Synthesis, Structure, and Phosphatase-Like Activity of a New Trinuclear Gd Complex with the Unsymmetrical Ligand H(3)L As a Model for Nucleases

The new trinuclear gadolinium complex [Gd(3)L(2)(NO(3))(2)(H(2)O)(4)]NO(3)center dot 8H(2)O (1) with the unsymmetrical ligand 2-[N-bis-(2-pyridylmethyl)aminomethyl]-4-methyl-6-[N-bis(2-hydroxy-2-oxoethyl)aminomethyl] phenol (H(3)L) was synthesized and characterized. The new ligand H(3)L was obtained in good yield. Complex I crystallizes in an orthorhombic cell, space group Pcab. Kinetic studies show that complex 1 is highly active in the hydrolysis of the substrate 2,4-bis(dinitrophenyl)phosphate (K(m) = 4.09 mM, V(max) = 2.68 x 10(-2) mM s(-1), and k(cat) = V(max)/[1] = 0.67 s(-1)). Through a potentiometric study and determination of the kinetic behavior of 1 in acetonitrile/water solution, the species present in solution could be identified, and a trinuclear monohydroxo species appears to be the most prominent catalyst under mild conditions. Complex 1 displays high efficiency in DNA hydrolytic cleavage, and complete kinetic studies were carried out (K(m) = 4.57 x 10(-4) M, K(cat)` = 3.42 h(-1), and k(cat)`/K(m) = 7.48 x 10(3) M(-1) h(-1)). Studies with a radical scavenger (dimethyl sulfoxide, DMSO) showed that it did not inhibit the activity, indicating the hydrolytic action of 1 in the cleavage of DNA, and studies on the incubation of distamycin with plasmid DNA suggest that 1 is regio-specific, interacting with the minor groove of DNA.

Vegetable Oil Derived Solvent, and Catalyst Free Click Chemistry'' Thermoplastic Polytriazoles

Azide-alkyne Huisgen click chemistry provides new synthetic routes for making thermoplastic polytriazole polymers-without solvent or catalyst. This method was used to polymerize three diester dialkyne monomers with a lipid derived 18 carbon diazide to produce a series of polymers (labelled C18C18, C18C9, and C18C4 based on monomer chain lengths) free of residual solvent and catalyst. Three diester dialkyne monomers were synthesized with ester chain lengths of 4, 9, and 18 carbons from renewable sources. Significant differences in thermal and mechanical properties were observed between C18C9 and the two other polymers. C18C9 presented a lower melting temperature, higher elongation at break, and reduced Young's modulus compared to C18C4 and C18C18. This was due to the odd-even effect induced by the number of carbon atoms in the monomers which resulted in orientation of the ester linkages of C18C9 in the same direction, thereby reducing hydrogen bonding. The thermoplastic polytriazoles presented are novel polymers derived from vegetable oil with favourable mechanical and thermal properties suitable for a large range of applications where no residual solvent or catalyst can be tolerated. Their added potential biocompatibility and biodegradability make them ideal for applications in the medical and pharmaceutical industries.

Estudos sobre a aplicação do pentacloreto de nióbio na síntese de derivados de 4-aril-3,4-di- hidrocumarinas

Coumarin is a natural active compound that can be found in many plants. The coumarins have many properties such as bronchodilator, anti-inflammatory, antioxidant, anticoagulant, antibiotics, immunomodulatory, antimicrobial and antiviral, thus, they are widely used in medical applications. More recently the coumarin derivatives have attracted the interest of many research groups in the field of new materials, for example the possibility of their use as sensitizers in dye-sensitized solar cells (DSSC) and lasers. The MCRs are defined as a process in which three or more reactants are combined in the same reaction pot, resulting in products with good structural complexity a single step, in addition to economy of atoms and selectivity and is a very important feature in modern synthetic methodology. In this work we investigated the use of niobium pentachloride as catalyst of the multicomponent reactions between phenolic derivatives, various aromatic aldehydes and β-diester derivatives in the synthesis of 4-aryl-3,4-dihydrocoumarin derivatives. The reactions were carried out at room temperature, under inert atmosphere (N2), using dichloromethane anhydrous (CH2 Cl2) as solvent, with a reaction time of most 120 hours. The products were isolated by column chromatography on silica gel and submitted to spectrometric and spectroscopic analysis. The results show that NbCl5 is an excellent agent for promoting the synthesis of 4-aryl-3,4-dihydrocoumarin derivatives through multicomponent reactions, obtaining yields varying from 45 to 95%

Design of a Dinuclear Nickel(II) Bioinspired Hydrolase to Bind Covalently to Silica Surfaces: Synthesis, Magnetism, and Reactivity Studies

Presented herein is the design of a dinuclear Ni-II synthetic hydrolase [Ni-2(HBPPAMFF)(mu-OAc)(2)(H2O)]-BPh4 (1) (H(2)BPPAMFF = 2-[(N-benzyl-N-2-pyridylmethylamine)]-4-methyl-6-[N-(2-pyridylmethyl)aminomethyl)])-4- methyl-6-formylphenol) to be covalently attached to silica surfaces, while maintaining its catalytic activity. An aldehyde-containing ligand (H(2)BPPAMFF) provides a reactive functional group that can serve as a cross-linking group to bind the complex to an organoalkoxysilane and later to the silica surfaces or directly to amino-modified surfaces. The dinuclear Ni-II complex covalently attached to the silica surfaces was fully characterized by different techniques. The catalytic turnover number (k(cat)) of the immobilized (NiNiII)-Ni-II catalyst in the hydrolysis of 2,4-bis(dinitrophenyl)phosphate is comparable to the homogeneous reaction; however, the catalyst interaction with the support enhanced the substrate to complex association constant, and consequently, the catalytic efficiency (E - k(cat)/K-M) and the supported catalyst can be reused for subsequent diester hydrolysis reactions.

The Use Of Amido- And Imido-Functionalized Alpha Hydroxy Acids In The Creation Of Biodegradable Polyesters: An Exploration Of Va

The purpose of this thesis was to synthesize biodegradable polyesters from a wide array of functionalized ¿-hydroxy acids. The initial strategy was to use amido-functionalized ¿-hydroxy acids and 2-bromopropanoyl bromide to form amido-functionalized cyclic diesters. Then, the resulting cyclic diesters would be used in ring opening polymerization to create biodegradable polyesters. However, the spontaneous rapid degradation of the secondary amido-functionalized cyclic diester structure, as seen with 2-benzamido-hydroxyacetic acid, limited ring formation to tertiary amido-functionalized ¿-hydroxy acids. Also, the hydrophilic nature of most ¿-hydroxy acids allowed water into the crystal structure of the ¿-hydroxy acid. Then, when the ¿-hydroxy acid was used in ring forming reactions, the associated water deactivated reactive reagents and limited cyclic diester synthesis. These issues led to the synthesis of hydrophobic and tertiary amido- and imido-functionalized ¿-hydroxy acids, 2-phthalimido-2-hydroxyacetic acid and 2-(1-oxoisoindolin-2-yl) hydroxyacetic acid. The new ¿-hydroxy acids were used in two new polymerization techniques, melt polycondensation and solution polymerization, instead of ring open polymerization. Melt polycondensation and solution polymerization had shown previous success in forming oligomers of amido-functionalized ¿-hydroxy acids. Melt polycondensation was conducted by heating the monomer past its melting temperature under reduced pressure. The uncatalyzed melt polycondensation of 2-(1-oxoisoindolin-2-yl) hydroxyacetic acid created polyesters (¿ 960 g/mol). The scandium(III) trifluoromethanesulfonate enhanced melt polycondensation polymerization created slightly larger oligomers (¿ 1340 g/mol). However, 2-phthalimido-2-hydroxyacetic acid was not compatible with melt polycondensation because thermal degradation occurred. Thus, solution polymerization was conducted via Steglich esterification. Only oligomeric functionalized polyesters were formed (¿ 1060 g/mol). Future work should focus on optimization of the catalyst and the reaction conditions to obtain higher molecular weight polyesters. Also, 2-(1-oxoisoindolin-2-yl) hydroxyacetic acid should be utilized in the cyclic diester synthesis technique.

Structure-Function Relations in the PI-PLC/GDPD Enzyme Superfamily

Phosphatidylinositol-specific phospholipases C (PI-PLC) are known to participate in many eukaryotic signal transduction pathways and act as virulence factors in lower organisms. Glycerophosphoryl diester phosphodiesterase (GDPD) enzymes are involved in phosphate homeostasis and phospholipid catabolism for energy production. Streptomyces antibioticus phosphatidylinositol-specific phospholipase C (SaPLC1) is a 38 kDa enzyme that displays characteristics of both enzyme superfamilies, representing an evolutionary link between these divergent enzyme classes. SaPLC1 also boasts a unique catalytic mechanism that involves a trans 1,6-cyclic inositol phosphate intermediate instead of the typical cis 1,2-cyclic inositol phosphate. The mechanism by which this occurs is still unclear. To attack this problem, we established a wide mutagenesis scan of the active site and measured activities of alanine mutants. A chemical rescue assay was developed to verify that the activity loss was due to the removal of the functional role of the mutated residue. 31P-NMR was employed in characterizing and quantifying intermediates in mutants that slowed the reaction sufficiently. We found that the H37A and H76A mutations support the hypothesis that these structurally conserved residues are also conserved in terms of their catalytic roles. H37 was found to be the general base (GB), while H76 plays the role of general acid (GA). K131 was identified as a semi-conserved key positive charge donor found at the entrance of the active site. By elucidating the SaPLC1 mechanism in relation to its active site architecture, we have increased our understanding of the structure-function relations that support catalysis in the PI-PLC/GDPD superfamily. These findings provide groundwork for in vivo studies of SaPLC1 function and its possible role in novel signaling or metabolism in Streptomyces.

TERPENE AND TERPENOID EMISSIONS AND SECONDARY ORGANIC AEROSOL PRODUCTION

Approximately 90% of fine aerosol in the Midwestern United States has a regional component with a sizable fraction attributed to secondary production of organic aerosol (SOA). The Ozark Forest is an important source of biogenic SOA precursors like isoprene (> 150 mg m-2 d-1), monoterpenes (10-40 mg m-2 d-1), and sesquiterpenes (10-40 mg m-2d-1). Anthropogenic sources include secondary sulfate and nitrate and biomass burning (51-60%), vehicle emissions (17-26%), and industrial emissions (16-18%). Vehicle emissions are an important source of volatile and vapor-phase, semivolatile aliphatic and aromatic hydrocarbons that are important anthropogenic sources of SOA precursors. The short lifetime of SOA precursors and the complex mixture of functionalized oxidation products make rapid sampling, quantitative processing methods, and comprehensive organic molecular analysis essential elements of a comprehensive strategy to advance understanding of SOA formation pathways. Uncertainties in forecasting SOA production on regional scales are large and related to uncertainties in biogenic emission inventories and measurement of SOA yields under ambient conditions. This work presents a bottom-up approach to develop a conifer emission inventory based on foliar and cortical oleoresin composition, development of a model to estimate terpene and terpenoid signatures of foliar and bole emissions from conifers, development of processing and analytic techniques for comprehensive organic molecular characterization of SOA precursors and oxidation products, implementation of the high-volume sampling technique to measure OA and vapor-phase organic matter, and results from a 5 day field experiment conducted to evaluate temporal and diurnal trends in SOA precursors and oxidation products. A total of 98, 115, and 87 terpene and terpenoid species were identified and quantified in commercially available essential oils of Pinus sylvestris, Picea mariana, and Thuja occidentalis, respectively, by comprehensive, two-dimensional gas chromatography with time-of-flight mass spectrometric detection (GC × GC-ToF-MS). Analysis of the literature showed that cortical oleoresin composition was similar to foliar composition of the oldest branches. Our proposed conceptual model for estimation of signatures of terpene and terpenoid emissions from foliar and cortical oleoresin showed that emission potentials of the foliar and bole release pathways are dissimilar and should be considered for conifer species that develop resin blisters or are infested with herbivores or pathogens. Average derivatization efficiencies for Methods 1 and 2 were 87.9 and 114%, respectively. Despite the lower average derivatization efficiency of Method 1, distinct advantages included a greater certainty of derivatization yield for the entire suite of multi- and poly-functional species and fewer processing steps for sequential derivatization. Detection limits for Method 1 using GC × GC- ToF-MS were 0.09-1.89 ng μL-1. A theoretical retention index diagram was developed for a hypothetical GC × 2GC analysis of the complex mixture of SOA precursors and derivatized oxidation products. In general, species eluted (relative to the alkyl diester reference compounds) from the primary column (DB-210) in bands according to n and from the secondary columns (BPX90, SolGel-WAX) according to functionality, essentially making the GC × 2GC retention diagram a Carbon number-functionality grid. The species clustered into 35 groups by functionality and species within each group exhibited good separation by n. Average recoveries of n-alkanes and polyaromatic hydrocarbons (PAHs) by Soxhlet extraction of XAD-2 resin with dichloromethane were 80.1 ± 16.1 and 76.1 ± 17.5%, respectively. Vehicle emissions were the common source for HSVOCs [i.e., resolved alkanes, the unresolved complex mixture (UCM), alkylbenzenes, and 2- and 3-ring PAHs]. An absence of monoterpenes at 0600-1000 and high concentrations of monoterpenoids during the same period was indicative of substantial losses of monoterpenes overnight and the early morning hours. Post-collection, comprehensive organic molecular characterization of SOA precursors and products by GC × GC-ToFMS in ambient air collected with ~2 hr resolution is a promising method for determining biogenic and anthropogenic SOA yields that can be used to evaluate SOA formation models.

Phytoplakton pigment concentrations during POLARSTERN cruise ANT-XXVIII/3 and SONNE cruise SO218

Diatoms are the major marine primary producers on the global scale and, recently, several methods have been developed to retrieve their abundance or dominance from satellite remote sensing data. In this work, we highlight the importance of the Southern Ocean (SO) in developing a global algorithm for diatom using an Abundance Based Approach (ABA). A large global in situ data set of phytoplankton pigments was compiled, particularly with more samples collected in the SO. We revised the ABA to take account of the information on the penetration depth (Zpd) and to improve the relationship between diatoms and total chlorophyll-a (TChla). The results showed that there is a distinct relationship between diatoms and TChla in the SO, and a new global model (ABAZpd) improved the estimation of diatoms abundance by 28% in the SO compared with the original ABA model. In addition, we developed a regional model for the SO which further improved the retrieval of diatoms by 17% compared with the global ABAZpd model. As a result, we found that diatom may be more abundant in the SO than previously thought. Linear trend analysis of diatom abundance using the regional model for the SO showed that there are statistically significant trends, both increasing and decreasing, in diatom abundance over the past eleven years in the region.

Distribution of benthos in late Quaternary turbidite layers of sediment cores from the North-West African continental margin

The CaCO3-contents and the fractions > 40 µm have been analysed from 5 kastenloten, one piston core and two kastengreifer taken between Senegal and Cape Verde Islands. Numerous benthonic and planktonic organisms and different terrigenous components have been distinguished. The four cores off Senegal reach middle Wuerm sediments; cores GIK12329-6 and TAG72-1 reach the V-zone and core GIK12331-4 the X-zone (Eem); the two kastengreifer contain sediments of Holocene age. Correlation of the cores has been made. Holocene sedimentation rates decrease from the shallow cores (6-11 cm/1000 years) to the deep-sea (1-2 cm/1000 years). The following climatic variations could be deduced from the sediments off the Senegal: during Holocene climate was in general as today, the Senegal river transporting fine grained material to the sea. The upper Wuerm was arid with no river influence but with red dune sand transported to the continental slope. During middle Wuerm the climate was humid again. The deep-sea cores have been influenced by eolian material from arid regions during glacial and interglacial periods, indicated by relatively high "Wuestenquarz-numbers". However, during Wuerm "Wuestenquarz-numbers" are higher than during Holocene and Eem, indicating that more intensely red coloured sediment was exposed to wind activity on the continent during this period. Varying amounts of terrigenous material and CaCO3-contents indicate varying wind strengths (lower in Holocene and Eem than during Wuerm). The boundary between humid and arid Wuerm climate was at approximately 20 °N. Influence of upwelling is difficult to establish in the sediments off Senegal, because river influence, while increasing fertility also dilutes the diatoms which are typical for upwelling. High amounts of organic carbon, low plankton/benthos ratios of foraminifers and low plankton foraminifer/radiolarian ratios in Holocene sections might be interpreted as influenced by upwelling. Turbidites occur in cores 72 and 31 and at the Holocene/Pleistocene boundary of core GIK12329-6. Their composition indicates provenance from the continental shelf of the Cape Verde Islands for core 31 and the continental shelf and slope off Senegal for core TAG72-1. Volcanic material, rare in the normal pelagic sediment of core GIK12331-4 is more frequent in the turbidites.

Eocene to Early Miocene palaeoclimate of Saxony, Germany (Table 4)

In the present study, proxy data concerning changes in atmospheric CO2 and climatic conditions from the Late Eocene to the Early Miocene were acquired by applying palaeobotanical methods. Fossil floras from 10 well-documented locations in Saxony, Germany, were investigated with respect to (1) stomatal density/index of fossil leaves from three different taxa (Eotrigonobalanus furcinervis, Laurophyllum pseudoprinceps and Laurophyllum acutimontanum), (2) the coexistence approach (CA) based on nearest living relatives (NLR) and (3) leaf margin analysis (LMA). Whereas the results of approach (1) indicate changes in atmospheric CO2 concentration, approaches (2) and (3) provide climate data. The results of the analysis of stomatal parameters indicate that the atmospheric CO2 concentration was higher during the Late Eocene than during the Early Oligocene and increased towards the Late Oligocene. A lower atmospheric pCO2 level after the Late Eocene is also suggested by an increase in marine palaeoproductivity at this time. From the Late Oligocene onwards, no changes in atmospheric CO2 concentration can be detected with the present data. For the considered sites, the results of the coexistence approach and of the leaf margin analysis document a significant cooling event from the Late Eocene to the Early Oligocene. The pCO2 decrease from the Late Eocene to the Early Oligocene indicated by the stomatal data raised in this study was thus coupled to a temperature decrease which is reflected by the present datasets. From the Early Oligocene onwards, however, no further fundamental climate change can be inferred for the considered locations. The pCO2 increase from the Early Oligocene to the Late Oligocene, which is indicated by the present data, is thus not accompanied by a climate change at the considered sites. A warming event during the Late Oligocene is, however, recorded by marine climate archives. According to the present data, no change in pCO2 occurred during the cooling event at the Oligocene/Miocene boundary, which is also indicated by marine data. The quality and validity of stomatal parameters as sensors for atmospheric CO2 concentration are discussed.

Eocene/Oligocene paleoceanography from ODP Hole 113-689B and Hole 113-690B

Middle Eocene to Late Oligocene sediments from near the crest (Site 689B, water depth 2080 m) and flank (water depth 2914 m) of the Maud Rise (62°S) have been investigated by coarse fraction analysis and have revealed the following: (1) The middle Eocene (50-40 Ma) was a period of pure carbonate sedimentation, with good preservation of carbonate microfossils. No opal > 40 µm is present. (2) In the late Eocene (40-36.5 Ma) opal fossils (mainly radiolaria, and some diatoms > 40 µm) appeared for the first time. Three maxima in opal sedimentation (Eocene/Oligocene boundary, middle early Oligocene and early/late Oligocene boundary) are separated by increases in carbonate sedimentation. The dissolution of carbonate fossils is strong in the opal-rich layers. Opal sedimentation is attributed to cooling and probably more vigorous atmospheric circulation and increased upwelling. (3) Carbonate dissolution increased with water depth in the Oligocene, whereas in the middle Eocene excellent carbonate preservation in the deeper Site 690B and stronger dissolution in the shallower Site 689B is attributed to different bottom-water characteristics. The middle Eocene bottom water probably was formed by strong evaporation at low latitudes, whereas by the earliest Oligocene formation of Antarctic Bottom Water (AABW) had set in. (4) Current influence, not on top but on the flank of the Maud Rise, could be recorded by means of larger grain sizes of benthonic and planktonic microfossils. (5) Ice-rafted debris was not found. Quartz and other minerals are very rare and not larger than 125 µm and may have been supplied by ice as well as by wind or by deep currents. Mica contents were up to 10 times higher in the middle Eocene on the flank compared to on the crest of the Maud Rise, indicating deep current supply.

(Table 1) Composition of clay minerals in DSDP Hole 75-532

An investigation of the quantitative composition of the coarse (> 40 µm) and clay (< 2 µm) fraction of HPC 532, DSDP Leg 75, in 1300 m water depth on the eastern Walvis Ridge off Southwest Africa yielded the following results: (1) The sediments reflect a complete Latest Miocene to Recent depositional history. Sedimentation rates vary between 2.3 and 7.8 cm/ka. (2) Preservation of calcium carbonate is subject to strong variations: short-term (< 100,000 years) and long-term (about 1 m.y.) cycles in carbonate dissolution have been observed, with strongest dissolution occurring during periods of lowered sea level. (3) Upwelling influence from the near-coastal upwelling centre has been detected by means of the opal content: interglacial periods show high opal contents, because the Benguela Current turned westward at about 20°S and carried opal-laden upwelled water to the west. Sediments from glacial periods, however, show opal minima. Besides these short-term cyclic variations in opal content, long-term cycles have been found, with maximum upwelling influence in the latest Pliocene/early Quaternary. (4) Each CaCO3 dissolution minimum (maximum) is correlated with an opal maximum (minimum) throughout the sediment sequence. (5) The oceanographic system off southwest Africa remained essentially unchanged since the latest Miocene: sea level rose and fell periodically on a small and on a large scale, and the Benguela Current flowed southeast-northwest and turned to the west at the latitude of Site 532 during interglacial periods, when sea level was high. (6) The climate in the near-coastal area of southwest Africa in the latitude of Site 532 has probably been arid throughout the investigated period.

Sedimentological and paleoclimatological investigation of two sediment cores off Cape Barbas, North-West Africa

Two box cores taken off Cape Barbas (North-West Africa) have been studied using three methods. The analyses of the coarse fraction, of biogenic opal and of planktonic foraminifera revealed : 1. Core GIK12310-4 penetrates Z, Y, X and upper part of W zone, whereas core GIK12379-1 penetrates Z and upper part of Y zone. 2. Holocene sedimentation rates are 2.5 cm/1000 y for core GIK12310-4 and 6.0 cm/1000 y for core GIK12379-1. During the Y zone 5 cm/l000 y were sedimented incore GIK12310-4 and > 10-20 cm/1000 y in core GIK12379-1. 3. Paleoclimatohgical results are: arid climate and relatively warm water temperatures during the Holocene (Z zone) and during X zone; humid climate and relatively cool water temperatures within the Wuerm (Y zone) (with a non-dated more arid interval found in the middle part of the Y zone) and in the upper part of the W zone. 4. Increased contents of benthos and radiolaria in the Y zone indicate upwelling. Upwelling, characterized by high content of biogenic opal and low water temperatures, was found in core GIK12310-4 at 250 to 350 cm in the lower part of the Y zone. The plankton/benthos ratio of foraminifera, the benthos/radiolaria ratio and water temperatures derived from planktonic foraminifera, differ in both cores in the Holocene, and are nearly identical during the Wuerm.