Reduced-dimensionality quantum bound state treatment of hydrogen-bonded clusters: torsional vibrational manifold of the water trimer

A review of our reduced-dimensionality quantum dynamical treatments of the coupled low-frequency large-amplitude torsional vibrations of the water trimer is presented. It covers three-dimensional bound state calculations of the intermolecular torsional energy levels of (H₂O)₃, (D₂O)₃, and other isotopomers, and quantum (3+1)-dimensional torsional-stretching calculations of torsional-state dependent vibrationally averaged rotational constants of isotopically pure and mixed water trimers.     

13C and 1H n.m.r. study of the polyesterification of maleic anhydride and 1,2-propylene glycol

The reaction steps of the polyesterification of maleic anhydride and 1,2-propylene glycol were followed by ¹³C and ¹H n.m.r. spectroscopy. The number and structure of mono- and diesters of both maleates and fumarates in the reaction mixture are determined by the possible glycol unit configurations. The structure of the growing polyester chain reflects a statistical distribution of approximately equal numbers of symmetric and asymmetric arrangements of the polymer sequences.     

New Insights into the Setting Processes of Glass Ionomer Cements from Analysis of Dielectric Properties

The setting processes in the commercial glass ionomer cement (Fuji IX Fast) and resin modified glass ionomer cement (Fuji II LC) were investigated by the dielectric spectroscopy. The changes in the real and imaginary parts of the dielectric permittivity [ε*(ω)] as well as dielectric loss (tan δ) with time for Fuji IX Fast show several distinct regions which are related to the different stages of the acid–base reaction. Interestingly, the first stage that lasts for approximately 12 min terminates with a sharp decrease in dielectric parameters which is most probably related to the instantaneous (micro)fracturing of the sample due to a rapid build–up of the shrinkage stress. On the other hand, evolution of the dielectric properties during the setting of Fuji II LC indicates fast reaction in the initial stage (within few minutes) followed by the slow gradual change as a result of the competing nature of the acid–base reaction and light‐activated polymerization.     

Changes of properties of cured and uncured disiloxane bisbenzocyclobutene thin films under irradiation

The effects induced by α-particles and laser beam irradiation in air atmosphere in uncured and cured bisbenzocyclobutene (BCB) 2 μm thick films, spin-coated on glass/ITO surface have been investigated. α-Particle irradiation was done by means of a thin film ²⁴¹Am source (E_α = 5.486 MeV), up to the total fluence of about 5 × 10¹⁰ particles/cm². Laser irradiation was performed by a Nd³⁺:YAG (λ = 1.06 μm) laser in the free generation and the Q-switch regime, using both focused and unfocused beams. Irradiation induced changes were investigated using Light and Atomic Force Microscopy (AFM), infrared (IR), Ultraviolet/visible (UV/vis) and Raman spectroscopy by inspecting several uncured and cured BCB films before and after irradiation. It has been found that both types of irradiation under investigated conditions have produced a novel phase in the material, which is not present either in the uncured or the cured BCB films. Possible implications of the observed effects on curing and degradation of BCB films have been discussed.     

Effectiveness of ozonation treatment in eliminating toxicity of oil sands process-affected water to Chironomus dilutus

Water soluble organic compounds (OCs), including naphthenic acids (NAs), are potentially toxic constituents of oil sands process-affected water (OSPW) that is generated during extraction of bitumen from Alberta oil sands. Ozonation can decrease concentrations of OCs in OSPW. However, effects of ozonated-OSPW on multicellular organisms are unknown. A 10-day and a chronic exposure of Chironomus dilutus to OSPW were conducted to assess effects on survival, growth, development, and behavior. Two separate batches of OSPW were treated with 30 or 80 mg ozone (O(3))/L. Wet body masses of larvae exposed to OSPW were 64 to 77% less than their respective controls (p < 0.001). However, both levels of ozonation significantly attenuated effects of OSPW on growth. Similarly, chronic exposure to untreated OSPW resulted in significantly less pupation than in the controls, with 31% and 71% less pupation of larvae exposed to the two batches of OSPW (p < 0.05). Emergence was significantly less for larvae exposed to OSPW, with 13% and 8% of larvae emerging, compared to 81% in controls (p < 0.0001). Both levels of ozonation of OSPW attenuated effects on emergence. These results suggest that OCs degraded by ozonation causes toxicity of OSPW toward C. dilutus, and that ozonation attenuates toxicity of OSPW.     

Design and Synthesis of Fluorescent Acyclic Nucleoside Phosphonates as Potent Inhibitors of Bacterial Adenylate Cyclases

Bordetella pertussis adenylate cyclase toxin (ACT) and Bacillus anthracis edema factor (EF) are key virulence factors with adenylate cyclase (AC) activity that substantially contribute to the pathogenesis of whooping cough and anthrax, respectively. There is an urgent need to develop potent and selective inhibitors of bacterial ACs with prospects for the development of potential antibacterial therapeutics and to study their molecular interactions with the target enzymes. Novel fluorescent 5‐chloroanthraniloyl‐substituted acyclic nucleoside phosphonates (Cl‐ANT‐ANPs) were designed and synthesized in the form of their diphosphates (Cl‐ANT‐ANPpp) as competitive ACT and EF inhibitors with sub‐micromolar potency (IC₅₀ values: 11–622 nm ). Fluorescence experiments indicated that Cl‐ANT‐ANPpp analogues bind to the ACT active site, and docking studies suggested that the Cl‐ANT group interacts with Phe306 and Leu60. Interestingly, the increase in direct fluorescence with Cl‐ANT‐ANPpp having an ester linker was strictly calmodulin (CaM)‐dependent, whereas Cl‐ANT‐ANPpp analogues with an amide linker, upon binding to ACT, increased the fluorescence even in the absence of CaM. Such a dependence of binding on structural modification could be exploited in the future design of potent inhibitors of bacterial ACs. Furthermore, one Cl‐ANT‐ANP in the form of a bisamidate prodrug was able to inhibit B. pertussis ACT activity in macrophage cells with IC₅₀=12 μm .