Inter- and intramolecular glycosylation of exo-glycals promoted by metallic Lewis acids

exo-Glycosyl carbonates were employed for inter- and intramolecular glycosylation reactions. A number of metallic Lewis Acids and solvents were examined to enhance the reactivity. The optimum conditions were found to be the use of AlCl3 in 1-nitropropane. The method was demonstrated to be useful for the intermolecular glycosyl transfer of several nucleophiles, including simple alcohols, sugars, and amino acid derivatives; however, intramolecular glycosylations were not successful.     

Ammonite fauna from uppermost Bajocian (Middle Jurassic) calcitic concretions from the Polish Jura—biogeographical and taphonomical implications

Uppermost Bajocian (Parkinsoni Zone, Bomfordi Subzone) calcitic concretions from the epicratonic basin in South-Central Poland (Polish Jura) contain numerous, well-preserved ammonites unique for this area. Characteristic of the assemblages is the presence of small, juvenile specimens. Associated with dominant parkinsoniids (Parkinsonia (Parkinsonia) aff. dorni Arkell) are lytoceratids [Nannolytoceras tripartitum (Raspail)], lissoceratids [(Lissoceras (Lissoceras) oolithicum (d'Orbigny) and Lissoceras (Microlissoceras) solitarium Zatoń and Marynowski nov. sp.)], leptosphinctids (Vermisphinctes sp.) and strigoceratids [(Strigoceras (Strigoceras) sp. juv. gr. strigifer/pseudostrigifer)], as well as fragments of phylloceratids (Phylloceras sp.). Parkinsoniids (the most numerous) are considered here as host fauna. Other ammonites, especially phylloceratids and nannolytoceratids, are supposed migrants from the Mediterranean area into the shallow epicratonic Polish Basin during the Late Bajocian sea-level rise. N. tripartitum, which has a broad geographical range probably drifted as a plankton-feeder in the upper water column and, together with phylloceratids, are considered to be unsuccessful immigrants which did not adapt to the new environment. It seems that the whole fauna, inclusive of plant remains, was accumulated by bottom currents in randomly situated depressions on the sea-floor, where carcasses became ideal nucleation sites for concretion genesis. Early diagenesis, which played an important role, resulted in well-preserved ammonite assemblages close to the original biological assemblage. Most of described ammonites (nannolytoceratids, lissoceratids, strigoceratids and leptosphinctids) are reported from the Upper Bajocian epicratonic deposits of Poland for the first time. This makes the concretions a true “taphonomic window” into latest Bajocian census biocenosis. The organic geochemistry results suggest predominance of terrestrial organic matter in both concretions and surrounding clays, with well oxygenated conditions in the sedimentary basin. The large concentrations of Δ¹³⁽¹⁷⁾diasterenes in the analysed carbonate concretions indicates that these compounds must have been formed by contact with clay minerals before formation of the carbonate concretions. The processes described may have followed early stage of diagenesis, but certainly under tens of cm to even a few meters of burial. The high negative δC¹³ values in the inner zone of the concretions suggest that concretion growth began in the sulphate reduction zone and may have continued in the methanogenesis zone.     

Extrapolation of depositional geometries of the Menorcan Miocene carbonate ramp with ground-penetrating radar

The Tortonian carbonate ramp of Menorca was previously studied on the basis of outcrops along sea-cliff outcrops. These sea cliffs, in combination with inland water wells, are the basis for a facies model for the reconstruction of the internal architecture and for characterizing the internal heterogeneities of this carbonate platform. However, any such three-dimensional reconstruction is generally limited by the given geometrical arrangement of the two-dimensional outcrops and the uncertainties of correlation with the one-dimensional wells. Here, ground-penetrating radar (GPR) has been employed in order to test and refine the depositional model. Although GPR is well known for being an excellent tool for high-resolution underground studies of sedimentary systems, the application for studying carbonate rocks is still far from routine. The reason for this discrepancy is two-fold: the minor mineralogical contrast between lithologies in carbonate rocks results in subtle reflections, and, even more important, the porosity structure in carbonates is thoroughly and repeatedly changed during diagenesis, commonly across the different facies, leading to problems in predictability of the petrophysical properties. The study of the Menorcan carbonate ramp with large distance–deep penetration GPR sections demonstrates that in spite of these difficulties, GPR is a valuable tool for extrapolating information from outcrops and wells. It is useful for characterizing heterogeneities larger than outcrop scale.     

Calcareous nannofossil productivity and carbonate production across the Middle-Late Jurassic transition in the French Subalpine Basin

The distribution pattern of calcareous nannofossils was analysed across the Middle-Late Jurassic transition in the French Subalpine Basin (south-eastern France). This basin is characterized in the hemipelagic-pelagic domain by a continuous sedimentary succession, allowing a good biostratigraphic resolution for this time interval. The nannofossil assemblages are consistently dominated by Watznaueria britannica. However, major changes in trophic and paleoenvironmental conditions are recorded across the Middle-Late Jurassic transition. An increase in marine primary productivity and cooling of surface waters is recorded across the Callovian-Oxfordian boundary, as already shown in the higher latitude setting of the eastern Paris Basin. Increased precipitation and runoff under contrasting seasonal climatic conditions (monsoon-type) has led to eutrophication of marine surface waters in the French Subalpine Basin at this period. Then, decreased runoff and associated nutrients certainly linked to drier climatic conditions lead to a decrease in calcareous nannofossil productivity during the middle part of the Early Oxfordian (mariae-cordatum ammonite Zone transition). At the Early-Middle Oxfordian transition, more favourable conditions for the nannofossil community (warmer and mesotrophic surface waters) prevailed. The pelagic (nannofossil) carbonate contribution is limited, and the carbonate fraction is predominantly of nektonic/benthic origin at the Callovian-Oxfordian transition and of allochthonous origin from carbonate platforms at the Early Oxfordian-Middle Oxfordian transition.     

Upper Cretaceous rudist biostratigraphy of the Bey Da?lar? Carbonate Platform, Western Taurides, SW Turkey

The Upper Cretaceous (Middle Cenomanian-Coniacian) successions of the Bey Da?lar? Carbonate Platform (Western Taurides, SW Turkey) are represented by rudist-bearing shallow-water limestones. Four rudist lithosomes are distinguished for the first time from the Eastern, Northern and Southern Areas of the Bey Da?lar? Autochthon. The oldest rudist assemblages dominated by caprinids are observed in the Eastern (Katran Da?) Area (caprinid lithosomes) and suggest a Middle-Late Cenomanian age. The uppermost part of the platform carbonates in the Northern Area is characterized by an association of hippuritid and radiolitid rudist bivalves dominated by Vaccinites praegiganteus (Toucas) (hippuritid lithosomes). The rudist fauna indicates the Late Turonian age, which is confirmed by the previously obtained ⁸⁷Sr/⁸⁶Sr values of well-preserved low-Mg calcite of Vaccinites praegiganteus (Toucas) shells. The rudist associations of the Southern (Susuzda?) Area are represented by two rudist formations. The lower lithosomes are mainly made up of hippuritids and radiolitids (hippuritid-radiolitid lithosomes). The stratigraphical distributions of the species of the assemblage indicate a Santonian-Early Campanian age. The rudist associations of the upper lithosomes are dominated by species of Joufia and Gorjanovicia (Joufia-Gorjanovicia lithosomes), which suggest a Late Campanian-Maastrichtian age. Identification of the rudist lithosomes yields information on the palaeobiogeographic distribution of the rudist species in the eastern Mediterranean region and also on the biostratigraphic frame of the Upper Cretaceous successions of the Bey Da?lar? Carbonate Platform.     

Enhancement of chemiluminescence for vitamin B12 analysis

In the current article, chemiluminescence (CL) from the vitamin B₁₂ and luminol reaction was studied under alkaline conditions to develop a sensitive analytical method for vitamin B₁₂ using the carbonate enhancement effect. The method was successfully applied to the determination of vitamin B₁₂ in vitamin B₁₂ tablets, multivitamin capsules, and vitamin B₁₂ injections. Experimental parameters were optimized, including luminol concentration, urea-hydrogen peroxide (urea-H₂O₂) concentration, effect of pH, and sequence of addition of reactants for obtaining maximum CL, which was not explored previously. The limit of detection was 5 pg/ml, and the linear range was 10 pg/ml to 1 μg/ml with a regression coefficient of R² = 0.9998. The importance of these experimental parameters and the carbonate enhancement effect is discussed based on the knowledge of the mechanism of oxidation of luminol and decomposition of urea-H₂O₂ in the presence of vitamin B₁₂. Extraction of vitamin B₁₂ was carried out, and the observed recovery was 97-99.2% with a relative standard deviation in the range of 0.30-1.09%. The results obtained were compared with those of the flame atomic absorption spectrometry method.     

Influences of electrolytes and glucose on formulation of carbonate apatite nanocrystals for efficient gene delivery to mammalian cells

Genetic manipulation of human cells through delivery of a functional gene or a gene-silencing element is an attractive approach to treat critical diseases very precisely and effectively. Extensive research on the genetic basis of human diseases with complete sequencing of human genome has revealed many vital genes as possible targets in gene therapy programs. On the other hand, to facilitate cell- or tissue-directed delivery of genes and gene-silencing nucleic acid sequences, both genetic and chemical engineering approaches have led to the generation of various viral and nonviral carriers. However, considering the issues of both safety and efficacy, none of the existing vectors is an ideal candidate for clinical use. We recently established pH-sensitive inorganic nanocrystals of carbonate apatite with capability of efficient intracellular delivery and release of associated DNA molecules for subsequent protein expression. Here we show a new synthetic approach for carbonate apatite crystals with stronger affinity toward DNA, leading to significant increment in both transgene delivery and expression. Moreover, CaCl₂ and NaCl, existing as the major electrolytes in the bicarbonate-buffered solution, dose-dependently govern particle size and eventually internalization and expression of particle-associated DNA.     

A micrite-dominated norian carbonate platform from Northern Calabria (Southern Italy)

Summary  This paper is focused on the facies associations of an Early-Middle Norian stratigraphic succession cropping outin the Northern Calabria (Buonvicino, Cosenza). These carbonate deposits, pertaining to the Verbicaro Unit, represent a dolomitized platform characterized by a clear dominance of automicrites over skeletal metazoans. On the basis of the chronostatigraphic data and sedimentary evolution, two stratigraphic units have been distinguished: the Lower Unit (object of the present paper) and the Upper Unit. The Lower Unit consists of an Early-Middle Norian high-relief prograding carbonate platform. The Upper Unit is represented by Middle p.p.-Upper Norian basinal deposits. Three main facies associations, indicative of different depositional settings, have been identified. The inner platform facies association is characterized by automicrite (cauliflower-columnar subordinate planar stromatolites) associated with detrital carbonates (intraclastic breccia, bioclastic grainstone and packstone). Apeculiar facies is represented by megalodontid-bearing beds. Mud-cracked horizons and low-developed teepees occur quite frequently. The margin facies association is dominated by automicrite (planar to low relief stromatolites associated with thrombolitic fenestral boundstone) and detrital carbonates with subaerial exposure features. The slope facies association includes detrital carbonates (breccia/megabreccia) associated with serpulid/sphinctozoan bioconstructions and automicrite (planar stromatolites/thrombolitic boundstone). The whole carbonate body is completely dolomitized; nevertheless the morphology and microarchitecture of carbonate components (cements, grains and automicrite) is still clearly recognizable. The dolomite Mg content ranges from 40 to 48 mole%, sometimes reaching the stoichiometric value. Cements, primary and late, represent a minor component of the rock volume; they occur more frequently on the margin and upper slope setting. Quantitative tacies analyses lead to the following conclusions:

Sedimentation on three caribbean atolls: Glovers reef,lighthouse reef and turneffe Islands,belize

Summary The chief mode of carbonate sedimentation on the Belizean atolls Glovers Reef, Lighthouse Reef and Turneffe Islands is the accumulation of organically-derived particles. Variations in the distribution of the composition and grain-sizes of surface sediments, collected along transects across the atolls, are environmentally controlled. Two major sediment types may be distinguished. (1) Reef and fore reef sediments are dominated by fragments of coral, coralline algae andHalimeda. Mean grain-sizes range from 1–2 mm. (2) Back reef sediments contain more mollusk fragments, more fine-grained sediment (<125 μm) and appear to have fewerHalimeda fragments. In addition, sediments from inner platforms and shallow lagoonal parts of Glovers and Lighthouse Reefs comprise non-skeletal grains, namely fecal pellets. Sediments from lagoonal patch reefs may contain up to 20% coral fragments. Mean grain-sizes range from 0.1–1 mm and are finest on the inner platform and lagoon floor of the back reef environment. Within the reef and fore reef environments, it is not possible to distinguish sub-environments on the basis of textural and compositional differences of the sediments. Sediments from patch reefs contrast with those from back reef lagoons and inner platforms and are similar in terms of grain-sizes and compositions to reef and fore reef surface sediments. Non-skeletal grains forming in shallow parts of the back reef in Glovers and Lighthouse Reefs are interpreted to be indurated by interstitial precipitation of calcium carbonate from warm, supersaturated water flushing the sediment. The lack of hardened non-skeletal particles in the back reef sediments of Turneffe Islands is most probably due to the abundance of muddy, organic-rich sediment in the well-protected lagoon. Fine sediment is less permeable and organic films prevent cement overgrowth on particles.     

Photosynthesis and photorespiration in a mutant of the cyanobacterium Synechocystis PCC 6803 lacking carboxysomes

A mutant of the cyanobacterium Synechocystis PCC 6803 was obtained by replacing the gene of the carboxylation enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) with that of the photosynthetic bacterium Rhodospirillum rubrum. This mutant consequently lacks carboxysomes — the protein complexes in which the original enzyme is packed. It is incapable of growing at atmospheric CO₂ levels and has an apparent photosynthetic affinity for inorganic carbon (C_i) which is 1000 times lower than that of the wild type, yet it accumulates more C_i than the wild type. The mutant appears to be defective in its ability to utilize the intracellular C_i pool for photosynthesis. Unlike the carboxysomal carboxylase activity of Rubisco, which is almost insensitive to inhibition by O₂ in vitro, the soluble enzyme is competitively inhibited by O₂. The photosynthetic rate and C_i compensation point of the wild type were hardly affected by low O₂ levels. Above 100 μM O₂, however, both parameters became inhibited. The CO₂ compensation point of the mutant was linearly dependent on O₂ concentration. The higher sensitivity of the mutant to O₂ inhibition than that expected from in-vitro kinetics parameters of Rubisco, indicates a low capacity to recycle photorespiratory metabolites to Calvin-cycle intermediates.