)?C(11)? N(1) plane. Such rare syn‐conformations may be observed with at least up to 1.8 kcal/mol higher energy as compared to their ground states. Additionally, these anti/syn‐conformations are also very sensitive to external influences such as, for example, the crystal‐packing forces.     

Novel Aspects of a Convenient Synthesis and of Electroproperties of Derivatives Based on Diphenylamine

The substituted monomers 4a , c , d, 5a , b, 6a, 7a , b , and 8a of novel poly(diphenylamines), possessing the respective photochromic groups, were synthesized by the Stille cross‐coupling methodology (Scheme). The hyperbranched structures were characterized by ¹H‐ and ¹³C‐NMR spectroscopy. The obtained monomers show good stability in common organic solvents such as CHCl₃, toluene, and CH₂Cl₂, and exhibit excellent thermal stability. Electrochemical results and theoretical calculations suggest that oxidation and reduction of the monomers start from the side of the amine function and the five‐membered heterocyclic ring moieties, respectively.     

Repetitive inductions of bioluminescence of <Emphasis Type="Italic">Pseudomonas putida</Emphasis> TVA8 immobilised by adsorption on optical fibre

Physico-chemical models of the interactions of cells with solid surfaces, which use contact angles and zeta potentials, indicated more facile adsorption of cells of Pseudomonas putida TVA8 on the quartz surface after its treatment with 3-aminopropyltriethoxysilane (APTES). A whole-cell optical fibre sensor of toluene was prepared by the adsorption of P. putida TVA8, bacteria producing light in contact with toluene on the wider end of APTES- treated quartz tapered optical fibre. The results of the measurements of luminescence from both sides of the layer of adsorbed cells were compared. Over the 135 days trial, the fibre biosensor was repetitively induced with toluene solution (26.5 mg L^?1) 68 times. The intensities of bioluminescence gradually decreased due to release of the adsorbed cells and they were only temporarily restored by the addition of nutrients. The intensities of bioluminescence induced with contaminated ground water were lower than in the mineral medium (MSM) with the same content of toluene.     

Spectrophotometric and AM1d studies of the equilibria between oxidovanadium(IV) and four isomers of n-propyl-3-azido-2,3-dideoxy-d-hexopyranosides in aqueous solution

Complex formation and stability constants for complexes between isomers of n-propyl-3-azido-2,3-dideoxy-d-hexopyranosides and oxidovanadium(IV) were determined in aqueous solution by the spectrophotometric method. Complexes of 1?:?2 metal-to-ligand stoichiometry were formed. The impact of the structures of the ligands on the complex formation was discussed. The energetically most favorable structures of the complexes were calculated and visualized by the AM1d method at the semi-empirical level of theory.     

<Superscript>47</Superscript>Sc production development by cyclotron irradiation of <Superscript>48</Superscript>Ca

The therapeutic radionuclide ⁴⁷Sc was produced through the ⁴⁸Ca(p,2n) channel on a proton beam accelerator. The obtained results show that the optimum proton energies are in the range of 24–17 MeV, giving the possibility to produce ⁴⁷Sc radionuclide containing 7.4% of ⁴⁸Sc. After activation, the powdery CaCO₃ target material was dissolved in HCl and scandium isotopes were isolated from the targets. The performed separation experiments indicate that, due to the simplicity of the operations and the chemical purity of the obtained ⁴⁷Sc the best separation process is when scandium radioisotopes are separated on the 0.2 µm filter.     

The order-disorder state of diaminoalkanes in Cu-based metal-organic materials

Two novel metal-organic compounds, [NH₃(CH₂)_nNH₃][Cu₂(HCOO)₄Cl₂], where n = 3,4, have been investigated by X-ray diffraction and spectroscopic methods to determine the interactions in the crystal and their influence on the molecular arrangement. The disorder found in the n = 3 crystal is of static nature as it has been confirmed by IR and Raman spectroscopy. It has also been suggested that the copper paddle-wheel pyramids can accommodate the conformation of the 1,3-diaminopropane cations through rotary motion.     

Visible-light-promoted alkylation of unsaturated MIDA boronates using Ru(bpy)3Cl2 as the photoredox catalyst

The development of a visible light-mediated atom transfer radical addition (ATRA) of perfluoroalkyl iodides to ethynyl-, vinyl- and allyl-MIDA boronates using the reductive and oxidative quenching of [Ru(bpy)₃]Cl₂ is described. Using an operationally simple and mild protocol, the corresponding MIDA boronates containing perfluoroalkyl groups were obtained in moderate to high yields. The structures of three products were confirmed by single crystal X-ray diffraction studies.     

Mouse thymidylate synthase does not show the inactive conformation,observed for the human enzyme

Crystal structures of mouse thymidylate synthase (mTS) in complexes with (1) sulfate anion, (2) 2′-deoxyuridine 5′-monophosphate (dUMP) and (3) 5-fluoro-dUMP (FdUMP) and N ^5,10-methylenetetrahydrofolate (meTHF) have been determined and deposited in Protein Data Bank under the accession codes 3IHI, 4E5O and 5FCT, respectively. The structures show a strong overall similarity to the corresponding structures of rat and human thymidylate synthases (rTS and hTS, respectively). Unlike with hTS, whose unliganded and liganded forms assume different conformations (“inactive” and “active,” respectively) in the loop 181–197, in each of the three mTS structures, the loop 175–191, homologous to hTS loop 181–197, populates the active conformer, with catalytic Cys 189 buried in the active site and directed toward C(6) of the pyrimidine ring of dUMP/FdUMP, pointing to protein’s inability to adopt the inactive conformation. The binary structures of either dUMP- or sulfate-bound mTS, showing the enzyme with open active site and extended C-terminus, differ from the structure of the mTS–5-FdUMP–meTHF ternary complex, with the active site closed and C-terminus folded inward, thus covering the active site cleft. Another difference pertains to the conformation of the Arg44 side chain in the active site-flanking loop 41–47, forming strong hydrogen bonds with the dUMP/FdUMP phosphate moiety in each of the two liganded mTS structures, but turning away from the active site entrance and loosing the possibility of H-bonding with sulfate in the sulfate-bound mTS structure.     

Towards tuning PDT relevant photosensitizer properties: comparative study for the free and Zn2+ coordinated meso-tetrakis[2,6-difluoro-5-(N-methylsulfamylo)phenyl]porphyrin

The spectroscopic, photochemical, and biological studies of 5,10,15,20-tetrakis[2,6-difluoro-5(N-methylsulfamylo)phenyl]porphyrinate Zn(II) (ZnF₂PMet) were carried out including absorption and fluorescence spectra, fluorescence quantum yields, triplet absorption spectra, triplet lifetimes, singlet oxygen quantum yield, and reactive oxygen species (ROS) detection under biological conditions and compared with its free-base analog (F₂PMet). Zinc coordination into the porphyrin ring results in decrease of hydrophobicity and in higher cellular uptake. F₂PMet localized specifically in endoplasmic reticulum and mitochondria while the ZnF₂PMet is more diffused all over the cell, bonded to membrane proteins, as assessed by fluorescence microscopy. Zn-porphyrin exhibits greater singlet oxygen quantum yield than its free-base analog. Studies with fluorescent probes confirm that the ZnF₂PMet produces mostly singlet oxygen, whereas F₂PMet generates more hydroxyl radicals as the ROS. F₂PMet is a more effective photosensitizer in vitro than its zinc complex, thus, the final photodynamic effect depends more on the nature of ROS than on the higher cellular uptake.     

1H and 13C NMR Analysis of Poly(succinimide) Prepared by Microwave-Enhanced Polycondensation of L-Aspartic Acid

Poly(succinimide) (PSI) is a polymer of aspartic acid with interesting properties and numerous possible uses. Application areas include agriculture, cleaning agents, metallurgy, the building industry, wastewater treatment, medicine, pharmaceuticals, bioengineering, and many more. Therefore, the particular structure analysis is crucial for these purposes, especially considering possible reactions between monomer and solvent used in the polycondensation process. Moreover, utilization of microwave irradiation in such synthesis is conducive to reducing reaction time and improving yield. In this article, the detailed structure analysis of PSI prepared under microwave irradiation conditions as well as a comparison study with thermally synthesized PSI are presented.