Photoinduced Formation of Reactive Oxygen Species from the Acid Form of 6‐(Hydroxymethyl)pterin in Aqueous Solution

The photochemistry of 6‐(hydroxymethyl)pterin (HPT; 1 ) in aqueous solution (pH 5–6) was investigated by irradiation at 350 nm at room temperature. The photochemical reactions of the acidic form 1a were followed by UV/VIS spectrophotometry, thin‐layer chromatography (TLC), high‐performance liquid chromatography (HPLC), and enzymatic methods for the determination of the superoxide anion radical (O ) and hydrogen peroxide (H₂O₂). When 1a is exposed to UV‐A radiation, the intermediates 4 and 4′ are formed reacting with O₂ to yield 6‐formylpterin (FPT; 5 ) and 6‐carboxypterin (CPT; 6 ) under formation of O and H₂O₂ (Scheme 3). The quantum yields of the disappearance of HPT ( 1a ) and of the formation of the photoproducts 5 and 6 were determined. HPT was investigated for its efficiency in singlet‐oxygen (¹O₂) production in acidic aqueous solution. The corresponding quantum yield of ¹O₂ production (Φ_Δ) was 0.15 ± 0.02, as measured by the ¹O₂ luminescence in the near‐IR (1270 nm) upon continuous excitation of the sensitizer. However, ¹O₂ does not participate in the actual photooxidation of HPT ( 1a ) to FPT ( 5 ) and CPT ( 6 ).     

Syntheses, structures, physical properties, and theoretical studies of CeMxOS (M = Cu, Ag; x approximately 0.8) and CeAgOS

Black single crystals of the two nonstoichiometric cerium coinage-metal oxysulfide compounds CeCu(x)OS and CeAg(x)OS (x approximately 0.8) have been prepared by the reactions of Ce2S3 and CuO or Ag2O at 1223 or 1173 K, respectively. A black powder sample of CeAgOS has been prepared by the stoichiometric reaction of Ce2S3, CeO2, Ag2S, and Ag at 1073 K. These isostructural materials crystallize in the ZrSiCuAs structure type with two formula units in the tetragonal space group P4/nmm. Refined crystal structure results and chemical analyses provide evidence that the previously known anomalously small unit-cell volume of LnCuOS for Ln = Ce (Ln = rare-earth metal) is the result of Cu vacancies and the concomitant presence of both Ce3+ and Ce4+. Both CeCu(0.8)OS and CeAgOS are paramagnetic with mu(eff) values of 2.13(6) and 2.10(1) mu(B), respectively. CeCu(0.8)OS is a p-type semiconductor with a thermal activation energy Ea = 0.22 eV, sigma(electrical) = 9.8(1) 10(-3) S/cm at 298 K, and an optical band gap Eg < 0.73 eV. CeAgOS has conductivity sigma(conductivity) = 0.16(4) S/cm and an optical band gap Eg = 0.71 eV at 298 K. Theoretical calculations with an on-site Coulomb repulsion parameter indicate that the Ce 4f states are fully spin-polarized and are not localized in CeCuOS, CeCu(0.75)OS, or CeAgOS. Calculated band gaps for CeCu(0.75)OS and CeAgOS are 0.6 and 0.8 eV, respectively.     

Syntheses, characterization, and X-ray crystal structures of beta-diketiminate group 13 hydrides, chlorides, and fluorides

A series of organometallic compounds of group 13 metals supported by the sterically encumbered beta-diketiminate ligand containing hydrides, fluorides, chlorides, and bromide have been synthesized and structurally characterized. The synthetic strategy applied utilizes halide metathesis and reduction of metal chlorides to the corresponding hydrides. Thus, the reaction of LLi.OEt2 with MeMCl2 affords LM(Me)Cl (M = Al (1), Ga (2), In (3)) and LGaBr2 (4) with GaBr3. Reduction of LGa(Me)Cl with LiH.BEt3 leads to the formation of LGa(Me)H (10). Synthesis of LGaH(2) (12) has been accomplished by reacting LGaI2 (8) with LiH.BEt3. LAl(Me)Cl (1) and LAlH2 (6) have been converted to LAl(Me)F (5) and LAlF2 (7), respectively. The former was obtained in a reaction of LAl(Me)Cl with Me3SnF while the latter was isolated in a reaction of LAlH2 with BF3.OEt2. Similarly reaction of LGaI2 (8) with Me3SnF affords LGaF2 (9). Compounds reported herein have been characterized by elemental analyses, IR, NMR, EI-MS, and single-crystal X-ray diffraction techniques.     

Monitoring virus-like particle and viral protein production by intact cell MALDI-TOF mass spectrometry

A new application of intact cell MALDI-TOF MS (ICM-MS) methodology is described for monitoring the production of viral proteins and viral like particles using the baculovirus/insect cells expression system. Various MALDI matrices, cell preparation methods, cell/matrix volume ratio and MALDI target application procedures were tested in order to obtain the highest intensity and reproducibility of intact insect cell spectra. The web interface, SPECLUST (http://bioinfo.thep.lu.se/speclust.html), was used to construct dendograms based on MALDI-TOF MS data for evaluation of fingerprint changes.We demonstrate that insect cell mass spectrum fingerprints are characteristic of each viral protein/particle production. Their changes along the time for each production experiment correlate with the intracellular viral protein content determined by Western blot.This work shows that this simple, fast and low cost assay, which requires low sample volume, is a powerful analytical tool that complements the most common analytical methods used for monitoring bioprocesses and has potential application in the biotechnological industry namely, in the production of recombinant proteins.     

Versatile microanalytical system with porous polypropylene capillary membrane for calibration gas generation and trace gaseous pollutants sampling applied to the analysis of formaldehyde, formic acid, acetic acid and ammonia in outdoor air

The analytical determination of atmospheric pollutants still presents challenges due to the low-level concentrations (frequently in the μg m⁻³ range) and their variations with sampling site and time. In this work, a capillary membrane diffusion scrubber (CMDS) was scaled down to match with capillary electrophoresis (CE), a quick separation technique that requires nothing more than some nanoliters of sample and, when combined with capacitively coupled contactless conductometric detection (C⁴D), is particularly favorable for ionic species that do not absorb in the UV-vis region, like the target analytes formaldehyde, formic acid, acetic acid and ammonium. The CMDS was coaxially assembled inside a PTFE tube and fed with acceptor phase (deionized water for species with a high Henry's constant such as formaldehyde and carboxylic acids, or acidic solution for ammonia sampling with equilibrium displacement to the non-volatile ammonium ion) at a low flow rate (8.3 nL s⁻¹), while the sample was aspirated through the annular gap of the concentric tubes at 2.5 mL s⁻¹. A second unit, in all similar to the CMDS, was operated as a capillary membrane diffusion emitter (CMDE), generating a gas flow with know concentrations of ammonia for the evaluation of the CMDS. The fluids of the system were driven with inexpensive aquarium air pumps, and the collected samples were stored in vials cooled by a Peltier element. Complete protocols were developed for the analysis, in air, of NH₃, CH₃COOH, HCOOH and, with a derivatization setup, CH₂O, by associating the CMDS collection with the determination by CE-C⁴D. The ammonia concentrations obtained by electrophoresis were checked against the reference spectrophotometric method based on Berthelot's reaction. Sensitivity enhancements of this reference method were achieved by using a modified Berthelot reaction, solenoid micro-pumps for liquid propulsion and a long optical path cell based on a liquid core waveguide (LCW). All techniques and methods of this work are in line with the green analytical chemistry trends.     

Speciation of nickel by HPLC-UV/MS in pea nodules

A new and sensitive methodology based on normal phase HPLC has been developed for the speciation of nickel in low-complexity plant extracts. The method combines a silica stationary phase column, a 9:1 (v/v) hexane:ethanol mixture as mobile phase, and the detection of nickel complexes by either UV or MS. The developed methodology was applied to the speciation of nickel complexes in the cytoplasm of pea root nodules. Results obtained indicate that nickel citrate and nickel malate accounts for 99% of nickel present in pea nodule cytoplasm fraction. The low detection limit of the method (<0.2 nM) enables nickel speciation in non-hyperaccumulator plants.     

Antibacterial mono- and sesquiterpene esters of benzoic acids from Iranian propolis

Background  

Propolis (bee glue) has been used as a remedy since ancient times. Propolis from unexplored regions attracts the attention of scientists in the search for new bioactive molecules.     

A secretome-based methodology may provide a better characterization of the virulence of Listeria monocytogenes: preliminary results

Four strains of Listeria monocytogenes with different levels of virulence were studied. Two strains were consistently evaluated as virulent (strain 3077) and of low virulence (strain 3993), whereas the other two strains (3006 and 3049) originated conflicting results in what the evaluation tests were concerned: both were shown to exhibit low virulence when evaluated by in vitro assays, but virulent when the analyses were performed under in vivo conditions.To clarify the virulence potential of the selected strains, a proteomic approach was used after incubating L. monocytogenes cultures under conditions favoring the expression of virulence factors (minimal medium, at 37 °C). Bacterial proteins present in the liquid culture media were precipitated from late exponential phase cultures, fractionated by SDS-PAGE and identified by MALDI-TOF-MS.Three virulence factors differentially expressed were detected: protein p60, listeriolysin O (LLO) and internalin C (InlC). Clustering analysis of the four L. monocytogenes strains based on their secretome profiles allowed their categorization in two groups: the virulent group, composed by strains 3077 and 3049, and the low virulence group, containing strains 3993 and 3006. The results presented in this work suggest that the virulent potential of a particular L. monocytogenes strain may be predicted from the levels of both listeriolysin O (LLO) and internalin C (InlC) present in its secretome when the bacterium is grown under conditions favoring the expression of virulence factors. Following validation of this proposal through the analysis of a large array of strains, this methodology exhibits a great potential to be developed into an accurate and rapid method to characterize L. monocytogenes strain virulence.     

Straightforward entry to libraries of diversely substituted azinones by a consecutive aza-Michael/palladium-catalyzed functionalization strategy

A highly divergent, flexible, and conceptually simple sequence allowing the parallel solution-phase assembly of functionalized azinone libraries has been developed in a one-pot consecutive fashion. Structural decoration of in situ-generated heterocyclic aza-Michael adducts AB was accomplished by exploiting the diversity potential of Heck, Suzuki, Sonogashira, and Stille reactions.