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Multicharged Phthalocyanines as Selective Ligands for G-Quadruplex DNA Structures
摘要： The stabilization of G-Quadruplex DNA structures by ligands is a promising strategy for telomerase inhibition in cancer therapy since this enzyme is responsible for the unlimited proliferation of cancer cells. To assess the potential of a compound as a telomerase inhibitor, selectivity for quadruplex over duplex DNA is a fundamental attribute, as the drug must be able to recognize quadruplex DNA in the presence of a large amount of duplex DNA, in the cellular nucleus. By using different spectroscopic techniques, such as ultraviolet-visible, fluorescence and circular dichroism, this work evaluates the potential of a series of multicharged phthalocyanines, bearing four or eight positive charges, as G-Quadruplex stabilizing ligands. This work led us to conclude that the existence of a balance between the number and position of the positive charges in the phthalocyanine structure is a fundamental attribute for its selectivity for G-Quadruplex structures over duplex DNA structures. Two of the studied phthalocyanines, one with four peripheral positive charges (ZnPc1) and the other with less exposed eight positive charges (ZnPc4) showed high selectivity and affinity for G-Quadruplex over duplex DNA structures and were able to accumulate in the nucleus of UM-UC-3 bladder cancer cells.
关键词： telomerase inhibition,selectivity,salmon sperm DNA,UV-Vis,circular dichroism,hyperchromism,G-Quadruplexes,G4-FID,multicharged phthalocyanines
更新于2025-11-21 11:08:12
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Generalized perspective on chiral measurements without magnetic interactions
摘要： We present a unified description of several methods of chiral discrimination based exclusively on electric-dipole interactions. It includes photoelectron circular dichroism (PECD), enantiosensitive microwave spectroscopy (EMWS), photoexcitation circular dichroism (PXCD), and photoelectron-photoexcitation circular dichroism (PXECD). We show that, in spite of the fact that the physics underlying the appearance of a chiral response is very different in all these methods, the enantiosensitive and dichroic observable in all cases has a unique form. It is a polar vector given by the product of (i) a molecular pseudoscalar and (ii) a field pseudovector specified by the configuration of the electric fields interacting with the isotropic ensemble of chiral molecules. The molecular pseudoscalar is a rotationally invariant property, which is composed from different molecule-specific vectors and in the simplest case is a triple product of such vectors. The key property that enables the chiral response is the noncoplanarity of the vectors forming such triple product. The key property that enables chiral detection without relying on the chirality of the electromagnetic fields is the vectorial nature of the enantiosensitive observable. Our compact and general expression for this observable shows what ultimately determines the efficiency of the chiral signal and if, or when, it can reach 100%. We also discuss the differences between the two phenomena, which rely on the bound states, PXCD and EMWS, and the two phenomena using the continuum states, PECD and PXECD. Finally, we extend these methods to arbitrary polarizations of the electric fields used to induce and probe the chiral response.
关键词： photoelectron-photoexcitation circular dichroism,electric-dipole interactions,field pseudovector,enantiosensitive microwave spectroscopy,photoexcitation circular dichroism,molecular pseudoscalar,chiral discrimination,photoelectron circular dichroism
更新于2025-09-23 15:23:52
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Correlation between magneto-optical and transport properties of Sr doped manganite films
摘要： The features of electronic structure of La0.7Sr0.3MnO3, Pr0.8Sr0.2MnO3, and Pr0.6Sr0.4MnO3 polycrystalline films of different thickness have been investigated using magnetic circular dichroism (MCD) in the range of 1.1e4.2 eV. The temperature behavior of the samples electrical resistance were also has been studied. It was found that films with high Sr content (0.3 and 0.4) act as high-temperature semiconductors, while the maximum in the temperature dependences of resistivity these films indicates the transition of the samples to the metallic state at some temperature TM-S, which is different for different sample thickness. The films with the lower Sr content (0.2) act as insulators in the used temperature range. The MCD spectra have been decomposed to the Gaussian-shaped lines, and the temperature dependence of intensity of each line has been analyzed in comparison with temperature dependence of the films magnetization and with their electric conductivity type. Different temperature behavior of the intensity of four specified Gaussian-lines was revealed for semiconductor films. In the case of insulating Pr0.8Sr0.2MnO3 samples, the intensity of three specified Gaussian lines changes with the temperature in the same way as the magnetization changed. It was established that the lanthanide (La, Pr) type does not affect the MCD spectra shape for the films with the same electrical conductivity type. Besides, the correlation between the MCD data of the films and their conductivity type was revealed. Due to the detailed analysis of the specified Gaussian lines with taking into account the well-known in the literature absorption bands, lying outside the studied spectral region, the MCD bands for the studied manganite films have been identified with electronic transitions of a different nature.
关键词： Magnetic circular dichroism,Thin films,Electronic properties,Electrical transport,Crystal structure,Manganites
更新于2025-09-23 15:23:52
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Current-induced domain wall oscillations in a nanowire imaged by time-resolved photoemission electron microscopy
摘要： We study reversible domain wall motion in half-ring Ni80Fe20 nanowires on a nanosecond (ns) timescale in a truly current-induced pump-probe experiment using an energy filtered, aberration-corrected photoemission electron microscope. The x-ray magnetic circular dichroism signal is probed at different time delays before, during and after the current pulse in a stroboscopic mode with circularly polarized synchrotron radiation in the energy range of the Fe L3-edge (707 eV). We observe lateral domain wall oscillations with a frequency of ～ 0.4 GHz. Comparing the results to a proposed string model, we find that the domain wall oscillations can be described as string-like asymmetric oscillations.
关键词： Synchrotron radiation,Photoemission electron microscopy,X-ray magnetic circular dichroism,Pump-probe mode
更新于2025-09-23 15:23:52
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Chiroptical Properties of Twisted Acenes: Experimental and Computational Study
摘要： Acenes that are twisted out of planarity are expected to display chiroptical properties. However, the effect of twisting on the chiroptical properties of acenes was never investigated computationally or experimentally. Here, we present a computational investigation of twisted anthracene to pentacenes, combined with an experimental study using a series of helically locked acenes, twisted to different torsional angles in their enantiopure form. The lowest energy transition, which is relatively weak in acenes, becomes dominant in their circular dichroism spectra upon twisting. We find that the rotational strength of acenes consistently increases with increasing twist. The experimental data obtained from enantiopure tethered twistacenes show the same trend as the calculated result, with a strong Cotton effect and anisotropy factor, rendering twisted acenes excellent chiroptical materials.
关键词： cyclophanes,twistacenes,acenes,chiroptical properties,circular dichroism
更新于2025-09-23 15:23:52
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Chiral Recognition of L- and D- Amino Acid by Porphyrin Supramolecular Aggregates
摘要： We report of the interactions between four amino acids lysine (Lys), arginine (Arg), histidine (His), and phenylalanine (Phe) with the J-aggregates of the protonated 5,10,15,20-tetrakis(4-sulfonatophenyl)-porphyrin H4TPPS. Several aspects of these self-assembled systems have been analyzed: (i) the chiral transfer process; (ii) the hierarchical effects leading to the aggregates formation; and, (iii) the influence of the amino acid concentrations on both transferring and storing chiral information. We have demonstrated that the efficient control on the J-aggregates chirality is obtained when all amino acids are tested and that the chirality transfer process is under hierarchical control. Finally, the chiral porphyrin aggregates obtained exhibit strong chiral inertia.
关键词： porphyrin,self-assembly,amino acid,circular dichroism,supramolecular chirality
更新于2025-09-23 15:22:29
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Chiral semiconductor nanorod heterostructures with high photocatalysis activity
摘要： Chiral semiconductor nanorods and their heterostructures have attracted intense attention. In this work, it was shown that chiral amino acids on CdSe@CdS semiconductor nanorods (SNR) displayed circular dichroism bands (CD, 200–480 nm). Longer SNRs were found to induce stronger CD intensities, while an increase in the SNR diameter led to a clear CD band redshift. Multi-site post-growth of platinum (Pt) and gold (Au) further enhanced the CD intensity and induced CD band transitions. Electromagnetic calculations revealed that the metal post-growth gave rise to a strong electromagnetic field enhancement, with Pt inducing a stronger enhancement than Au. The optimized chiral multi-sites platinum on SNR displayed higher photocatalytic activities manifested that the deposited metal endowed energy transfer and enhanced the separation of photo-excited electrons and holes. These findings demonstrated that the multi-sites deposited metal provided a method to produce strong optical activity of nanostructures by adjusting the morphology of the semiconductor nanorod.
关键词： circular dichroism,metal growth,heterostructure,semiconductor nanorods
更新于2025-09-23 15:22:29
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The Consequences of Adding a Twist to Acenes
摘要： The Consequences of Adding a Twist to Acenes. Significance: Acenes are a unique class of polycyclic aromatic hydrocarbons often employed in organic electronics. The parent acenes are planar, but they are readily twisted out of planarity upon substitution. It was previously assumed that twisting may affect the optical and electronic properties of acenes. However, the effect of twisting could not be directly studied because the substituents were also involved in inducing different twisting angles. Here, Gidron and co-workers synthesize a series of tethered acenes with a twist of various angles to embark on studies on the effect of the twist on their properties. Comment: Ant-Cn were conformationally as well as photochemically stable. X-ray crystal structures of the Ant-Cn series showed that the twisting angle of the anthracene varied from 23° to 38°. Photophysical measurements suggest that, upon twisting, the p-band absorption increases in intensity, as well as showing a bathochromic shift. In addition, the fluorescence quantum efficiency and the rate of radiative decay decreases, while the rate of nonradiative decay increases. Interestingly, the isolated M and P enantiomers of Ant-C5 showed an anisotropy factor (g factor) of 2 × 10–2, which is higher than those measured for [6]helicene and [5]helicene (4–9 × 10–3).
关键词： fluorescence,polycyclic aromatic hydrocarbons,acenes,circular dichroism
更新于2025-09-23 15:22:29
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-shaped chiral metamaterials
摘要： A highly sensitive refractive index sensor based on the conjugated bilayer-shaped chiral metamaterial is proposed. It is composed of two-shaped structures and a microstrip connecting line. The strong conductive coupling between two-shaped structures can be realized by microstrip connecting line. The chiral metamaterial shows giant circular dichroism (CD) effect, and the CD effect can up to 93.8% and 96.2% at 1.767Thz and 3.008Thz, respectively. The physical origin of the observed CD effect is elucidated through distributions of magnetic and current at resonances. The designed conjugated bilayer-shaped chiral metamaterial as a refractive index sensor can achieve sensitivity of 1.065Thz/RIU and 1.777Thz/RIU, respectively. The effect of structural parameter on the sensitivity and CD spectra is investigated. Through this study we presented the giant CD metamaterial based on conductive coupling and its application potentials for low detection-limit physical and biochemical sensing applications.
关键词： chiral metamaterial,conductive coupling,circular dichroism,resonance,refractive index sensor,metamaterial
更新于2025-09-23 15:22:29
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<i>l</i> -Stercobilin-HCl and <i>d</i> -Urobilin-HCl. Analysis of Their Chiroptical and Conformational Properties by VCD, ECD, CPL Experiments and MD, DFT Calculations
摘要： Vibrational circular dichroism (VCD) and IR spectra of dichloromethane solutions of l-stercobilin and d-urobilin hydrochlorides have been recorded in the mid-IR region. The spectra are best interpreted by combining molecular dynamics (MD) calculations and DFT calculations within the QM/MM ONIOM-type framework, and the combined predicted results are better and more informative than the more standard analysis provided by DFT calculations. The same approach also sheds light on the Cotton effect sign inversion of room temperature versus low temperature electronic CD (ECD) spectra of the same compounds in methanol-glycerol solution. Finally, circularly polarized luminescence (CPL) spectra for l-stercobilin in chloroform solution provide information on the excited state geometry of this molecule.
关键词： Vibrational circular dichroism,electronic CD,molecular dynamics,IR spectra,QM/MM ONIOM-type framework,Cotton effect,circularly polarized luminescence,DFT calculations
更新于2025-09-23 15:21:21