Measuring the pollutant transport capacity of dissolved organic matter in complex matrixes

Dissolved organic matter (DOM) facilitated transport in contaminated groundwater was investigated through the measurement of the binding capacity of landfill leachate DOM (Vejen, Denmark) towards two model pollutants (pyrene and phenanthrene). Three different methods for measuring binding capacity were used and evaluated, head-space solid-phase micro-extraction (HS-SPME), enhanced solubility (ES) and fluorescence quenching (FQ). It was concluded that for samples with complex matrixes it was possible to measure the net effect of the DOM binding capacity and the salting out effect of the matrix. It was further concluded that DOM facilitated transport should be taken into account for non-ionic PAHs with lg?K?_OW above 5, at DOM concentrations above 250?mg?C/L. The total DOM concentration was found to be more important for the potential of facilitated transport than differences in the DOM binding capacity.     

Photoionization study of Hg2

Photoionization efficiency data for Hg₂⁺ have been obtained in the region of 650–1400 A. The ionization energy of Hg₂ was determined to be 9.103 ± 0.010 eV. This value allows the calculation of the dissociation energy of Hg⁺₂ to be 1.40 ± 0.02 eV. By analyzing the differences in energy between corresponding autoionization peaks observed in the Hg⁺ and the Hg₂⁺ spectra and by assuming the charge induced-dipole interaction to be the dominant interaction between Hg⁺(²D_{5/2, 3/2}) and Hg at the equilibrium bond distance of Hg₂, the equilibrium bond distance for Hg₂ was deduced to 3.35 A.     

Synthesis and anticonvulsant activity of 1-benzyl-4-alkylamino-1H-imidazo[4,5-c]pyridines

Four 3-deaza analogues of the potent anticonvulsant purine, BW A78U, were synthesized and tested for anticonvulsant activity. The imidazo[4,5-c]pyridines 9–12 were prepared in two steps from 4-chloro-1H-imidazo[4,5-c]pyridine ( 2 ). The compounds were potent anticonvulsant agents against maximal electroshock-induced seizures in rats with i.p. ED₅₀ ranging from 2 to 3.5 mg/kg. However, these 3-deazapurines were appreciably more toxic than BW A78U, which precluded their development as potential antiepileptic agents.     

IN VIVO EXCISION OF PYRIMIDINE DIMERS IS MEDIATED BY A DNA N-GLYCOSYLASE IN MICROCOCCUS LUTEUS BUT NOT IN HUMAN FIBROBLASTS

Abstract It has been previously shown that Micrococcus luteus possesses a pyrimidine dimer-specific endonuclease which in vitro , functions as both an endonuclease and DNA-glycosylase. To determine if these combined activities function in vivo , we have isolated and examined the excision products of UV-irradiated M. luteus . In addition, we have devised a procedure to isolate and examine the excision products from UV-irradiated human fibroblasts to determine if an endonuclease/glycosylase activity functions in the excision of UV-induced pyrimidine dimers in human fibroblasts. We find that, in vivo , an endonuclease/glycosylase mechanism is utilized extensively in the repair of pyrimidine dimers by M. luteus , but that human fibroblasts do not appear to use this mechanism.     

New synthetic approaches to estrogen receptor modulators: imidazo[1,2-a]pyridines

Constrained triarenes have been important templates for selective modulation of the estrogen receptor (ER). For our ER program, we sought an unexplored, synthetically accessible heterocyclic template capable of bearing a broad range of pharmacophores. Traditional approaches to these therapeutics such as raloxifene have relied on an alkoxy moiety to link the arene-based scaffold to the modulating amine group. Alternatively, aryl halide-mediated introduction of alkylene or aryl side chains has not been studied extensively. The synthetic incorporation of pharmacophoric side chains that are carbon-linked to a novel imidazopyridine-based ER recognition motif is disclosed.     

Novel norcassane-type diterpene from the seed kernels of Caesalpinia crista

Three novel norcassane-type diterpenes were isolated from a CH₂Cl₂ extract of the seed kernels of Caesalpinia crista together with four known cassane-type diterpenes. All the new compounds represent unprecedented carbon framework. Norcaesalpinin A (1) and B (2) had 17-norcassane skeleton, while norcaesalpinin C (3) had 16-norcassane skeleton. Their structures were elucidated on the basis of spectral analysis.     

Position of coordination of the lithium ion determines the regioselectivity of demethylations of 3,4-dimethoxymorphinans with L-selectride

[reaction: see text] L-Selectride is an efficient agent for the 3-O-demethylation of opioids and is known to cleave the least hindered methoxyl group in a molecule. The treatment of a 3,4-dimethoxymorphinan containing a 6-ketal with L-Selectride gave selective 4-O-demethylation, rather than cleavage of the less hindered 3-methoxyl. In contrast, a 3,4-dimethoxymorphinan lacking a 6-ketal gave selective 3-O-demethylation, suggesting that the regiochemistry of L-Selectride-mediated O-demethylation can be manipulated through altering the position of coordination of the lithium ion.     

Effect of pectin extraction method on properties of cellulose nanofibers isolated from sugar beet pulp

In this study, the effect of pectin extraction method on the properties of cellulose nanofibers (CNFs) isolated from sugar beet pulp (SBP) was studied. Pectin was extracted by the industrially practiced method by sulfuric acid hydrolysis or by enzymatic hydrolysis using a cellulase/xylanase enzymes mixture. The CNFs were then isolated by high-pressure homogenization and investigated in terms of their chemical composition, crystallinity, size, degree of polymerization, and re-dispersion in water after freeze-drying. The mechanical properties and surface characteristics of CNF films were also studied. The results showed that fibrillation of the de-pectinated SBP was more efficient for the acid hydrolyzed SBP. CNFs from the acid-hydrolyzed SBP had a slightly wider diameter, higher crystallinity, viscosity, and α-cellulose content but a lower degree of polymerization than CNFs from the enzyme-hydrolyzed SBP. Owing to the presence of more residual hemicelluloses in the CNFs from the enzyme-hydrolyzed SBP, the CNFs had higher re-dispersion ability in water. CNF films from enzyme-hydrolyzed SBP displayed slightly better mechanical properties and higher water contact angle than acid-hydrolyzed CNF films.

Graphic abstract

     

(S)-selective kinetic resolution and chemoenzymatic dynamic kinetic resolution of secondary alcohols

(S)-Selective kinetic resolution was achieved through the use of a commercially available protease, which was activated with a combination of two different surfactants. The kinetic resolution (KR) process was optimized with respect to activation of the protease and to the acyl donor. The KR proved to be compatible with a range of functionalized sec-alcohols, giving good to high enantiomeric ratio values (up to >200). The enzymatic resolution was combined with a ruthenium-catalyzed racemization to give an (S)-selective dynamic kinetic resolution (DKR) of sec-alcohols. The DKR process works under very mild reaction conditions to give the corresponding esters in high yields and with excellent enantioselectivities.