A unique bacteriohopanetetrol stereoisomer of marine anammox

Anaerobic ammonium oxidation (anammox) is a major process of bioavailable nitrogen removal from marine systems. Previously, a bacteriohopanetetrol (BHT) isomer, with unknown stereochemistry, eluting later than BHT using high performance liquid chromatography (HPLC), was detected in ‘Ca. Scalindua profunda’ and proposed as a biomarker for anammox in marine paleo-environments. However, the utility of this BHT isomer as an anammox biomarker is hindered by the fact that four other, non-anammox bacteria are also known to produce a late-eluting BHT stereoisomer. The stereochemistry in Acetobacter pasteurianus, Komagataeibacter xylinus and Frankia sp. was known to be 17β, 21β(H), 22R, 32R, 33R, 34R (BHT-34R). The stereochemistry of the late-eluting BHT in Methylocella palustris was unknown. To determine if marine anammox bacteria produce a unique BHT isomer, we studied the BHT distributions and stereochemistry of known BHT isomer producers and of previously unscreened marine (‘Ca. Scalindua brodeae’) and freshwater (‘Ca. Brocadia sp.’) anammox bacteria using HPLC and gas chromatographic (GC) analysis of acetylated BHTs and ultra high performance liquid chromatography (UHPLC)-high resolution mass spectrometry (HRMS) analysis of non-acetylated BHTs. The 34R stereochemistry was confirmed for the BHT isomers in Ca. Brocadia sp. and Methylocella palustris. However, ‘Ca. Scalindua sp.’ synthesise a stereochemically distinct BHT isomer, with still unconfirmed stereochemistry (BHT-x). Only GC analysis of acetylated BHT and UHPLC analysis of non-acetylated BHT distinguished between late-eluting BHT isomers. Acetylated BHT-x and BHT-34R co-elute by HPLC. As BHT-x is currently only known to be produced by ‘Ca. Scalindua spp.’, it may be a biomarker for marine anammox

A dried blood spot assay for paclitaxel and its metabolites

After being used for decades in clinical screening, dried blood spots (DBS) have recently received considerable attention for their application in pharmacokinetic and toxicokinetic studies in rodents. The goal of this study was to develop and apply a DBS-based assay for a pharmacokinetic study of paclitaxel (PTX) and its metabolites in SCID/Beige mice. A fast and sensitive UHPLC-MS/MS method has been developed for the simultaneous determination of PTX, its three metabolites (6 alpha-hydroxy-paclitaxel, 3'-p-hydroxypacli taxel, and 6a,3'-p-dihydroxy-paclitaxel) and its stereoisomer 7-epi-p aclitaxel. The 10 mu L DBS sample was extracted with methanol for 20 min at 37 degrees C. After dilution of the extracts with water in a ratio of 1:1, the analytes were separated on a reversed-phase 2.1 mm I.D. column using gradient elution. The total run time was 2.5 min. The analytes were detected by use of multiple reaction monitoring mass spectrometry. The extraction recoveries of the compounds were all greater than 60%, resulting in a quantification limit of 1 ng/ml. The calibration curves ranged from 1 to 1000 ng/ml. The intra-day and inter-day imprecision (%CV) across three validation runs over four quality control levels were less than or equal to 14.6%. The accuracy was within +/-11.9% in terms of relative error. The described method is advantageous in terms of its ease-of-use and speed compared to other published PTX assays. The method's usefulness was demonstrated by applying it to a preclinical pharmacokinetic investigation of PTX and its metabolites in SCID/Beige mice with an intraperitoneal administration of 50 mg/kg Abraxane (R)

Isolation and identification of a male-produced aggregation-sex pheromone for the velvet longhorned beetle, Trichoferus campestris.

The velvet longhorned beetle, Trichoferus campestris (Faldermann) ("VLB"; Coleoptera: Cerambycidae), is native to eastern Asia where it infests and damages a wide range of deciduous and coniferous tree species, including orchard and timber species. Immature stages of VLB are transported to new countries via international commerce, and populations have established outside the native range of the species. Here, we show that identification of pheromones of invasive pest species can be expedited by knowledge of the semiochemistry of related taxa. Histological sectioning revealed subcuticular, male-specific prothoracic glands connected to pits in the cuticle, which, in related species, are diagnostic for production of male-produced aggregation-sex pheromones, usually characterized by 2,3-alkanediol/hydroxyketone structural motifs. However, in preliminary field bioassays, beetles were not attracted by any known cerambycid pheromones. Subsequently, we identified a novel variant of the hydroxyketone motif ("trichoferone") from headspace volatiles of males. In field bioassays, synthetic trichoferone was more attractive to both sexes of VLB than previously developed high-release-rate ethanol lures, and attraction was strongly female biased. This study demonstrated the utility of the prothoracic gland trait for predicting pheromone use in cerambycid species in the subfamily Cerambycinae, and that identification of pheromones of novel species can be expedited by knowledge of pheromones of related species. Trichoferone should prove to be a valuable tool for detection of VLB in regions where the beetle is or may become established

Exploring Conditions for the Enhancement of Acene Semiconductors Through the Use of the Diels-Alder Reaction

This dissertation demonstrates the application of SAMs to the surface of acene crystals, specifically of tetracene and rubrene, using the Diels-Alder reaction. The second chapter details preliminary reaction results and two analytical methods which were employed to confirm adsorption of the dienophile on the surface of single crystals, tetracene and rubrene. These were mass spectrometry and X-ray photoelectron spectroscopy (XPS). Mass spectrometry experiments distinguish the chemical identity of adduct on the crystals and also it discerned chemi- and physisorbed molecules from one another. XPS was used to prove face selectivity of the reaction by the detection of dichloromaleic anhydride. From a mechanistic standpoint, this system demonstrated unusual steric effects: the reaction of one face of the tetracene crystal was virtually inert, while another face was facile. The dienophiles’ steric bulk was also expected to play critical role for these confined systems, however analysis of surface data was hindered by the relative lack of corresponding solution kinetic data. While the rate of anthracene’s reaction has been studied extensively with a range of dienophiles and tetracene/pentacene has been studied theoretically (with limited experimental reports), an expansive report was generated to aid in future interpretations of acene systems. These kinetic results constitute chapter three

Molecular modeling studies, synthesis, configurational stability and biological activity of 8-chloro-2,3,5,6-tetrahydro-3,6-dimethyl-pyrrolo[1,2,3-de]-1,2,4-benzothiadiazine 1,1-dioxide

The potential therapeutic benefit of compounds able to activate AMPA receptors (AMPArs) has led to a search for new AMPAr positive modulators. Among them, 8-chloro-2,3,5,6-tetrahydro-3,6-dimethyl-pyrrolo[1,2,3-de]-1,2,4-benzothiadiazine 1,1-dioxide (1) has attracted particular attention, because it is one of the most active benzothiadiazine\u2013derived positive modulators of the AMPA receptor. It possesses two stereogenic centers, C3 and C6, thus it can exist as four stereoisomers. In this work, preliminary in silico studies suggested that 1 interacts stereoselectively with AMPArs. Single stereoisomers of 1 were prepared in order to evaluate their biological activity. However, studies regarding the configurational stability of the investigated compounds suggested a rapid epimerization at C3 in aqueous solvents, and we can expect the same reaction in vivo. Thus, electrophysiological experiments were performed on the two epimeric mixtures, (3 17,6R)- and (3 17,6S)- 8-chloro-2,3,5,6-tetrahydro-3,6-dimethyl-pyrrolo[1,2,3-de]-1,2,4-benzothiadiazine 1,1-dioxide, in order to evaluate their activities as positive allosteric modulators of AMPArs. The obtained data suggest that the (3 17,6S) epimeric mixture is the most active in positively modulating AMPArs, confirming in silico results

Loss of Propiconazole and Its Four Stereoisomers from the Water Phase of Two Soil-Water Slurries as Measured by Capillary Electrophoresis

Propiconazole is a chiral fungicide used in agriculture for control of many fungal diseases on a variety of crops. This use provides opportunities for pollution of soil and, subsequently, groundwater. The rate of loss of propiconazole from the water phase of two different soil-water slurries spiked with the fungicide at 50 mg/L was followed under aerobic conditions over five months; the t1/2 was 45 and 51 days for the two soil slurries. To accurately assess environmental and human risk, it is necessary to analyze the separate stereoisomers of chiral pollutants, because it is known that for most such pollutants, both biotransformation and toxicity are likely to be stereoselective. Micellar electrokinetic chromatography (MEKC), the mode of capillary electrophoresis used for analysis of neutral chemicals, was used for analysis of the four propiconazole stereoisomers with time in the water phase of the slurries. MEKC resulted in baseline separation of all stereoisomers, while GC-MS using a chiral column gave only partial separation. The four stereoisomers of propiconazole were lost from the aqueous phase of the slurries at experimentally equivalent rates, i.e., there was very little, if any, stereoselectivity. No loss of propiconazole was observed from the autoclaved controls of either soil, indicating that the loss from active samples was most likely caused by aerobic biotansformation, with a possible contribution by sorption to the non-autoclaved active soils. MEKC is a powerful tool for separation of stereoisomers and can be used to study the fate and transformation kinetics of chiral pesticides in water and soil

New Strategies in Regio- and Stereoselective Synthesis by the use of Small-Medium Ring Heterocycles

In questo lavoro di tesi viene riportato un ampio studio circa il comportamento di una gamma di eterocicli nelle reazioni di apertura con nucleofili ossigenati e al carbonio

Complex formation and enantioselectivity studies of triazole fungicide and organophosphorus pesticide enantiomers using capillary electrophoresis

Several cyclodextrin modified-micellar electrokinetic chromatography (CDMEKC) methods were developed for the successful triazole fungicides separation. In the first part, an efficient method was developed for the simultaneous enantioseparation of cyproconazole (4 stereoisomer), bromuconazole (4 stereoisomer) and diniconazole (2 stereisomer) enantiomers using CD-MEKC with a dual mixture of neutral cyclodextrins as chiral selector. The best simultaneous separation of cyproconazole, bromuconazole, and diniconazole enantiomers was achieved with a mixture of 27 mM HP-β-CD and 3 mM HP-γ-CD in 25 mM phosphate buffer (pH 3.0) containing 40 mM sodium dodecyl sulfate (SDS) and 15% iso-propanol as organic modifier. Complete separation of 10 stereoisomer of triazole fungicides were obtained in a single run with good resolution (Rs 1.74“26.31) and high peak efficiency (N > 400 000). In the second part of the study, enantioseparation of hexaconazole, penconazole, myclobutanil, and triadimefon was investigated. Simultaneous enantioseparation of penconazole, myclobutanil, and triadimefon was achieved under acidic condition (pH 3.0) using 25 mM phosphate buffer, 50 mM SDS, and 30 mM HP-γ-CD, with Rs greater than 0.9 whereas, simultaneous enantioseparation of hexaconazole, penconazole, and myclobutanil was successfully achieved under neutral condition (pH 7.0) using 25 mM phosphate buffer, 40 mM SDS, and 40 mM HP-γ-CD, with Rs greater than1.6. In order to improve detection sensitivity, on-line preconcentration technique was investigated. It was found that sweeping technique as an on-line preconcentration technique improved the detection sensitivity of the enantioseparation of cyproconazole, bromuconazole, and diniconazole by 30 to 60-fold, with good repeatabilities in the migration time, peak area and peak height were obtained with RSDs in the range of 0.08“0.32%, 0.03“ 2.44%, and 2.13“8.44% respectively. Furthermore, sweeping technique improved the detection sensitivity of the enantioseparation of hexaconazole, penconazole and myclobutanil by 62- to 67-fold. Good repeatabilities in the migration time, peak area and peak height were obtained with RSDs in the range of 2.39“3.90%, 1.96€“6.15%, and 2.80“6.64% respectively. Finally, the formation constant of diniconazole enantiomers with HP-γ-CD under neutral and acidic condition was investigated using CD-MEKC

Design, synthesis and binding studies of calix(4)pyrrole based receptors suitable for ion-pair complexation and n-oxide recognition. Synthesis of resorcin(4) arene derivatives as potential ligands for supramolecular catalysis

El trabajo de tesis doctoral ha consistido en el diseño y síntesis de diferentes receptores moleculares. En particular, de nuevos derivados calix[4]pirrolaril-extendidos con dos y cuatro grupos fosfonatocomo receptores ditópicos para la complejación de pares iónicos,importantes para la extracción de sales y para el transporte de iones a través de las membranas celulares. Asimismo, derivados de calix[4]pirrol han sido preparados para la inclusión de N-óxidos en conformación de alta energía.La importancia de la inclusiónha sido demostrada en la modificación dela reactividad químicatípica delN-óxidoenreacciones en las queel mismo seutilizacomo co-oxidante. Porúltimo, se presentan derivados de resorcin[4]areno con grupos etilo en la parte inferior y una pared móvil en la parte superior como potenciales ligandos para catálisis supramolecular.The work developed during the PhD thesis deals mainly with the design and synthesis ofSupramolecular Hosts. In particular, we present new aryl-extended calix[4]pyrroleswith two or four phosphonate groups as heteroditopic receptors for the complexation of ion-pairs and that result important for the extraction of salts and for the transportof ions through membranes. Likewise, derivativesofcalix[4]pyrroles have been prepared for the selective inclusionofN-oxides in high energy conformation.The importance of the inclusion has been demonstrated by the change of the reactivity of the N-oxide in reactions in which it is commonly used as co-catalyst. Finally, we present derivatives ofresorcin[4]arenes with ethyl groups at the lower rim of thereceptor and a mobile wall in the upper rim as potential ligands for Supramolecular catalysis