Biodiversity of living benthic foraminifera: How many species are there?

In ecological studies involving the analysis of  2.4 million living (stained) individual tests, to date  2140 species of benthic foraminifera have been recorded. Of these 602 species are agglutinated, 341 porcelaneous and 1197 hyaline. The numbers of species in the major environments are: marginal marine 701 (in  1.5 million individuals), shelf 989 (in  0.6 million individuals) and deep sea 831 (in  0.3 million individuals). 381 species occur in more than one major environment. Overall  33% have abundance of > 10% while  67% are of minor abundance (< 10%). The majority of species are rare, most are endemic and very few are cosmopolitan (5% or less). To estimate the potential total number of living species the following factors need to be quantified: the proportion of species already named (here considered unlikely to be less than 50% of the potential total), the number of species currently known to be dead but for which living representatives may yet to be found (assumed to be 5% = 107 species), and the proportion of species that are synonyms (10–25% = 214 to 535 species). Assuming that 50% of species have already been named (2140 + 107 = 2247), the potential total ranges from  3959 to  4280 species for 10% synonymy to  3210 to  3531 species for 25% synonymy.     

Extraction and characterization of hemicelluloses from flax shives by different methods

Hemicelluloses were extracted from flax shives using pressurized low-polarity water (PLPW), pressurized aqueous ethanol (PAE), microwave-assisted water (MW-Water) or aqueous ethanol (MW-EtOH), and precipitated with ethanol. Hemicelluloses still remaining in solution were further separated using ultrafiltration. All samples were characterized with chemical analysis, ion-moderated partition chromatography (IMP), size exclusion chromatography (SEC), and Fourier transform infrared (FT-IR) spectroscopy. PLPW, PAE, MW-Water and MW-EtOH extracted 90, 80, 18, and 40% of the total hemicelluloses, respectively. The molecular weight of the ethanol-precipitated hemicelluloses ranged from approximately 11,000 to 40,000 Da and the ethanol-soluble low-molecular weight hemicelluloses were about 1700 Da. High-molecular weight hemicellulose isolated from PAE extracts contained 23% lignin, while that from the PLPW extracts contained 5% lignin. Low-molecular weight hemicelluloses separated by ultrafiltration from PLPW and PAE extracts contained similar amounts of lignin (20%). However, the yield of low-molecular weight hemicelluloses from PLPW was higher (15%) compared to that from PAE (6%). The FT-IR results revealed the specific band maximum at 1220 cm⁻¹ and the bands between 1175 and 1000 cm⁻¹ which are typical of xylans.     

The control of transmembrane helix transverse position in membranes by hydrophilic residues

The ability of hydrophilic residues to shift the transverse position of transmembrane (TM) helices within bilayers was studied in model membrane vesicles. Transverse shifts were detected by fluorescence measurements of the membrane depth of a Trp residue at the center of a hydrophobic sequence. They were also estimated from the effective length of the TM-spanning sequence, derived from the stability of the TM configuration under conditions of negative hydrophobic mismatch. Hydrophilic residues (at the fifth position in a 21-residue hydrophobic sequence composed of alternating Leu and Ala residues and flanked on both ends by two Lys) induced transverse shifts that moved the hydrophilic residue closer to the membrane surface. At pH 7, the dependence of the extent of shift upon the identity of the hydrophilic residue increased in the order: L < GYT < RH < S < P < K < EQ < N < D. By varying pH, shifts with ionizable residues fully charged or uncharged were measured, and the extent of shift increased in the order: L < GYH^oT < E^oR < S < P < K⁺< QD^oH⁺ < NE^– < D^–. The dependence of transverse shifts upon hydrophilic residue identity was consistent with the hypothesis that shift magnitude is largely controlled by the combination of side chain hydrophilicity, ionization state, and ability to position polar groups near the bilayer surface (snorkeling). Additional experiments showed that shift was also modulated by the position of the hydrophilic residue in the sequence and the hydrophobicity of the sequence moved out of the bilayer core upon shifting. Combined, these studies show that the insertion boundaries of TM helices are very sensitive to sequence, and can be altered even by weakly hydrophilic residues. Thus, many TM helices may have the capacity to exist in more than one transverse position. Knowledge of the magnitudes of transverse shifts induced by different hydrophilic residues should be useful for design of mutagenesis studies measuring the effect of transverse TM helix position upon function.     

Fine structure characterization of amylopectins from grain amaranth starch

The aim of this study was to determine the fine structure of amylopectin from grain amaranth. Amaranthus amylopectin was hydrolyzed with α-amylase, and single clusters and a group of clusters (domain) were isolated by methanol precipitation. The domain and the clusters were treated with phosphorylase a and then β-amylase to remove all external chains, whereby the internal structure was obtained. The ,β-limit dextrins were analyzed on Sepharose CL 6B. The average DP (degree of polymerization) and peak-DP values of fractions of clusters were 57 and 82, respectively; the values of the domain were 137 and 309, respectively. The unit chain length profiles were analyzed by high-performance anion-exchange chromatography with pulsed amperometric detector (HPAEC–PAD). The results showed that the domain fraction contained 2.2 clusters, and single clusters were composed of 13 chains. The ,β-limit dextrins of the clusters were further hydrolyzed with α-amylase to characterize their building block composition. The average DP of the branched blocks was 11 and they contained on average 2.5 chains. Their average chain length, internal chain length, and degree of branching were approximately 4.3, 2.8, and 14, respectively. A cluster consisted of 6 branched blocks, and the internal chain length between the blocks was 6.8.     

Propionic acid production from glycerol by metabolically engineered Propionibacterium acidipropionici

Large amounts of crude glycerol produced in the biodiesel industry can be used as a low-cost renewable feedstock to produce chemicals and fuels. Compared to sugars (sucrose, glucose, xylose, etc.), glycerol has a lower reducing level, which is of benefit to the production of reduced chemicals. In this work, glycerol as the sole carbon source in propionic acid fermentation by metabolically engineered Propionibacterium acidipropionici (ACK-Tet) was studied. It was found that the adapted ACK-Tet mutant could use glycerol for its growth and produced propionic acid at a high yield of 0.54–0.71 g/g, which was much higher than that from glucose (0.35 g/g). In addition, the production of acetic acid in glycerol fermentation was much less than that from glucose. Thus, glycerol fermentation produced a high purity propionic acid with a high propionic acid to acetic acid ratio of 22.4 (vs. 5 for glucose fermentation), facilitating the recovery and purification of propionic acid from the fermentation broth. The highest propionic acid concentration obtained from glycerol fermentation was 106 g/L, which was 2.5 times of the highest concentration (42 g/L) previously reported in the literature.     

Optimization of glutaryl-7-aminocephalosporanic acid acylase expression in E. coli

A recombinant glutaryl-7-aminocephalosporanic acid acylase (GLA) from Pseudomonas N176 has been over-expressed in BL21(DE3)pLysS Escherichia coli cells. By alternating screenings of medium components and simplified factorial experimental designs, an improved microbial process was set up at shake-flask level (and then scaled up to 2L-fermentors) giving a 80- and 120-fold increase in specific and volumetric enzyme productivity, respectively. Under the best expression conditions, 1380 U/g cell and 16,100 U/L of GLA were produced versus the 18 U/g cell and the 140 U/L obtained in the initial standard conditions. Osmotic stress caused by the addition of NaCl, low cell growth rate linked to high biomass yield in the properly-designed rich medium, optimization of the time and the amount of inducer’s addition and decrease of temperature during recombinant protein production, represent the factors concurring to achieve the reported expression level. Notably, this expression level is significantly higher than any previously described production of GLAs. High volumetric production, cost reduction and the simple one-step chromatographic purification of the His-tagged recombinant enzyme, makes this GLA an economic tool to be used in the 7-ACA industrial production.     

Trends in aluminium export from a mountainous area to surface waters, from deglaciation to the recent: Effects of vegetation and soil development, atmospheric acidification, and nitrogen-saturation

We reconstructed the history of terrestrial export of aluminium (Al) to Plešné Lake (Czech Republic) since the lake origin 12,600 year BC, and predicted Al export for 2010–2050 on the basis of previously published and new data on mass budget studies, palaeolimnological data, and MAGIC modelling. We focused on three major Al forms; ionic Al (Al_i), organically-bound Al (Al_o), and particulate Al hydroxide [Al(OH)₃]. In early post-glacial time, Plešné Lake received high terrestrial export of Al, but with a minor proportion of Al(OH)₃ (4–25 μM), and concentrations of Al_i and Al_o were negligible. Since the forest and soil development (9900–9000 year BC), erosion has declined and soil organic acids increased export of Al_o from soils. The terrestrial Al_o leaching (7.5 μM) persisted throughout the Holocene until the industrial period. Then, Al_i concentrations continuously increased (up to 28 μM in the mid-1980s) due to atmospheric acidification; the Al_i leaching was mostly associated with sulphate. The proportion of Al_i associated with nitrate has been increasing since the beginning of lake recovery from acidification after 1990 due to reduction in sulphur deposition and nitrogen-saturation of the catchment, leading to persistent nitrate leaching. Currently, nitrate has become the dominant strong acid anion and the major Al_i carrier. Al_o (5.5 μM) is predicted to dominate Al concentrations around 2050, but the predicted Al_i concentrations (4 μM) are uncertain because of uncertainty associated with the future nitrate leaching and its effect on soils.     

The Pandinus imperator haemolymph lipoprotein, an unusual phosphatidylserine carrying lipoprotein

The haemolymph lipoprotein of the scorpion, Pandinus imperator was isolated and characterised. Contrary to the lipoproteins of insects and the discoidal HDL-lipoproteins of a crayfish and polychaete, the Pandinus lipoprotein consists of three instead of two apoproteins (apoPiLp I = 230 kDa, apoPiLp II = 130 kDa and apoPiLp III = 120 kDa). The apolipoproteins are arranged in varying stoichiometries as judged by cross-linking experiments. In lipoprotein samples from individual animals, the two smaller subunits occurred in a 1:1 stoichiometry, while the relative amount of the 230 kDa peptide varied. The lipoprotein is a slightly heart-shaped HDL with a diameter of 15 nm. It is present in two densities of 1100 and 1190 kg/m³, of which the latter is by far more abundant. The native molecular mass was estimated to be 500 kDa. The lipid content was determined as 33.5% and consists of 70% neutral lipids and 30% phospholipids. Strikingly, 42.5% of the phospholipids is phosphatidylserine while phosphatidylcholine and phosphatidylethanolamine account for 55.1% and 2.3%, respectively. Carbohydrate analysis suggests the presence of only high-mannose-type N-glycans. N-glycan profiling shows glycans corresponding to a size of 8.0–11.5 hexose units.     

Decomposition of four macrophytes in wetland sediments: Organic matter and nutrient decay and associated benthic processes

Decomposition rates of Phragmites australis, Carex riparia, Nuphar luteum and Salvinia natans and benthic processes were measured from December 2003 to December 2004 in a shallow wetland (Paludi di Ostiglia, Northern Italy) by means of litter bags and intact cores incubations. Decay rate was highest for N. luteum (k = 0.0152 d⁻¹), intermediate for S. natans (k = 0.0041 d⁻¹) and similar for P. australis (k = 0.0027 d⁻¹) and C. riparia (k = 0.0028 d⁻¹).Benthic metabolism followed a seasonal pattern with summer peaks of O₂ demand and TCO₂, CH₄ and NH₄⁺ efflux whilst soluble reactive phosphorus (SRP) fluxes were negligible also under hypoxic conditions, indicating that P was mainly retained by sediment. The initial C:P ratio was similar in N. luteum and S. natans (170) and significantly lower than that of P. australis and C. riparia (360). During the detritus decay P was progressively lost by N. luteum and S. natans tissues, whereas, after an initial leaching, it was probably re-used during the microbial decomposition of the more refractory P. australis and C. riparia detritus. Nuphar luteum, P. australis and S. natans had comparable initial C:N mass ratio (15), significantly lower than that of C. riparia (26). The C:N ratio was rather constant for N. luteum (12.9 ± 1.5) and S. natans (14.6 ± 0.9), decreased slightly to below 20 for C. riparia and increased up to 30 for P. australis. Overall, differences among species were likely due to the recalcitrance of decomposing detritus, whilst process rates were controlled by limitation of microbial processes by nutrients and electron acceptor availability.     

Synthesis of novel ketoconazole derivatives as inhibitors of the human Pregnane X Receptor (PXR; NR1I2; also termed SXR, PAR)

PXR, pregnane X receptor, in its activated state, is a validated target for controlling certain drug–drug interactions in humans. In this context, there is a paucity of inhibitors directed toward activated PXR. Using prior observations with ketoconazole as a PXR inhibitor, the target compound 3 was synthesized from (s)-glycidol with overall 56% yield. (+)-Glycidol was reacted with 4-bromophenol and potassium carbonate in DMF to yield the ring opened compound 6. This was then heated to reflux in benzene along with 2′, 4′-difluoroacetophenone and catalytic amount of para-toluene sulfonic acid to yield 8. The resultant acetal 8 was then functionalized using Palladium chemistry to yield the target compound 3. The activity of the compound was compared with ketoconazole and UCL2158H. However, in contrast with ketoconazole (IC₅₀  0.020 μM; 100% inhibition), 3 has negligible effects on inhibition of microsomal CYP450 (maximum 20% inhibition) at concentrations >40 μM. In vitro, micromolar concentration of ketoconazole is toxic to passaged human cell lines, while 3 does not exhibit cytotoxicity up to concentrations 100 μM (viability >85%). This is the first demonstration of a chemical analog of a PXR inhibitor that retains activity against activated PXR. Furthermore, in contrast with ketoconazole, 3 is less toxic in human cell lines and has negligible CYP450 activity.     

Late Neogene planktonic foraminifera of the Cibao Valley (northern Dominican Republic): Biostratigraphy and paleoceanography

An assemblage of planktonic foraminifera is described from 125 samples taken from the Cercado, Gurabo, and Mao Formations in the Cibao Valley, northern Dominican Republic. The primary objectives of this study are to establish a biochronologic model for the late Neogene of the Dominican Republic and to examine sea surface conditions within the Cibao Basin during this interval. The Cercado Formation is loosely confined to Zones N17 and N18 ( 7.0–5.9 Ma). The Gurabo Formation spans Zones N18 and N19 ( 5.9–4.5 Ma). The Mao Formation is placed in Zone N19 ( 4.5–3.6 Ma). Changes in the relative abundances of indicator species are used to reconstruct sea surface conditions within the basin. Increasing relative abundances of Globigerinoides sacculifer and Globigerinoides ruber, in conjunction with a decreasing relative abundance of Globigerina bulloides, suggests the onset of increasing sea surface temperature and salinity in conjunction with diminishing primary productivity at 6.0 Ma. Abrupt increases in the relative abundances of G. sacculifer and G. ruber at 4.8 Ma suggest a major increase in sea surface temperature and salinity in the early Pliocene. The most likely mechanism for these changes is isolation of the Caribbean Ocean through progressive restriction of Pacific–Caribbean transfer via the Central American Seaway. Periods of high productivity associated with upwelling events are recorded in the upper Cercado Formation ( 6.1 Ma) and in the middle Mao Formation ( 4.2 Ma) by spikes in G. bulloides and Neogloboquadrina spp. respectively. The timing of major increases in sea surface salinity and temperature as well as decreasing productivity ( 4.8 Ma) and periods of upwelling ( 6.1and 4.2 Ma) in the Cibao Basin generally corroborate previously suggested Caribbean oceanographic changes related to the uplift of Panama. Changes in sea surface conditions depicted by paleobiogeographic distributions in the Cibao Basin suggest that shoaling along the Isthmus of Panama had implications in a shallow Caribbean basin as early as 6.0 Ma. Major paleobiologic changes between 4.8 and 4.2 Ma likely represent the period of final closure of the CAS and a nearly complete disconnection between Pacific and Caribbean water masses. This study illustrates the use of planktonic foraminifera in establishing some paleoceanographic conditions (salinity, temperature, productivity, and upwelling) within a shallow water basin, outlining the connection between regional and localized oceanographic changes.     

Purification and characterization of a novel ribosome-inactivating protein from seeds of Trichosanthes kirilowii Maxim

A novel ribosome-inactivating protein, designated Trichosanthrip, was purified from mature seeds of Trichosanthes kirilowii Maxim by cation-exchange and gel-filtration chromatography. Trichosanthrip migrated as a single band in SDS–PAGE, with an apparent molecular mass of 13 kDa. The molecular mass of Trichosanthrip was 10,964.617 Da as determined by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Trichosanthrip showed N-glycosidase activity on 28 S rRNA and strongly inhibited cell-free protein synthesis, with an IC₅₀ of 1.6 ng/ml. Liquid chromatography–tandem mass spectrometry showed that Trichosanthrip was a novel protein with similar sequence to other proteins present in members of the Cucurbitaceae.     

Pronase digestion of brush border membrane-bound Cry1Aa shows that almost the whole activated Cry1Aa molecule penetrates into the membrane

Bacillus thuringiensis insecticidal proteins, Cry toxins, following ingestion by insect larvae, induce insecticidal effect by penetrating the brush border membranes (BBM) of midgut epithelial cells. Purified, activated B. thuringiensis Cry1Aa bound to Bombyx mori BBMV or unbound Cry1Aa were vigorously digested with Pronase. Both digests were compared by Western blotting. Free Cry1Aa was digested to α-helix and/or to amino acids at 1 mg Pronase/mL within 2.4 h at 37 °C. Whereas, BBMV-bound Cry1Aa was very resistant to Pronase digestion and even at 2 mg for 24 h, 7.5 kDa and 30 kDa peptide were detected by α-2,3 antiserum, and α-4,5 and α-6,7 antisera, respectively. Another 30 kDa peptide was also detected by β-6-11 and domain III antisera. These fragments are believed either to be embedded in or to strongly interact with the BBMV. The 7.5 and former 30 kDa peptides are thought to be derived from α-2,3 helix and stretch of α-4 to α-7 helices. Furthermore the latter 30 kDa was thought to include the stretch of β-6 to domain III. Moreover, the embedded Cry1Aa molecule appears to be segregated in some areas of β-1-5 sheets, resulting in the above two 30 kDa peptides. From these digestion patterns, we proposed new membrane insertion model for single Cry1Aa molecule. On the other hand, in digestion of BBMV-bound Cry1Aa, 15 kDa peptide which was recognized only by α-4,5 antiserum was observed. This fragment must be dimeric α-4,5 helices and we discussed the origin of this peptide.     

CCK-8S activates c-Fos in a dose-dependent manner in nesfatin-1 immunoreactive neurons in the paraventricular nucleus of the hypothalamus and in the nucleus of the solitary tract of the brainstem

Recently, a new neuropeptide, named nesfatin-1, was discovered. It has been reported that nesfatin-1 inhibits food intake after injection into the third ventricle as well as intraperitoneal (ip) injection. Cholecystokinin (CCK) is well established to play a role in the regulation of food intake. The aim of the study was to examine whether CCK-8S injected ip modulates neuronal activity in nesfatin-1 immunoreactive (ir) neurons localized in the PVN and in the nucleus of the solitary tract (NTS). Additionally, tyrosine hydroxylase-immunoreactivity (TH-ir) in the PVN was determined to assess the distribution of TH-ir fibers in relation to nesfatin-1-ir. Non-fasted male Sprague-Dawley rats received 6 or 10 µg CCK-8S/kg or vehicle solution (0.15 M NaCl; n = 4 all groups) ip. The number of c-Fos-ir neurons was determined in the PVN, arcuate nucleus (ARC), and NTS. Double staining procedure for nesfatin-1 and c-Fos revealed that CCK-8S increased significantly and in a dose-dependent manner the number of c-Fos positive nesfatin-1-ir neurons in the PVN ( 4-fold and 7-fold) and NTS ( 9-fold and 26-fold). Triple staining in the PVN showed a dose-dependent neuronal activation of nesfatin-1 neurons that were colocalized with CRF and oxytocin. Double labeling against nesfatin-1 and TH revealed that nefatin-1-ir neurons were encircled in a network of TH-ir fibers in the PVN. No effect on the number of c-Fos-ir neurons was observed in the ARC. These results suggest that the effects of CCK on the HPA axis and on food intake may, at least in part, be mediated by nesfatin-1-ir neurons in the PVN.     

Historical biogeography, phylogenetic relationships and intraspecific diversity of agamid lizards in the Central Asian deserts of Kazakhstan and Uzbekistan

The Central Asian agamid lizards are ecologically and morphologically diverse, occurring across a broad range of desert environments in this biogeographically important region. It is probable that past climatic shifts have significantly influenced the diversification patterns and distributions of the agamid lizards of this region. To assess this within a phylogenetic framework we sequenced a 1200 bp region of mitochondrial DNA and a 1200 bp nuclear gene (RAG-1), incorporating both inter- and intraspecific sampling across Central Asian agamids. Our topology and divergence time estimates support an Eocene origin of the Agaminae subfamily on the Indian subcontinent, coinciding with the collision of India into Eurasia. The onset of aridification in Central Asia during the Late Oligocene, resulting from the retreat of the Paratethys Sea and the intensified uplift of the Tibetan–Himalayan complex, probably played an important role in the diversification of Phrynocephalus, one of the three genera studied. Intensification of aridity and geologic events in the Plio-Pleistocene and Quaternary glacial cycling probably had a significant influence on intraspecific diversification patterns within Phrynocephalus.     

Phylogeography of the frog Leptodactylus validus (Amphibia: Anura): Patterns and timing of colonization events in the Lesser Antilles

The frog Leptodactylus validus occurs in northern South America, Trinidad and Tobago, and the southern Lesser Antilles (Grenada and St. Vincent). Mitochondrial DNA sequences were used to perform a nested clade phylogeographic analysis (NCPA), to date colonization events, and to analyze colonization patterns using on a relaxed molecular clock and coalescent simulations. L. validus originated on the mainland and first colonized Trinidad with subsequent independent colonizations of Tobago and the Lesser Antilles from Trinidad. The NCPA suggests a historical vicariant event between populations in Trinidad and Tobago from those in the Lesser Antilles. The colonization of Trinidad occurred 1 million years ago (mya) and the colonization of the Lesser Antillean islands occurred 0.4 mya. The coalescent approach supported the scenario where L. validus dispersed from Trinidad to St. Vincent and from there to Grenada, a dispersal event that could have been mediated by human introduction as recent as 1600 years ago.     

Demographic and phylogeographic histories of two venomous North American snakes of the genus Agkistrodon

Many studies have revealed that lineages currently inhabiting formerly glaciated areas were pushed into southern glacial refugia and have expanded into their modern range since the last glacial maximum. There have been few studies that compare the effects of glacial cycles on lineage diversification and historical demography in closely related species with overlapping ranges. In this study we compare phylogeographic structure, historical demography, and approximate lineage age in two closely related and broadly co-occurring venomous snakes in eastern North America, the cottonmouth (Agkistrodon piscivorus) and copperhead (A. contortrix) using sequences from the mtDNA gene cytochrome b. We inferred three geographic lineages of A. contortrix and two of A. piscivorus with no common geographic or temporal pattern of lineage diversification identified for these species. Lineage diversification occurred in the Late Pliocene for A. piscivorus (2.5 mya) and in the Early Pleistocene for A. contortrix (1.5 mya). Demographic estimates revealed population expansion following the last glacial maximum (20,000 years ago) in two lineages of A. contortrix (the Central clade and Eastern clade) and one lineage of A. piscivorus (the Continental clade). The Florida clade of A. piscivorus is the only lineage for which constant population size through time was inferred, possibly due to stable populations persisting in areas unaffected by glacial advances. Our data suggest that unique habitat preferences may have shaped both the phylogeographic and demographic histories of each species.     

Design, synthesis of novel peptidomimetic derivatives of 4-HPR for rhabdoid tumors

Rhabdoid tumors (RTs) are an extremely aggressive pediatric malignancy that results from loss of the INI1/hSNF5 tumor suppressor gene. Loss of INI1 results in aberrant expression of Cyclin D1, which supports rhabdoid tumorigenesis and survival. 4-HPR, a synthetic retinoid that down-modulates Cyclin D1, has shown promise in treating various tumors including RTs. In this study, we have generated a chemical library of peptidomimetic derivatives of 4-HPR in an attempt to create a more biologically active compound for use as a therapeutic agent against RTs and other tumors. We have synthesized novel peptidomimetic compound by substituting alkene backbone with a ring structure that retains the biological activity in cell culture models of rhabdoid tumors. We further identified derivative of peptidomimetic compound (11d, IC₅₀  3 μM) with approximately five times higher potency than 4-HPR (1, IC₅₀  15 μM) based on a survival assay against rhabdoid tumor cells. These studies indicate that peptidomimetic derivatives that retain the cytotoxic activity are promising novel chemotherapeutic agents against RTs and other tumors.     

Variations on the SnCl4 and CF3CO2Ag-promoted glycosidation of sugar acetates: a direct, versatile and apparently simple method with either α or β stereocontrol

Glycosidation of sugar peracetates (d-gluco, d-galacto) with SnCl₄ and CF₃CO₂Ag led to either 1,2-cis-, or 1,2-trans-glycosides, depending primarily on the alcohols used. In particular, 1,2-trans-glycosides, expected from acyl-protected glycosyl donors, were formed in high yields with alcohols sharing specific features such as bulkiness, presence of electron-withdrawing groups or polyethoxy motifs. In contrast, simple alcohols afforded 1:1 mixtures of 2,3,4,6-tetra-O-acetyl, and 3,4,6-tri-O-acetyl 1,2-cis-glycosides due to anomerization and/or acid-catalyzed fragmentation of 1,2-orthoester intermediates. After reacetylation or deacetylation, acetylated or fully deprotected 1,2-cis-glycosides (α-d-gluco, α-d-galacto) were obtained in 90% yields by a simple and direct method.     

Early Neogene biochemostratigraphy of Pohang Basin: a paleoceanographic response to the early opening of the Sea of Japan (East Sea)

The location of the Pohang Basin near the Korea Strait in the southwest of the Sea of Japan (East Sea) makes this area appropriate for providing a record of paleoenvironmental/biotic changes associated with the early Neogene (16.5 Ma) opening of this gateway to the Pacific Ocean. Stable isotopic and planktonic foraminiferal records are presented that assist with the understanding of paleoenvironmental changes in the Sea of Japan resulting from the opening of the Korea Strait. The oldest sediments of early Neogene age of the Pohang Basin overlie Cretaceous basement and are Early Miocene (>16.5 Ma) shallow, estuarine facies containing a benthic foraminiferal assemblage dominated by Ammonia beccarii (L.). The oldest early Neogene planktonic foraminiferal assemblages in the basin are 16.5 Ma in age (latest Early Miocene foraminiferal zone N8). The migration of these planktonic assemblages to the Sea of Japan at that time appears to have resulted from the initial opening of the Korea Strait. The overlying early Neogene marine sequence of the Pohang Basin extends from 16.5 Ma (Zone N8) through 14 Ma (Zone N10). Change in the oxygen isotopic record of the Pohang Basin sequence suggests strong local paleoenvironmental control related to the early opening of the Korea Strait. Early Middle Miocene isotopic temperatures of planktonic foraminifera are relatively cool at 15 Ma at a time when global temperatures were high in the middle/low latitude regions. It was not until 14.8 Ma that isotopic temperatures of planktonic foraminifera increased markedly. This distinct warming is inferred to reflect the major intrusion of the Kuroshio Current into the Sea of Japan probably as a result of further critical opening and deepening of the Korea Strait. At this time planktonic foraminifera increased in abundance reflecting expanding oceanic influence. A cooling that followed at 14.5 Ma, when the strait was well open is unlikely to reflect local tectonic control on the paleoceanography, but global cooling during the early Middle Miocene associated with the expansion of the East Antarctic ice sheet.