74 research outputs found
Kluyveromyces marxianus CBS 6556 growing cells as a new biocatalyst in the asymmetric reduction of substituted acetophenones
No full textThe use of microorganism growing cells is a well recognized methodology in biocatalyzed organic reactions.
A non-conventional thermotolerant Kluyveromyces marxianus yeast strain was used for the bioreduction
of different arylketones. Differently substituted ketones were converted into the corresponding
(S)-alcohols with up to 96% enantiomeric excess under very mild reaction conditions. Kluyveromyces
marxianus represents a promising biocatalyst for the production of optically active 1-arylethanols
Z-Riboside (5 amino-4-imidazolecarboxamide riboside)induces apoptosis in undifferentiated human neuroblastoma SH-SY5Y cells
No full text5’amino-4-imidazolecarboxamide riboside induces apoptosis in undifferentiated human neuroblastoma SH-SY5Y cells
No full text
Geo-archaeology, archaeometry, and history of a seismic-endangered historical site in central Apennines (Italy)
No full textAbstract Ancient human settlements accumulate essential historical, archaeological, and geological information. An example is the St. Angel Cave, which preserves a Romanesque church and a complex of lustral tubs in the Eastern Maiella Massif (Central Apennines of Italy). Historical chronicles and archaeological data show that the church dates to the 10th–11th century. The archaeometry applied to the ceramic, coin, and wooden artefacts resulting from the excavation established a chronology of the periods of use and abandonment of the St. Angel Cave. The layering of architectural elements, changes in style, and alterations of the church structure account for two collapses. The first could be related to the poorly known 1209 earthquake. In addition, we describe the damage and changes to the structure and the use of space caused probably by the 1706 and 1933 earthquakes
Elemental abundances and isotopic composition of Italian limestones: Glimpses into the evolution of the Tethys
No full textBiogenic limestones from three sections (north, central, and south) across peninsular Italy have been analysed for major and trace elements and Nd, Pb, and Sr isotopic ratios. These data are used to monitor the evolution of the Tethys Ocean from the Triassic through to the Miocene. Limestones’ major, trace, and REE elements contents are consistent with their formation in seawater with little sign of crustal, volcanic, or hydrothermal input. V/Cr and Ce/Ce* ratios indicate their deposition in oxygenated waters. Rb-Sr-Ba discrimination diagram, consistent with the immobile trace element distribution, indicates that limestone deposition took place in either marginal or open ocean environments. Ages based on stratigraphy are in good agreement with the chronostratigraphic Sr curves implying that the Tethys ocean, throughout its history, was in contact with the open, global, ocean system. Although the isotopic values of Sr and Nd are relatively restricted, Pb is extremely variable and highly radiogenic. High Pb isotope ratios characterise limestones deposited during the rifting of the southern Tethyan ocean in the Lower Jurassic and in the Lower Cretaceous, suggesting stronger crustal inputs in small basins. The weighted average, present-day, isotope values (AIL = average Italian limestone) for the Italian limestones, excluding anomalous samples, are 87Sr/86Sr = 0.70785, 143Nd/144Nd = 0.51227, and 206Pb/204Pb = 18.94, 207Pb/204Pb = 15.69, 208Pb/204Pb = 38.66. These values are useful in monitoring the fate of limestones during orogenesis and the role that they may have played in magma genesis
Enantioselective bio-reduction of prochiral ketones by the non-conventional yeast Kluyveromyces marxianus
No full textOptically active molecules are important building blocks for the synthesis of many
chemicals and biologically active compounds. Among the known catalysts, isolated
enzymes have some advantages over conventional methods in the asymmetric
synthesis, such as chemo-, regio-, and stereo-selectivity, together with very mild
reaction conditions [1].
The asymmetric synthesis accomplished by using whole-cells has also further
advantages [2, 3] because all the necessary cofactors and all required substances for
their regeneration are present in their natural environment, thus making the
catalytic system more efficient [4].
Many research groups have focused their attention on looking for non-conventional
yeasts, to study in comparison to the deeply investigated Saccharomyces cerevisiae
[5].
For several years our interests focused on using non-conventional yeasts to prepare
new EPCs: among these, thermotolerant Kluyveromyces marxianus CBS 6556, not
widely investigated in asymmetric synthesis, was preliminarly and successfully
used by us for the stereoselective bioreduction of prostereogenic keto-esters to
prepare optically active building-blocks in the synthesis of pharmacologically
active compounds [6, 7]. These studies allowed also the isolation of an unkown
ADH from this yeast [8], able to mediate the highly stereoselective bioreduction of
prostereogenic 3-oxo esters. Herein, we report the continuation of such studies, in
which the Kluyveromyces marxianus CBS 6556 is used in the bioreduction of
various prochiral ketones, with the aim to deepen its substrate specificity, turnover
rate, regio- chemo- and enantioselectivity
Igneous and sedimentary ‘limestones’: the puzzling challenge of an easy classification
No full textThis is the final version. Available on open access from the Geological Society via the DOI in this recordThe vast majority of extrusive carbonatites are calcitic rocks which may be confused with sedimentary limestones, thus requiring a disambiguation criterion. Extrusive carbonatites are classified based on quantitative criteria that tend to avoid genetic mechanisms. Carbonatite nomenclature is in progress but regulated by the IUGS norm for igneous rocks. Carbonate sedimentary rock nomenclature is mainly regulated by the Dunham (1962), Embry & Klovan (1971) and Sibley and Gregg (1987) classification systems. These limit the description of rock types from various depositional mechanisms and makes comparison with sedimentary rocks difficult. Igneous and sedimentary carbonate rocks display no apparent differences in the field and at meso-micro-scale. They may be layered, massive crystalline or show discrete clasts in a matrix which make both rock-types resemble each other. The study analyses situations in which classification inconsistencies are most common. Adopting these guidelines may increase confidence, reliability, and value in the petrographic classification of igneous and sedimentary lithologies. This study poses a challenging target. Can igneous carbonate rocks be classified using the same approach used for sedimentary carbonate rocks and vice versa? So far, the scheme chosen was arbitrary or limited to the aim of the study being undertaken. The authors start an unexperienced dialogue for the first time between volcanologists and sedimentologists by examining a range of sedimentary and volcaniclastic rock textures which may resemble each other
La Queglia carbonatitic melnöite: a notable example of an ultra-alkaline rock variant in Italy
No full textVery primitive ultramafc igneous rocks occur at Mt. La Queglia (Abruzzo, Italy). They form a strongly deformed sill–dyke
system now tilted vertically. These rocks were initially classifed as alnöite and, subsequently, have been suggested to be a
carbonatitic olivine melilitite. However, further investigation and interpretation of these rocks is needed due to the presence
of hand-specimen-scale textural variation suggesting a complex petrogenesis. We study the texture, mineral chemistry, and
whole-rock geochemistry to defne three main rock-types. (1) A brecciated rock with an ocellar texture composed of calcite
pseudomorphs after olivine and melilite, plus fresh diopside in a groundmass of mica, aegirine, garnet, calcite, apatite, perovskite, titanate and chlorite. Zoned ocelli in this rock show an amoeboid shape, agglutination, and menisci typical of a plastic
state. (2) A quenched rock showing a spinifex texture containing long feathery phenocrysts of cpx and mica suspended in a
groundmass of nepheline, aegirine, apatite, Ti–rich magnetite, plus abundant calcite and some K-feldspar and zeolites. (3)
A coarse-grained rock is composed of calcite plus intergranular glauconite, a mixture of spinel mineral group and Ti–rich
magnetite, accessory barite, pyrite, and chabazite-K. The igneous rocks at Mt. La Queglia show extreme SiO2-undersaturation
(33.5–37.3 wt% SiO2), high MgO contents and TiO2/Al2O3 ratios. Rock-type 1 has a lower Mg number Mg#=100×[Mg/
(Mg+ Fe2+)], higher Ca number Ca#=100×[Ca/(Ca+Mg)], high Cr (up to 720 ppm) Ni (up to 379 ppm), higher rare earth
elements (REE) contents as well as La/Lu ratio, compared to rock-type 2. Perovskite and chromite accumulation seems an
important agent during rock diferentiation. Rock-type 3 shows REE cross-over with rock-type 2 suggesting light (L)REE
concentration in a carbothermal residuum. Mt. La Queglia rocks are an end-member compared to other Upper Cretaceous
and Paleogene Italian lamprophyres, suggesting a low degree of melting of a HIMU (a colloquialism for “high-μ”; referring
to mantle domains with high 238U/ 204Pb) garnet-bearing mantle source
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