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1.
J Chem Theory Comput ; 20(5): 1972-1987, 2024 Mar 12.
Artículo en Inglés | MEDLINE | ID: mdl-38324673

RESUMEN

The total energy and electron addition and removal spectra can, in principle, be obtained exactly from the one-body Green's function (GF). In practice, the GF is obtained from an approximate self-energy. In the framework of many-body perturbation theory, we derive different expressions that are based on an approximate self-energy, but that yield nevertheless, in principle, the exact exchange-correlation contribution to the total energy for any interaction strength. Response functions play a crucial role, which explains why, for example, ingredients from time-dependent density functional theory can be used to build these approximate self-energies. We show that the key requirement for obtaining exact results is the consistent combination of ingredients. Also when further approximations are made, as it is necessary in practice, this consistency remains the key to obtain good results. All findings are illustrated using the exactly solvable symmetric Hubbard dimer.

2.
PeerJ ; 12: e16839, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-38348103

RESUMEN

Hieracium lucidum subsp. lucidum is a critically endangered endemic taxa of the Sicilian flora. It is a relict of the Tertiary period surviving on the cliffs of Monte Gallo (NW-Sicily). This research focused on finding the best protocols for seed germination and vegetative and in vitro propagation to contribute to ex situ conservation. Seed germination tests were carried out using constant temperatures of 15 °C, 20 °C and 25 °C in continuous darkness and an alternating temperature of 30/15 °C (16 h/8 h, light/dark). The seeds had no dormancy, and a high germination capacity (70-95%) was obtained at all tested thermoperiods. The possibility of vegetative propagation of the taxon was evaluated through the rooting capacity of stem cuttings treated or not treated with indole-3-butyric acid (IBA). All cuttings were treated with IBA rooted within 2 months, while only 50% of the untreated cuttings were rooted within a longer time. An efficient protocol for rapid in vitro propagation from leaf portions was developed. The response of explants was tested on hormone-free Murashige and Skoog (MS) basal medium and MS enriched with different types of cytokinins: 6-Benzylaminopurine (BAP) and meta-Topolin (mT) in combination with naphthaleneacetic acid (NAA) and 2,4-Dichlorophenoxyacetic acid (2,4-D) at the same concentration. The combination of mT (2 mg L-1) and 2,4-D (1 mg L-1) in the medium was the most effective and showed the highest percentage of callus induction and the mean number of regenerated shoots. The maximum rate of root regeneration and the maximum number and length of roots were obtained on hormone-free MS and MS enriched with IBA at concentrations of 1 mg L-1. From the results obtained, it can be concluded that H. lucidum subsp. lucidum can be successfully propagated using one of the tested techniques, subject to the availability of the material for reproduction.


Asunto(s)
Asteraceae , Germinación , Germinación/fisiología , Semillas , Citocininas , Ácido 2,4-Diclorofenoxiacético
3.
Phys Chem Chem Phys ; 26(5): 4363-4371, 2024 Jan 31.
Artículo en Inglés | MEDLINE | ID: mdl-38235804

RESUMEN

Inelastic X-ray scattering (IXS) spectroscopy has been used in many fields of solid-state physics and theoretical chemistry as an accurate and quantitative probe of elementary excitations. We show that non-resonant IXS spectra in the energy loss range below 100 eV exhibit a strong contrast across a wide range of commercially available pigments, opening new routes for their discrimination. These signatures combine plasmonic transitions, collective excitations and low energy absorption edges. We have performed IXS to discriminate different artists' pigments within complex mixtures and to quantitatively determine rutile and anatase polymorphs of TiO2. The integration of experimental data on pigment powders with suitable ab initio simulations shows a precise fit of the spectroscopic data both in the position of the resonances and in their relative intensity.

4.
Nat Prod Res ; : 1-9, 2023 Nov 01.
Artículo en Inglés | MEDLINE | ID: mdl-37909244

RESUMEN

In this work the mucilage obtained from the cladodes of a not previously investigated accession of Opuntia stricta (Haw.) Haw. (syn. Opuntia dillenii (Ker-Gawl) Haw), collected in Sicily, was analysed by 13C-NMR. The yield of mucilage extracted from cladodes in aqueous medium was 2.55%. The monosaccharides identified, after acidic hydrolyses of the mucilage, were arabinose (36.48%), galactose (32.31%), xylose (15.33%), glucose (10.45%) and rhamnose (5.40%). The mucilage showed a sufficient antimicrobial activity and excellent antioxidant property.

5.
Plants (Basel) ; 12(7)2023 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-37050156

RESUMEN

The conservation of endangered, rare, and endemic plant species is based on in situ and ex situ conservation strategies. When in situ conservation alone is not sufficient to guarantee the survival of the species, ex situ techniques are adopted in support. This study aimed to develop an efficient micropropagation protocol for Adenostyles by evaluating the effect of different plant growth regulators on leaf explants. Adenostyles alpina subsp. macrocephala (Asterace) is a perennial herbaceous plant endemic to Calabria (Southern Italy). The genus Adenostyles includes three species confined to the mountains of the Mediterranean and southern Europe. For callus induction, media supplemented with different concentrations of Benzylaminopurine (BAP) (0.5, 1, 2, and 3 mg L-1), Naphthaleneacetic Acid (NAA) (1 mg L-1), and 2,4-Dichlorophenoxyacetic Acid (2,4-D) (1 mg L-1) were tested. Shoot regeneration and proliferation were obtained in media supplemented with BAP (1, 2, and 3 mg L-1) and NAA (1 mg L-1). Root induction was obtained in media supplemented with IBA (0.25, 0.50, and 1 mg L-1) and NAA (0.25, 0.50, and 1 mg L-1). Statistically significant differences in callus induction and shoot regeneration were observed between the various media tested. The medium containing Murashige and Skoog (MS) supplemented with 3 mg L-1 of BAP and 1 mg L-1 of NAA showed the highest percentage of callus induction and increased shoot regeneration. The regenerated shoots showed more effective root induction in the hormone-free MS medium and in the presence of Indole-3-Butyric Acid (IBA) at concentrations of 0.25, 0.50, and 1 mg L-1. These results can be used as a basis for the preparation of a micropropagation protocol for different taxa of Adenostyles, as well as other species of Asteraceae specialized to the Mediterranean mountain habitat.

6.
Int J Food Microbiol ; 395: 110194, 2023 Jun 16.
Artículo en Inglés | MEDLINE | ID: mdl-37004495

RESUMEN

Almond production generates large amounts of by-products rich in polyphenols. In this study, almond skin was explored as a valuable food ingredient in bread making. To this purpose, almond skin was used to produce functional products modifying a traditional sourdough bread recipe. The doughs were prepared replacing semolina with powdered almond skin (PAS) at 5 and 10 % (w/w). Sourdough inoculum was started with a mix of lactic acid bacteria (LAB) and propagated in semolina until reaching pH 3.7. The pH of PAS added breads was higher than that of control (CTR) breads before and after fermentation. Plate counts showed a similar evolution of LAB and total mesophilic microorganisms, but members of Enterobacteriaceae and coliform were detectable in PAS doughs. Illumina data clearly showed a dominance of lactobacilli in all trials, but PAS doughs displayed the presence of Bacillus. The final bread characteristics were influenced by PAS and its addition percentage; in particular, crust and crumb colour resulted darker, the alveolation decreased and, regarding sensory attributes, odour intensity increased, while bread odour diminished. In presence of PAS, bread emissions were characterized by lower percentages of alcohols and aromatic hydrocarbons and higher percentages of the other volatile compound classes, especially terpenoids like ß-pinene, ß-myrcene and limonene than CTR trial. After in vitro simulated digestion, the final release of phytochemicals from 10 % PAS bread was almost 100 %. Thus, PAS determined an increase of the antioxidant capacity of the breads. Phytochemicals released from digested PAS-fortified bread can provide antioxidant protection in a complex biological environment such as human intestinal-like cells. Besides the positive functional properties of PAS, this work also evidenced the hygienic issues of almond skin and, in order to avoid potential risks for the human health, highlighted the need to preserve its microbiological characteristics during storage for their reuse in bread production.


Asunto(s)
Lactobacillales , Prunus dulcis , Humanos , Pan/microbiología , Antioxidantes , Lactobacillus , Triticum/microbiología , Fermentación , Grano Comestible
7.
Foods ; 12(5)2023 Mar 05.
Artículo en Inglés | MEDLINE | ID: mdl-36900625

RESUMEN

A new accession of myrobalan (Prunus cerasifera L.) from Sicily (Italy) was studied for the first time for its chemical and nutraceutical properties. A description of the main morphological and pomological traits was created as a tool for characterization for consumers. For this purpose, three different extracts of fresh myrobalan fruits were subjected to different analyses, including the evaluation of total phenol (TPC), flavonoid (TFC), and anthocyanin (TAC) contents. The extracts exhibited a TPC in the range 34.52-97.63 mg gallic acid equivalent (GAE)/100 g fresh weight (FW), a TFC of 0.23-0.96 mg quercetin equivalent (QE)/100 g FW, and a TAC of 20.24-55.33 cyanidine-3-O-glucoside/100 g FW. LC-HRMS analysis evidenced that the compounds mainly belong to the flavonols, flavan-3-ols, proanthocyanidins, anthocyanins, hydroxycinnamic acid derivatives, and organic acids classes. A multitarget approach was used to assess the antioxidant properties by using FRAP, ABTS, DPPH, and ß-carotene bleaching tests. Moreover, the myrobalan fruit extracts were tested as inhibitors of the key enzymes related to obesity and metabolic syndrome (α-glucosidase, α-amylase, and lipase). All extracts exhibited an ABTS radical scavenging activity that was higher than the positive control BHT (IC50 value in the range 1.19-2.97 µg/mL). Moreover, all extracts showed iron-reducing activity, with a potency similar to that of BHT (53.01-64.90 vs 3.26 µM Fe(II)/g). The PF extract exhibited a promising lipase inhibitory effect (IC50 value of 29.61 µg/mL).

8.
Nat Prod Res ; 37(10): 1680-1686, 2023 May.
Artículo en Inglés | MEDLINE | ID: mdl-35876171

RESUMEN

In this study, almond skin of Prunus dulcis L. variety Casteltermini was characterised for its chemical composition and for the inhibitory activity towards food associated microorganisms belonging to pathogenic (Salmonella Enteritidis, Staphylococcus aureus, Escherichia coli and Listeria monocytgenes), spoilage (Pseudomonas poae and Brochotrix thermospacta) and useful (Levilactobacillus brevis and Saccharomyces cerevisiae) groups. The n-hexane extract of P. dulcis skin, investigated by GC-MS, evidenced linoleic, palmitic, and oleic acids as the main abundant compounds. Staphylococcus aureus ATCC 33862 growth was strongly limited by n-hexane extract and the minimum inhibition concentration (MIC) was 25.5 mg/mL. These results highlight the potential of almond by-products as food bio-preservatives as well as pharmaceutical products.


Asunto(s)
Prunus dulcis , Prunus dulcis/química , Antibacterianos/farmacología , Pruebas de Sensibilidad Microbiana , Staphylococcus aureus
9.
Phys Chem Chem Phys ; 24(29): 17439-17448, 2022 Jul 27.
Artículo en Inglés | MEDLINE | ID: mdl-35708135

RESUMEN

We present a formalism for the resonant inelastic X-ray scattering (RIXS) cross section. The resulting compact expression in terms of polarizability matrix elements, particularly lends itself to the implementation in an all-electron many-body perturbation theory (MBPT) framework, which is realized in the full-potential package exciting. With the carbon K edge RIXS of diamond and the oxygen K edge RIXS of ß-Ga2O3, respectively, we demonstrate the importance of electron-hole correlation and atomic coherence in the RIXS spectra.

10.
Foods ; 11(7)2022 Mar 30.
Artículo en Inglés | MEDLINE | ID: mdl-35407095

RESUMEN

The public catering sector has important responsibilities in seeking a change toward more sustainable choices for many aspects related to the environmental impacts of their services. The environmental impact of production processes can be studied through life cycle assessment (LCA), which allows a greater awareness of choices and has rarely been applied to catering. In this work, we studied the impacts of two dishes (braised meat and cauliflower meatballs) in a school canteen, their impacts were studied using the daily energy requirement (expressed in kcal) as a functional unit. Global warming potential (GWP) and nonrenewable energy (NRE) were calculated starting from the supply of raw materials up to distribution. Electricity and the act of cooking the meatballs accounted for more than 60% of the measured impact in terms of GWP, whereas, less markedly, they dominated in terms of nonrenewable energy used. In the case of braised meat, the total impact was, however, attributable to the life cycle of the meat (between 60% and 76%) and the consumption of electricity (between 19% and 27%), whereas for all other factors, the contribution was never particularly high. Additionally, a discussion on the correct functional unit to be used proposed the environmental impact of different recipes as an additional criterion for nutritionists during the composition of the menu. An integrated system appears important for changing policies and behaviors and the application of LCA can be a tool capable of contributing to the construction of a holistic instrument of sustainability.

11.
Plants (Basel) ; 11(4)2022 Feb 14.
Artículo en Inglés | MEDLINE | ID: mdl-35214852

RESUMEN

The genus Crepis L., included within the Asteraceae family, has a very wide distribution, expanding throughout the northern hemisphere, including Europe, northern Africa, and temperate Asia. This genus has a fundamental value from biodynamic and ecological perspectives, with the different species often being chosen for soil conservation, for environmental sustainability, and for their attraction towards pollinating species. Furthermore, various species of Crepis have been used in the popular medicine of several countries as medicinal herbs and food since ancient times. In most cases, the species is consumed either in the form of a decoction, or as a salad, and is used for its cardiovascular properties, as a digestive, for problems related to sight, for the treatment of diabetes, and for joint diseases. This literature review, the first one of the Crepis genus, includes publications with the word 'Crepis', and considers the single metabolites identified, characterised, and tested to evaluate their biological potential. The various isolated compounds, including in most cases sesquiterpenes and flavonoids, were obtained by extracting the roots and aerial parts of the different species. The secondary metabolites, extracted using traditional (solvent extraction, column chromatography, preparative thin layer chromatography, preparative HPLC, vacuum liquid chromatography), and modern systems such as ultrasounds, microwaves, etc., and characterised by mono- and bi- dimensional NMR experiments and by HPLC-MS, have a varied application spectrum at a biological level, with antimicrobial, antioxidant, antidiabetic, antitumor, antiviral, antiulcer, phytotoxic, and nutritional properties having been reported. Unfortunately, in vitro tests have not always been accompanied by in vivo tests, and this is the major critical aspect that emerges from the study of the scientific aspects related to this genus. Therefore, extensive investigations are necessary to evaluate the real capacity of the different species used in food, and above all to discover what the different plants that have never been analysed could offer at a scientific level.

12.
Antioxidants (Basel) ; 12(1)2022 Dec 22.
Artículo en Inglés | MEDLINE | ID: mdl-36670885

RESUMEN

Polymethoxyflavonoids (PMFs) are a large group of compounds belonging to the more general class of flavonoids that possess a flavan carbon framework decorated with a variable number of methoxy groups. Hydroxylated polymethoxyflavonoids (HPMFs), instead, are characterized by the presence of both hydroxyl and methoxy groups in their structural unities. Some of these compounds are the aglycone part in a glycoside structure in which the glycosidic linkage can involve the -OH at various positions. These compounds are particular to Citrus genus plants, especially in fruits, and they are present mainly in the peel. A considerable number of PMFs and HPMFs have shown promising biological activities and they are considered to be important nutraceuticals, responsible for some of the known beneficial effects on health associated with a regular consumption of Citrus fruits. Among their several actions on human health, it is notable that the relevant contribution in controlling the intracellular redox imbalance is associated with the inflammation processes. In this work, we aim to describe the status concerning the chemical identification and the anti-inflammatory activity of both PMFs and HPMFs. In particular, all of the chemical entities unambiguously identified by isolation and complete NMR analysis, and for which a biochemical evaluation on the pure compound was performed, are included in this paper.

13.
Antioxidants (Basel) ; 10(8)2021 Jul 29.
Artículo en Inglés | MEDLINE | ID: mdl-34439465

RESUMEN

This work proposes for the first time a model for reusing almond (Prunus dulcis cv. Casteltermini from Sicily, Southern Italy) skin to formulate a new functional blackberry (Rubus ulmifolius Schott) jam. For this purpose, blackberries were analysed fresh and as jam, traditionally prepared with a minimum fruit amount of 80%. Different percentages of almond skin (20, 15, and 10% w/w) were added to jam. The phytochemical profile of enriched jam was investigated by LC-ESI/LTQOrbitrap/MS analyses. Anthocyanins, hydrolysable tannins, and triterpenoids were identified in a blackberry extract, while proanthocyanidins, flavonoids, and oxylipins were identified in an almond extract. The n-hexane extract of P. dulcis skin, investigated by GC-MS, evidenced linoleic, palmitic, and oleic acids as the main abundant compounds. Samples were investigated for their antioxidant activity using DPPH, ABTS, ß-carotene, and FRAP tests. The hypoglycaemic and hypolipidemic effects were studied by α-amylase, α-glucosidase, and lipase inhibitory assays. In order to evaluate the effect of thermal process on enriched jam bioactivity, pasteurisation was applied. An increase in activities for all samples was observed, in particular for jam enriched with 20% w/w of almond skin. Based on obtained data, and supported by sensory analysis, we propose enriched jam as a promising source of compounds useful for preventing diseases associated with oxidative stress.

14.
Polymers (Basel) ; 13(16)2021 Aug 09.
Artículo en Inglés | MEDLINE | ID: mdl-34451182

RESUMEN

This study explores the processability, mechanical, and thermal properties of biocompostable composites based on poly (butylene adipate-co-terephthalate) (PBAT) as polymer matrix and microcrystalline cellulose (MCC) derived from softwood almond (Prunus dulcis) shells (as-MCC) as filler at two different weight concentration, i.e., 10 wt% and 20 wt%. The materials were processed by melt mixing and a commercial MCC (c-MCC) was used as filler comparison. The fibrillar shape of as-MCC particles was found to change the rheological behavior of PBAT, particularly at the highest concentration. The melt mixing processing allowed obtaining a uniform dispersion of both kinds of fillers, slightly reducing the L/D ratio of as-MCC fibers. The as-MCC particles led to a higher increase of the elastic modulus of PBAT if compared to the c-MCC counterparts. Both the MCC fillers caused a drastic reduction of the elongation at break, although it was higher than 120% also at the highest filler concentrations. DSC analysis revealed that both MCC fillers poorly affected the matrix crystallinity, although as-MCC induced a slight PBAT crystallinity increase from 8.8% up to 10.9% for PBAT/as-MCC 20%. Therefore, this work demonstrates the great potential of MCC particles derived from almond shells as filler for biocompostable composites fabrication.

15.
Mol Cell ; 81(15): 3065-3081.e12, 2021 08 05.
Artículo en Inglés | MEDLINE | ID: mdl-34297911

RESUMEN

The chromatin fiber folds into loops, but the mechanisms controlling loop extrusion are still poorly understood. Using super-resolution microscopy, we visualize that loops in intact nuclei are formed by a scaffold of cohesin complexes from which the DNA protrudes. RNA polymerase II decorates the top of the loops and is physically segregated from cohesin. Augmented looping upon increased loading of cohesin on chromosomes causes disruption of Lamin at the nuclear rim and chromatin blending, a homogeneous distribution of chromatin within the nucleus. Altering supercoiling via either transcription or topoisomerase inhibition counteracts chromatin blending, increases chromatin condensation, disrupts loop formation, and leads to altered cohesin distribution and mobility on chromatin. Overall, negative supercoiling generated by transcription is an important regulator of loop formation in vivo.


Asunto(s)
Proteínas de Ciclo Celular/metabolismo , Cromatina/química , Cromatina/genética , Proteínas Cromosómicas no Histona/metabolismo , Transcripción Genética/fisiología , Proteínas de Ciclo Celular/química , Proteínas de Ciclo Celular/genética , Línea Celular , Núcleo Celular/genética , Proteoglicanos Tipo Condroitín Sulfato/genética , Proteoglicanos Tipo Condroitín Sulfato/metabolismo , Cromatina/metabolismo , Proteínas Cromosómicas no Histona/química , Proteínas Cromosómicas no Histona/genética , ADN-Topoisomerasas de Tipo I/genética , ADN-Topoisomerasas de Tipo I/metabolismo , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Femenino , Humanos , Laminas/genética , Laminas/metabolismo , ARN Polimerasa II/metabolismo , Imagen Individual de Molécula/métodos , Cohesinas
16.
Front Nutr ; 8: 659378, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-34150827

RESUMEN

Almond cultivation in Sicily is experiencing a phase of great interest which is mainly concentrated in the development of specialized orchards, with irrigation and by adopting cultivars with high qualitative and quantitative performances. These are mostly Mediterranean genotypes with high fat content and hard or semi-hard shell, extremely different from the varieties of Californian diffusion. The development of the sector comprises the primary production of almonds but also a series of secondary products which often represent a burden for the company. From these considerations several researches have been developed with the aim of giving a value to these by-products through circular economy paths. One of the by-products widely produced, besides the shell, is the skin which covers the seed and is produced during the peeling phase. It is well-known that tegument is an important component of almond because it contains important bioactive substances (phenols and aromas) which are usually dispersed during peeling. This paper examined three different Italian cultivars widely spread in Sicily, two of Apulian origin, (Genco and Tuono), and one locally cultivated variety (Vinci a tutti). These three cultivars occupy an increasingly large area and are very popular with consumers and industry. The production of secondary products, therefore, evidences significant quantities and the possibility to give them an added value becomes a need for the sector. Therefore, the content of phenols and proanthocyanins in the skin at harvest and during storage was analyzed, adopting two different separation methods, with and without water. During the analysis it was possible to observe the different behavior of the three cultivars due to genetic and industrial factors. Skin separated without using hot water showed a higher total phenolic presence with average increases of about 20%, and with even higher increases, between 28 and 32%, for proanthocyanins. Vinci a tutti evidenced the highest total phenolic content after 8 months of storing while roasting has revealed to be a more effective skin separation approach.

17.
Artículo en Inglés | MEDLINE | ID: mdl-33671320

RESUMEN

Previous research has suggested that activities such as community gardens could offer a wide range of health benefits. The aim of the article is to systematically review the available literature to analyse the magnitude of the phenomenon, the geographical distribution, and the main characteristics in terms of health outcomes and target populations. The search addresses the question whether the activity in community gardens improves health and well-being outcomes of individuals. From the total amount of 7226, 84 selected articles showed that:(1) up to 50% are published by U.S. universities or institutions; (2) up to 44% of the studies considered "community gardens" as the main activity of the research focus; (3) one-third of the studies included adults; (4) almost 25% of the studies used "general health" as the main outcome when investigating the benefits of community gardens; (5) the percentage of studies that achieved their outcomes was heterogeneous among the different health dimensions. In conclusion, while a certain degree of heterogeneity in the used definition and outcome still exist, community gardens may be a viable strategy for well-being promotion in terms of psychological, social, and physical health and may be considered as an innovative urban strategy to promote urban public health.


Asunto(s)
Jardinería , Jardines , Adulto , Humanos , Salud Urbana
18.
Nat Prod Res ; 35(3): 359-368, 2021 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-31219358

RESUMEN

Cellulosic fibres have been obtained by green procedures from the cladodes of Opuntia ficus indica (L.) Mill., constituting a large agro industrial waste in our territory. The materials have been analysed for its relative composition, applying, IR and TG methodologies and it was characterised by the absence of lignin. The fibrous material allowed the manufacture of a handmade paper obtaining an ecological material suitable for packaging purposes. The authors evidenced that the simple protocol based on hot water treatment was able to decrease the amount of hemicellulose in the final material.


Asunto(s)
Opuntia/química , Papel , Residuos , Lignina/química , Polisacáridos/química , Sicilia , Espectroscopía Infrarroja por Transformada de Fourier , Termogravimetría
19.
Faraday Discuss ; 224(0): 424-447, 2020 Dec 04.
Artículo en Inglés | MEDLINE | ID: mdl-32930319

RESUMEN

The Kohn-Sham system is the prototypical example of an auxiliary system that targets, in principle exactly, an observable like the electronic density without the need to calculate the complicated many-body wavefunction. Although the Kohn-Sham system does not describe excited-state properties directly, it also represents a very successful strategy guideline for many spectroscopy applications. Here we propose a generalization of the Kohn-Sham idea. In many situations one is interested only in limited answers to specific questions, whereas in state-of-the-art approaches a lot of information is generally calculated that is not needed for the interpretation of experimental spectra. For example, when the target is a spectrum S(ω) like the optical absorption of a solid, within time-dependent density-functional theory (TDDFT) one calculates the whole response function χ(r,r',ω). Analogously, within many-body perturbation theory (MBPT) one calculates the whole one-particle Green's function G(r,r',ω), while only the total spectral function A(ω) is needed for angle-integrated photoemission spectra. In this contribution, we advocate the possibility of designing auxiliary systems with effective potentials or kernels that target only the specific spectral properties of interest and are simpler than the self-energy of MBPT or the exchange-correlation kernel of TDDFT. In particular, we discuss the fundamentals and prototypical applications of simplified effective kernels for optical absorption and spectral potentials for photoemission, and we discuss how to express these potentials or kernels as functionals of the density.

20.
Stem Cell Reports ; 15(3): 646-661, 2020 09 08.
Artículo en Inglés | MEDLINE | ID: mdl-32822589

RESUMEN

The Wnt/ß-catenin signaling pathway is a key regulator of embryonic stem cell (ESC) self-renewal and differentiation. Constitutive activation of this pathway has been shown to increase mouse ESC (mESC) self-renewal and pluripotency gene expression. In this study, we generated a novel ß-catenin knockout model in mESCs to delete putatively functional N-terminally truncated isoforms observed in previous knockout models. We showed that aberrant N-terminally truncated isoforms are not functional in mESCs. In the generated knockout line, we observed that canonical Wnt signaling is not active, as ß-catenin ablation does not alter mESC transcriptional profile in serum/LIF culture conditions. In addition, we observed that Wnt signaling activation represses mESC spontaneous differentiation in a ß-catenin-dependent manner. Finally, ß-catenin (ΔC) isoforms can rescue ß-catenin knockout self-renewal defects in mESCs cultured in serum-free medium and, albeit transcriptionally silent, cooperate with TCF1 and LEF1 to inhibit mESC spontaneous differentiation in a GSK3-dependent manner.


Asunto(s)
Diferenciación Celular , Autorrenovación de las Células , Factor Nuclear 1-alfa del Hepatocito/metabolismo , Factor de Unión 1 al Potenciador Linfoide/metabolismo , Células Madre Embrionarias de Ratones/citología , Vía de Señalización Wnt , beta Catenina/metabolismo , Alelos , Animales , Biomarcadores/metabolismo , Proteína 9 Asociada a CRISPR/metabolismo , Sistemas CRISPR-Cas/genética , Diferenciación Celular/genética , Autorrenovación de las Células/genética , Células Cultivadas , Ectodermo/metabolismo , Endodermo/metabolismo , Ratones , Ratones Noqueados , Células Madre Embrionarias de Ratones/metabolismo , Isoformas de Proteínas/metabolismo , Transcriptoma/genética , Regulación hacia Arriba/genética
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