21 research outputs found
Two-state behaviour of Kondo trimers
No full textThe electronic properties and spectroscopic features of a magnetic trimer with a Kondo-like coupling to a non-magnetic metallic substrate are analyzed at zero temperature. The substrate density of states is depressed in the trimer neighbourhood, being exactly zero at the substrate chemical potential. The size of the resonance strongly depends on the magnetic state of the trimer, and exhibits a two-state behavior. The geometrical dependence of these results agree qualitatively with recent experiments and could be reproduced in a triangular quantum dot arrangement.Fil: Torio, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Hallberg, Karen Astrid. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Proetto, Cesar Ramon. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentin
Tackling the Challenges of Dynamic Experiments Using Liquid-Cell Transmission Electron Microscopy
No full textConspectusRevolutions in science and engineering frequently result from the development, and wide adoption, of a new, powerful characterization or imaging technique. Beginning with the first glass lenses and telescopes in astronomy, to the development of visual-light microscopy, staining techniques, confocal microscopy, and fluorescence super-resolution microscopy in biology, and most recently aberration-corrected, cryogenic, and ultrafast (4D) electron microscopy, X-ray microscopy, and scanning probe microscopy in nanoscience. Through these developments, our perception and understanding of the physical nature of matter at length-scales beyond ordinary perception have been fundamentally transformed. Despite this progression in microscopy, techniques for observing nanoscale chemical processes and solvated/hydrated systems are limited, as the necessary spatial and temporal resolution presents significant technical challenges. However, the standard reliance on indirect or bulk phase characterization of nanoscale samples in liquids is undergoing a shift in recent times with the realization (Williamson et al. Nat. Mater. 2003, 2, 532-536) of liquid-cell (scanning) transmission electron microscopy, LC(S)TEM, where picoliters of solution are hermetically sealed between electron-transparent "windows," which can be directly imaged or videoed at the nanoscale using conventional transmission electron microscopes. This Account seeks to open a discussion on the topic of standardizing strategies for conducting imaging experiments with a view to characterizing dynamics and motion of nanoscale materials. This is a challenge that could be described by critics and proponents alike, as analogous to doing chemistry in a lightning storm; where the nature of the solution, the nanomaterial, and the dynamic behaviors are all potentially subject to artifactual influence by the very act of our observation
Artichoke Industrial Waste in Durum Wheat Bread: Effects of Two Different Preparation and Drying Methods of Flours and Evaluation of Quality Parameters during Short Storage
No full text'Violetto di Ramacca' is a local variety of artichoke grown in Sicily (Southern Italy), known for its purple color with green streaks. In this study, the effects of two different preparation and drying methods (method A, fresh sample oven-dried at 40 °C for 48 h then mixed and ground into flour; and B, minced and frozen sample oven-dried at 40 °C for 24 h then blended and ground into flour) for flours from different parts of the artichoke (bracts, stems, and mix), used at different percentages of integration (5, 7.5, and 10%), in combination with re-milled semolina, have been evaluated. The polyphenol contents of the flours produced with the two methods were measured. The results showed significant differences between the methods and samples, with a range from 9.09 mg GAE/g d.m. (bracts 100%, method A) to 2.62 mg/g (mix 100%, method B). The values were then lowered in the flour products with supplements ranging from 0.96 mg GAE/g (bract flour 10%, method A) to 0.11 mg GAE/g (mixed flour 7.5%, method B). As the amounts of polyphenols increased, the antioxidant activity increased, with a range that varied in the pure flour from 8.59 mg trolox eq/g d.m. (bract flour, method A) to 3.83 mg trolox eq/g d.m. (mixed flour, method B). These flours were also analyzed for color, highlighting a clear difference between methods A (greener) and B (browner). The flours thus obtained were used to produce breads, which were evaluated for their physicochemical characteristics during 4 days of storage. The results showed a reduction in volumes and heights, an increase in the percentage of integration of the artichoke flours, a greater quantity of moisture in the integrated breads, and a lower reduction in the structural characteristics during storage compared to the control breads. The TPA was conducted on the breads from T0 to T4, highlighting that, although initially more compact, the integrated breads offered less alteration of the values during storage. The aw ranged from 0.63 (mix flour 5%, method B) to 0.90 (bract flour 5%, method B). The amounts of polyphenols (from 0.57 mg GAE/g in bread with bracts at 10% (method A) to 0.13 mg GAE/g in bread with mix 5% (method B)) and the antioxidant activity (from 0.55 mg trolox eq/g d.m. in bread with bract flour 10% (method A) to 0.14% mg trolox eq/g d.m. in bread with mix flour) were also evaluated, showing a trend similar to the values obtained in the flours. Colorimetric tests highlighted a color more similar to wholemeal bread in the loaves produced with method B. Statistical factor analysis and cluster analysis were conducted for all trials
Entwicklung und biologische Studien neuer [Diarylsalen]- und [Salophen]platin(II)-Komplexe mit Antitumoraktivität
No full textThis thesis presents the synthesis and characterization of antitumour active
platinum(II) complexes as well as their physicochemical and biological
properties under in-vitro conditions. Two compounds,
[meso-3,4-bis(4-fluorophenyl)-1,6-bis(2-hydroxyphenyl)-2,5-diaza-
hexa-1,5-diene]platinum(II) and
[N,N -bis(salicylidene)-1,2-phenylenediamine]platinum(II), were chosen as lead
substances for the design of [diarylsalene]- and [salophene]platinum(II)
derivatives. Ligands with structural differences or bearing different
substitutions patterns were prepared in order to investigate the influence of
the ligand structure on the antitumour activity. The cytotoxicity was
evaluated mainly in MCF-7 human breast cancer cells and is presented as IC50
values. Moreover, active substances (IC50 < 20 μM) were tested for their
cytotoxic activity in a time- and concentration-dependent manner. For
compounds of both [diarylsalene]- and [salophene]platinum(II) series IC50
values in a wide concentrations range were calculated. Outstanding cytotoxic
properties demonstrated some [salophene]platinum(II) derivatives, with IC50
values less than 1 μM. Anyhow, neither for the diarylsalene nor for the
salophene series a structure-activity relationship has been found. Concerning
the [diarylsalene]platinum(II) series, results were in general not very
promising since only one compound produced higher antiproliferative effects
than the lead structure. Therefore, further investigations were carried out
only with the [salophene]platinum(II) derivatives. In an attempt to explain
the differences in cytotoxicity between the [salophene]platinum(II)
derivatives, their cellular accumulation was analyzed. All the complexes were
satisfactorily taken up into the tumour cells. Although a correlation between
accumulation grade and cytotoxicity could not be precisely established, the
intracellular drug concentration demonstrated to be strongly influenced by the
nature and the position of the ligand substituents. Physicochemical analysis
included the determination of the lipophilicity and aqueous solubility of the
compounds. The complexes generally presented rather high lipophilicity and low
solubility. While the obtained solubility values showed only in a few cases a
relationship with the analyzed biological properties, lipophilicity seems to
be linearly correlated with IC50 and accumulation values. Considering that
antitumour activity was not directly associated with the intracellular drug
concentration, it is not possible to establish the expected direct
relationship between drug lipophilicity, cellular accumulation and cytotoxic
effect. This suggests that it would be interesting to investigate a possible
direct influence of lipophilicity on the drug-target interaction. Since DNA is
a likely target for anticancer platinum-based coordination compounds, the
[salophene]platinum(II) compounds were analyzed for their interactions with
isolated DNA. Surprisingly, neither intercalation nor DNA binding demonstrated
to be major mechanisms for the cytotoxic activity of the tested platinum
complexes. This suggests that it is possible to exclude DNA as the main target
of the [salophene]platinum(II) complexes. Non-genomic structures, such as
proteins involved in apoptotic processes or proteins related to the
homeostasis of the extracellular matrix, are proposed as possible targets.
Overall, this work provided a great number of novel platinum-based complexes,
potentially active as anticancer agents. It is clear that substituents on the
ligand scaffold can modulate the biological properties of the synthesized
platinum(II) complexes. Understanding their antitumour mechanism of action and
target still remains as an important challenge in order to generate
functionalised complexes with optimized physicochemical and biological
properties.Diese Arbeit stellt die Synthese und Charakterisierung von antitumor-aktiven
Platin(II)-Komplexen sowie deren physikochemischen und biologischen
Eigenschaften unter in-vitro Bedingungen vor. Zwei Verbindungen,
[meso-3,4-Bis(4-fluorphenyl)-1,6-bis(2-hydroxyphenyl)-2,5-diazahexa-1,5-dien]platin(II)
und [N,N'-Bis(salicyliden)-1,2-phenylendiamin]platin(II), wurden jeweils als
Leitsubstanzen für die [Diarylsalen]- und [Salophen]platin(II)- Derivate
ausgewählt. Liganden mit strukturellen Unterschieden oder verschiedenen
Substitutionsmustern wurden vorbereitet, um den Einfluss ihrer Struktur auf
die Antitumor-Aktivität zu untersuchen. Die Zytotoxizität wurde vor allem in
MCF-7 Brustkrebszellen ausgewertet und als IC50-Werte präsentiert. Darüber
hinaus wurden in Abhängigkeit von Zeit und Konzentration - Wirkstoffe (IC50
<20 μM) auf ihre zytotoxische Aktivität geprüft. In beiden Serien, der
[Diarylsalen]- und der [Salophen]platin(II)-Serie, wurden Verbindungen mit
IC50-Werten in einem großen Konzentration-Bereich nachgewiesen. Besonders
einige [Salophen]platin(II)-Derivate wiesen herausragende zytotoxische
Eigenschaften auf, mit IC50-Werten von weniger als 1 μM. Es wurde jedoch weder
für die Diarylsalen- noch für die Salophen-Serie eine Struktur-Wirkungs-
Beziehung gefunden. In Bezug auf die [Diarylsalen]platin(II)-Serie waren die
Ergebnisse generell nicht sehr vielversprechend, da nur eine Verbindung eine
signifikante Erhöhung der antiproliferativen Effekte im Vergleich zu der
Leitstruktur bewirkte. Daher wurden weitere Untersuchungen nur mit den
[Salophen]platin(II)-Derivaten durchgeführt. Um die Unterschiede in der
Zytotoxizität zwischen den [Salophen]platin(II)-Derivaten zu erklären, wurde
ihre zelluläre Akkumulation analysiert. Alle Komplexe erwiesen sich als in den
Tumorzellen gut aufnehmbar. Obwohl eine Korrelation zwischen Akkumulations-
Werten und Zytotoxizität nicht genau festgestellt werden konnte, wurde
aufgezeigt, dass die intrazelluläre Wirkstoffkonzentration stark von der Natur
und der Position der Liganden-Substituenten beeinflusst wird. Mittels
physikochemischer Analyse wurden Lipophilie und Wasserlöslichkeit der
Verbindungen bestimmt. Die Komplexe wiesen grundsätzlich ziemlich hohe
Lipophilie und eine geringe Löslichkeit auf. Während die Löslichkeitswerte nur
in wenigen Fällen einen Zusammmenhang mit den analysierten biologischen
Eigenschaften zeigten, scheint Lipophilie linear mit IC50 und Akkumulation
korreliert zu sein. In Anbetracht dessen, dass Antitumor-Aktivität mit der
intrazellulären Wirkstoffkonzentration nicht unmittelbar assoziiert war, lässt
sich kein direkter Zusammenhang zwischen Lipophilie, zellulärer Akkumulation
und zytotoxischer Wirkung begründen. Weiterführend wäre es interessant, einen
möglichen unmittelbaren Einfluss der Lipophilie auf die Drug-
Target -Wechselwirkung zu untersuchen. Da die DNA als ein Ziel für Platin-
basierte Anti-Krebs-Wirkstoffe galt, wurden die
[Salophen]platin(II)-Verbindungen auf ihre Wechselwirkungen mit isolierten DNA
analysiert. Überraschenderweise erwiesen sich weder Interkalation noch DNA-
Bindung als wesentliche Mechanismen für die zytotoxische Aktivität der
untersuchten Platin-Komplexe. Dies bedeutet, dass die DNA als Hauptziel der
[Salophen]platin(II)-Komplexe ausgeschlossen werden kann. Stattdessen werden
nicht-genomische Strukturen, wie in apoptotischen Prozessen beteiligte
Proteine oder Proteine im Zusammenhang mit der Homöostase der extrazellulären
Matrix vorgeschlagen. Insgesamt wurde in dieser Arbeit eine große Anzahl von
neuen Platin-Komplexen, als potentielle Antikrebs-Wirkstoffe identifiziert.
Substituenten am Liganden-Gerüst können die biologischen Eigenschaften der
synthetischen Platin(II)-Komplexe modulieren. Es bleibt als große
Herausforderung, ihren Antitumor-Wirkungsmechanismus und ihre Target zu
verstehen, um funktionalisierte Komplexe mit optimierten physikochemischen und
biologischen Eigenschaften zu generieren
Soft nanomaterials analysed by in situ liquid TEM: Towards high resolution characterisation of nanoparticles in motion
No full textSummaryIn this article we present in situ transmission electron microscopy (TEM) of soft, synthetic nanoparticles with a comparative analysis using conventional TEM methods. This comparison is made with the simple aim of describing what is an unprecedented example of in situ imaging by TEM. However, we contend the technique will quickly become essential in the characterisation of analogous systems, especially where dynamics are of interest in the solvated state. In this case, particles were studied which were obtained from the direct polymerisation of an oxaliplatin analogue, designed for an ongoing programme in novel chemotherapeutic delivery systems. The resulting nanoparticles provided sufficient contrast for facile imaging in situ, and point towards key design parameters that enable this new characterisation approach for organic nanomaterials. We describe the preparation of the synthetic nanoparticles together with their characterisation in liquid water. Finally, we provide a future perspective of this technique for the analysis of soft and dynamic nanomaterials and discussion the progress which needs to be made in order to bring in situ liquid TEM to its full potential
Synthesis, Characterization, and in vitro Antiproliferative Activity of [Salophene]platinum(II) Complexes
No full text
NHC Gold Halide Complexes Derived from 4,5-Diarylimidazoles: Synthesis, Structural Analysis, and Pharmacological Investigations as Potential Antitumor Agents
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