3,621 research outputs found
Solid-Phase Lipase-CuNPs Biohybrids as Catalysts for One-Pot Parallel Synthesis of 2,3,4-Triacetyl-D-Gluconic Acid
Solid-phase lipase/metal nanobiohybrids, generated by growth of copper nanoparticles on enzyme matrixes immobilized on graphene, were used as heterogeneous catalysts with dual-activity for the regioselective production of 2,3,4-triacetyl-D-gluconic acid from α-peracetylated-glucose in a one-pot parallel process combining a lipase-mediated regioselective hydrolytic monodeprotection with a metal-catalyzed oxidation in aqueous media. A novel synthetic strategy, based on the in situ fabrication of Cu nanoparticles induced by lipase molecules specifically immobilized on a multi-layer graphene material by interfacial adsorption fixing them in the active open conformation, has been described. Thermomyces lanuginosus lipase was firstly used to prepare the functionalized multi-layer graphene from graphite as a biographene preparation (Biographene, BIOG), support used to successfully immobilize Candida rugosa lipase (CRL). This immobilized form BIOG-CRL was further used to create successful active bifunctional enzyme-metal nanoarchitectures. Two different Cu-lipase hybrids were synthesised, where Cu species and nanoparticles size were different depending on the methodology. Regioselectivity and stability of the hybrids were evaluated successfully in the production of monosaccharide building blocks, besides the robustness of the hybrids in recyclability experiments. These findings highlight the potential of these solid-phase nanoarchitectures as useful tools in the synthesis of complex glycoderivatives for use in food, medicine, and cosmetics
On-board quality preservation of megrim (Lepidorhombus whiffiagonis) by a novel ozonised-slurry ice system
6 páginas, 3 tablas.-- The final publication is
available at www.springerlink.comThe use of a combined ozonised-slurry ice system
was investigated as a new refrigeration system for the
on-board storage of megrim (Lepidorhombus whiffiagonis),
a fish species that is usually stored aboard fishing vessels
for 1 to 2 weeks. The time elapsed between the catch and
unloading at the harbour affects its quality and commercial
value directly. Microbiological, chemical and sensory
analyses were carried out in megrim after 2 weeks of onboard
storage in ozonised slurry ice, slurry ice or flake
ice, and for an additional period of 6 days. Sensory analyses
revealed that megrim specimens stored in ozonised
slurry ice (oSI600 batch) maintained A quality even after
20 days of storage, while counterpart batches stored in
flake ice showed B quality at unloading, after 14 days of
on-board storage. Storage in ozonised slurry ice (oSI600
batch) also led to significantly (p<0.05) lower counts of
aerobic mesophiles, psychrotrophic bacteria, Enterobacteriaceae
and proteolytic microorganisms in megrim muscle
as compared with flake ice. Biochemical analyses revealed
that the use of ozonised-slurry ice or slurry ice alone slowed
down the formation of total volatile base-nitrogen (TVBN)
and trimethylamine-nitrogen (TMA-N) in comparison
with storage in flake ice, also allowing a better control of
pH. Lipid hydrolysis and oxidation events also occurred at
a lower rate in the ozonised-slurry ice and slurry ice batches
than in the flake ice batch. The present study demonstrates
that the combination of slurry ice and ozone for the on-board storage of megrim is advisable, thus improving the
quality and extending the shelf life of this fish species.This work was supported
through a project grant by the Secretar´ıa Xeral de I+D from the
Xunta de Galicia (Project PGIDIT04TAL015E).Peer reviewe
Soil Carbon in Agroforestry Systems: An Unexplored Treasure?
Soil organic matter (SOM), which contains more reactive organic carbon (C) than any other single terrestrial pool, plays a major role in determining C storage in ecosystems and regulating atmospheric concentrations of carbon dioxide (CO2)^1^. Agroforestry, the practice of growing trees and crops in interacting combinations on the same unit of land^2^, primarily by resource-poor smallholder farmers in developing countries, is recognized as a strategy for soil carbon sequestration (SCS) under the Clean Development Mechanism (CDM) of the Kyoto Protocol^3^. The understanding about C storage and dynamics under agroforestry systems (AFS), however, is minimal. Our studies under various AFS in diverse ecological conditions in five countries showed that tree-based agricultural systems, compared to treeless systems, stored more C in deeper soil layers up to 1 m depth under comparable conditions. More C is stored in soil near the tree than away from the tree; higher SOC content is associated with higher species richness and tree density; and C3 plants (trees) contribute to more C in the silt- + clay-sized (<53 µm) fractions that constitute more stable C, than C4 plants, in deeper soil profiles4 - 8. These results provide clear indications of the possibilities for climate change mitigation through SCS in AFS, and opportunities for economic benefit - through carbon trading - to millions of smallholder farmers in developing countries
Flavour physics constraints in the BMSSM
We study the implications of the presence of the two leading-order,
non-renormalizable operators in the Higgs sector of the MSSM to flavour physics
observables. We identify the constraints of flavour physics on the parameters
of the BMSSM when we: a) focus on a region of parameters for which electroweak
baryogenesis is feasible, b) use a CMSSM-like parametrization, and c) consider
the case of a generic NUHM-type model. We find significant differences as
compared to the standard MSSM case.Comment: 22 pages, 7 figure
Las gotas lĂpidicas nucleares constituyen un nuevo dominio nuclear
Teniendo en cuenta que los lĂpidos neutros nucleares pueden representar pooles alternativos de ácidos grasos y lĂpidos de señalizaciĂłn celular, el objetivo de este trabajo fue dilucidar un modelo de organizaciĂłn de estos lĂpidos neutro
Status of Electroweak Phase Transition and Baryogenesis
I review recent progress on the electroweak phase transition and
baryogenesis, focusing on the minimal supersymmetric standard model as the
source of new physics.Comment: 10 pp, 6 figures; plenary talk given at 6th Workshop on High Energy
Physics Phenomenology, 4 Jan. 2000, Chennai, India. v.2: added reference
Xenoestrogens released from lacquer coatings in food cans
We present data showing that some foods preserved in lacquer-coated cans and the liquid in them may acquire estrogenic activity. Hormonal activity was measured using the E-screen bioassay. The biological activity of vegetables packed in cans was a result of plastic monomers used in manufacturing the containers. The plastic monomer bisphenol-A, identified by mass spectrometry, was found as a contaminant not only in the liquid of the preserved vegetables but also in water autoclaved in the cans. The amount of bisphenol-A in the extracts accounted for all the hormonal activity measured. Although the presence of other xenoestrogens cannot be ruled out, it is apparent that all estrogenic activity in these cans was due to bisphenol-A leached from the lacquer coating. The use of plastic in food-packaging materials may require closer scrutiny to determine whether epoxy resins and polycarbonates contribute to human exposure to xenoestrogens.This work was supported by grant 94/1551
from the Fondo de Investigaciones Sanitarias (FIS), Spanish Ministry of Health
Leptogenesis beyond the limit of hierarchical heavy neutrino masses
We calculate the baryon asymmetry of the Universe in thermal leptogenesis
beyond the usual lightest right-handed (RH) neutrino dominated scenario (N_1DS)
and in particular beyond the hierarchical limit (HL), M_1 << M_2 << M_3, for
the RH neutrino mass spectrum. After providing some orientation among the large
variety of models, we first revisit the central role of the N_1DS, with new
insights on the dynamics of the asymmetry generation and then discuss the main
routes departing from it, focusing on models beyond the HL. We study in detail
two examples of `strong-strong' wash-out scenarios: one with `maximal phase'
and the limit of very large M_3, studying the effects arising when
delta_2=(M_2-M_1)/M_1 is small. We extend analytical methods already applied to
the N_1DS showing, for example, that, in the degenerate limit (DL), the
efficiency factors of the RH neutrinos become equal with the single decay
parameter replaced by the sum. Both cases disprove the misconception that close
RH neutrino masses necessarily lead to a final asymmetry enhancement and to a
relaxation of the lower bounds on M_1 and on the initial temperature of the
radiation-dominated expansion. We also explain why leptogenesis tends to favor
normal hierarchy compared to inverted hierarchy for the left-handed neutrino
masses.Comment: 30 pages, 8 figures; corrected typo in Eq. (67); shortened
Introduction, Section 3 and Conclusions; one figure removed; added 2
references; to appear in JCA
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