Unveiling interactions between DNA and cytotoxic 2-arylpiperidinyl-1,4-naphthoquinone derivatives: A combined electrochemical and computational study

Indexación: Scopus.Three 2-arylpiperidinyl-1,4-naphthoquinone derivatives were synthesized and evaluated in vitro to determine their cytotoxicity on cancer and normal cell lines. In order to establish their possible action mechanism, the electrochemical behaviour of these quinones was examined using cyclic voltammetry (CV) as technique by using a three-electrode setup: a glassy carbon, Ag/AgCl (in 3 M KCl), and platinum wire as working, reference, and counter electrodes, respectively. Kinetic studies were done to determine the control of the reduction reaction and the number of transferred electrons in the process. Furthermore, the addition of dsDNA to the quinone solutions allowed for the observation of an interaction between each quinone and dsDNA as the current-peaks became lower in presence of dsDNA. Otherwise, motivated to support the aforementioned results, electronic structure calculations at the TPSS-D3/6-31+G(d,p) level of theory were carried out in order to find the most favourable noncovalently bonded complexes between quinones and DNA. Noncovalent complexes formed between DNA and 2-arylpiperidinyl-1,4-naphthoquinones and stabilized by π-stacking interactions along with the well-known hydrogen-bonded complexes were found, with the former being more stable than the latter. These results suggest that the intercalation of these quinone derivatives in DNA is the most likely action mechanism. © 2018 King Saud Universityhttps://www.sciencedirect.com/science/article/pii/S1878535218300893?via%3Dihu

Temperature - pressure phase diagram of CeCoSi: Pressure induced high-temperature phase

We have studied the temperature-pressure phase diagram of CeCoSi by electrical-resistivity experiments under pressure. Our measurements revealed a very unusual phase diagram. While at low pressures no dramatic changes and only a slight shift of the Ne\'{e}l temperature $T_N$ ($\approx 10$ K) are observed, at about 1.45 GPa a sharp and large anomaly, indicative of the opening of a spin-density-wave (SDW) gap, appears at a comparatively high temperature $T_S \approx 38$ K. With further increasing pressure $T_S$ shifts rapidly to low temperatures and disappears at about 2.15 GPa, likely continuously in a quantum critical point, but without evidence for superconductivity. Even more surprisingly, we observed a clear shift of $T_S$ to higher temperatures upon applying a magnetic field. We discuss two possible origins for $T_S$, either magnetic ordering of Co or a meta-orbital type of transition of Ce.Comment: 6 pages, 5 figure

Remarkable magnetostructural coupling around the magnetic transition in CeCo0.85_{0.85}Fe0.15_{0.15}Si

We report a detailed study of the magnetic properties of CeCo$_{0.85}$Fe$_{0.15}$Si under high magnetic fields (up to 16 Tesla) measuring different physical properties such as specific heat, magnetization, electrical resistivity, thermal expansion and magnetostriction. CeCo$_{0.85}$Fe$_{0.15}$Si becomes antiferromagnetic at $T_N \approx$ 6.7 K. However, a broad tail (onset at $T_X \approx$ 13 K) in the specific heat precedes that second order transition. This tail is also observed in the temperature derivative of the resistivity. However, it is particularly noticeable in the thermal expansion coefficient where it takes the form of a large bump centered at $T_X$. A high magnetic field practically washes out that tail in the resistivity. But surprisingly, the bump in the thermal expansion becomes a well pronounced peak fully split from the magnetic transition at $T_N$. Concurrently, the magnetoresistance also switches from negative to positive just below $T_X$. The magnetostriction is considerable and irreversible at low temperature ($\frac {\Delta L}{L} \left(16 T\right) \sim$ 4$\times$10$^{-4}$ at 2 K) when the magnetic interactions dominate. A broad jump in the field dependence of the magnetostriction observed at low $T$ may be the signature of a weak ongoing metamagnetic transition. Taking altogether, the results indicate the importance of the lattice effects in the development of the magnetic order in these alloys.Comment: 5 pages, 6 figure

Valence fuctuation and magnetic ordering in EuNi2(P1-xGex)2 single crystals

Unusual phases and phase transitions are seen at the magnetic-nonmagnetic boundary in Ce, Eu and Yb-based compounds. EuNi$_2$P$_{2}$ is a very unusual valence fluctuating Eu system, because at low temperatures the Eu valence stays close to 2.5 instead of approaching an integer value. Eu valence and thus the magnetic property in this system can be tuned by Ge substitution in P site as EuNi$_2$Ge$_{2}$ is known to exhibit antiferromagnetc (AFM) ordering of divalent Eu moments with $T_N$ = 30 K. We have grown EuNi$_2$(P$_{1-x}$Ge$_x$)$_2$ (0.0 $\leq$ $x$ $\leq$ 0.5) single crystals and studied their magnetic, thermodynamic and transport properties. Increasing Ge doping to $x >$ 0.4 results in a well-defined AFM ordered state with $T_N$ = 12 K for $x$ = 0.5. Moreover, the reduced value of magnetic entropy for $x$ = 0.5 at $T_N$ suggests the presence of valance fluctuation/ Kondo effect in this compound. Interestingly, the specific heat exhibits an enhanced Sommerfeld coefficient upon Ge doping. Subsequently, electronic structure calculations lead to a non-integral valence in EuNi$_2$P$_{2}$ but a stable divalent Eu state in EuNi$_2$Ge$_{2}$ which is in good agreement with experimental results.Comment: 7 pages, 8 figure

High-resolution resonant inelastic soft X-ray scattering as a probe of the crystal electrical field in lanthanides demonstrated for the case of CeRh2Si2

The magnetic properties of rare earth compounds are usually well captured by assuming a fully localized f shell and only considering the Hund's rule ground state multiplet split by a crystal electrical field (CEF). Currently, the standard technique for probing CEF excitations in lanthanides is inelastic neutron scattering. Here we show that with the recent leap in energy resolution, resonant inelastic soft X-ray scattering has become a serious alternative for looking at CEF excitations with some distinct advantages compared to INS. As an example we study the CEF scheme in CeRh2Si2, a system that has been intensely studied for more than two decades now but for which no consensus has been reached yet as to its CEF scheme. We used two new features that have only become available very recently in RIXS, high energy resolution of about 30 meV as well as polarization analysis in the scattered beam, to find a unique CEF description for CeRh2Si2. The result agrees well with previous INS and magnetic susceptibility measurements. Due to its strong resonant character, RIXS is applicable to very small samples, presents very high cross sections for all lanthanides, and further benefits from the very weak coupling to phonon excitation. The rapid progress in energy resolution of RIXS spectrometers is making this technique increasingly attractive for the investigation of the CEF scheme in lanthanides

Quantum criticality in the cubic heavy-fermion system CeIn_{3-x}Sn_x

We report a comprehensive study of CeIn$_{3-x}$Sn$_x$ $(0.55 \leq x \leq 0.8)$ single crystals close to the antiferromagnetic (AF) quantum critical point (QCP) at $x_c\approx 0.67$ by means of the low-temperature thermal expansion and Gr\"uneisen parameter. This system represents the first example for a {\it cubic} heavy fermion (HF) in which $T_{\rm N}$ can be suppressed {\it continuously} down to T=0. A characteristic sign change of the Gr\"uneisen parameter between the AF and paramagnetic state indicates the accumulation of entropy close to the QCP. The observed quantum critical behavior is compatible with the predictions of the itinerant theory for three-dimensional critical spinfluctuations. This has important implications for the role of the dimensionality in HF QCPs.Comment: Physical Review Letters, to be publishe

Optical study of archetypical valence-fluctuating Eu-systems

We have investigated the optical conductivity of the prominent valence fluctuating compounds EuIr2Si2 and EuNi2P2 in the infrared energy range to get new insights into the electronic properties of valence fluctuating systems. For both compounds we observe upon cooling the formation of a renormalized Drude response, a partial suppression of the optical conductivity below 100 meV and the appearance of a mid-infrared peak at 0.15 eV for EuIr2Si2 and at 0.13 eV for EuNi2P2. Most remarkably, our results show a strong similarity with the optical spectra reported for many Ce- or Yb-based heavy fermion metals and intermediate valence systems, although the phase diagrams and the temperature dependence of the valence differ strongly between Eu- and Ce-/Yb-systems. This suggests that the hybridization between 4f- and conduction electrons, which is responsible for the properties of Ce- and Yb-systems, plays an important role in valence fluctuating Eu-systems

From financing needs to criminal terrorism: The role of terrorist financing in crime-terror relations

After twenty years of national and international measures to combat financing of terrorism and money laundering, global terrorism has encountered greater restrictions to access the volume of economic resources it needs which has justified its collaboration with criminal organisations or conversion into criminal-terrorist organisations. This study seeks to analyse crime-terror relations by looking at the influence of the fight against terrorist financing in the evolution of global terrorist organisations, which have developed structures to establish a new range of relationships with transnational organised crime with unprecedented intensity. This article highlights some of the features that differentiate global terrorism from other types of terrorism, especially in terms of its objectives, organisational structures and funding possibilities, as well as pointing out a possible effect of the fight against terrorist financing in the relationship between terrorism and crime. Finally, it offers the different contexts where economic, political and social circumstances have created new cooperation models with organised crime groups.Tras veinte años de desarrollo de medidas nacionales e internacionales encaminadas a combatir la financiación del terrorismo y el blanqueo de capitales, el terrorismo global ha encontrado grandes restricciones para acceder al volumen de recursos económicos que necesita. Este estudio aborda la influencia de la lucha contra la financiación del terrorismo en la evolución de las organizaciones terroristas globales y en el cambio de la naturaleza y alcance de las relaciones entre el crimen organizado y el terrorismo. Así mismo examina los diferentes contextos en los que las circunstancias económicas, políticas y sociales han propiciado la creación de nuevos modelos de cooperación de las organizaciones terroristas con los grupos criminales organizados.Ministerio de Ciencia e Innovación del Gobierno de España Ref. PID2020-116646RB-I0