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Measurements of the longitudinal and transverse spin relaxation times of holes in an ensemble of vertically tunnel‐coupled self‐assembled InAs/In0.53$_{0.53}$Al0.24$_{0.24}$Ga0.23$_{0.23}$As quantum dots (QDs), emitting in the telecom spectral range, are reported. The spin coherence is determined using the spin mode‐locking method in the inhomogeneous ensemble of QDs. Modeling the signal allows us to extract the hole spin coherence time to be in the range of T2=0.02−0.4 $T_{2} = 0.02 - 0.4 \textrm{ } \textrm{ } \mu$μs. The longitudinal spin relaxation time T1=0.5 $T_{1} = 0.5 \textrm{ } \textrm{ } \mu$μs is measured using the spin inertia method. The parameters investigated allow us to suggest that the main relaxation mechanism at low magnetic fields is related to the electron–hole spin exchange. [ABSTRACT FROM AUTHOR]

Encapsulated atomic hydrogen in polyhedral oligomeric silsesquioxane (POSS) cages is a promising candidate for spin‐based quantum technologies. Key parameters such as spin relaxation times and magnetic interactions with surrounding electron and nuclear spins can be typically probed with advanced electron paramagnetic resonance (EPR) methods. Here we present a detailed pulsed EPR study of the species H@Si8O12R8 with R=CH3, namely encapsulated atomic hydrogen in the octamethyl POSS derivative. The temperature dependence of the spin‐lattice relaxation rate 1/ T1 ${{T}_{1}}$ is analyzed in terms of a Raman process with a Debye temperature of θD=145 ${{\theta }_{{\rm D}}=145}$ K and a thermally activated process with Ea=794K ${{E}_{a}=794\hskip0.17em\hskip0.17em{\rm K}}$ (552 cm−1), whereas, the phase memory time TM ${T_{\rm{M}} }$ shows the typical shortening behaviour at T<150 ${T \char60 150}$ K observed for all methyl‐containing derivatives. The hyperfine coupling of the cage 29 ${^{29} }$ Si nuclei is measured by hyperfine sublevel correlation (HYSCORE) spectroscopy and is found to fulfil the so‐called “matching condition” at the low‐field EPR transition. The potential of this paramagnetic molecule to perform one‐qubit quantum operations is probed by room‐temperature Rabi oscillations. [ABSTRACT FROM AUTHOR]

In the work described herein, the spin relaxation properties of the mononuclear tetrahedral S=2 [Fe{(SPiPr2)2N}2] complex (1) were studied by employing static and dynamic magnetic measurements at liquid helium temperatures. In the absence of an external direct current (DC) magnetic field, 1 exhibits fast magnetization relaxation. However, in the presence of external magnetic fields of a few kOe, slow relaxation is induced as monitored by alternating current (AC) magnetic susceptibility measurements up to 10 kHz, in the temperature range 2–5 K. Analysis of the temperature dependence of the corresponding relaxation time reveals contributions by Quantum Tunnelling of Magnetization, and the Direct and Orbach processes in the magnetization relaxation mechanism of 1. The energy barrier, Ueff, of the Orbach process, as determined by this analysis, is compared with that related to the zero‐field splitting parameters of 1 which were previously determined by high‐ frequency and ‐field electron paramagnetic resonance and Mössbauer spectroscopies. [ABSTRACT FROM AUTHOR]

Proteins often undergo large-scale conformational transitions, in which secondary and tertiary structure elements (loops, helices, and domains) change their structures or their positions with respect to each other. Simple considerations suggest that such dynamics should be relatively fast, but the functional cycles of many proteins are often relatively slow. Sophisticated experimental methods are starting to tackle this dichotomy and shed light on the contribution of large-scale conformational dynamics to protein function. In this review, we focus on the contribution of single-molecule Förster resonance energy transfer and nuclear magnetic resonance (NMR) spectroscopies to the study of conformational dynamics. We briefly describe the state of the art in each of these techniques and then point out their similarities and differences, as well as the relative strengths and weaknesses of each. Several case studies, in which the connection between fast conformational dynamics and slower function has been demonstrated, are then introduced and discussed. These examples include both enzymes and large protein machines, some of which have been studied by both NMR and fluorescence spectroscopies. [ABSTRACT FROM AUTHOR]

From complex-mixture analysis to in vivo molecular imaging, applications of liquid-state nuclear spin hyperpolarization have expanded widely over recent years. In most cases, hyperpolarized solutions are generated ex situ and transported from the polarization instrument to the measurement device. The sample hyperpolarization usually survives this transport, since the changes in magnetic fields that are external to the sample are typically adiabatic (slow) with respect to the internal nuclear spin dynamics. The passage of polarized samples through weakly magnetic components such as stainless steel syringe needles and ferrules is not always adiabatic, which can lead to near-complete destruction of the magnetization. To avoid this effect becoming “folklore” in the field of hyperpolarized NMR, we present a systematic investigation to highlight the problem and investigate possible solutions. Experiments were carried out on: (i) dissolution-DNP-polarized [1-13C]pyruvate with NMR detection at 1.4T, and (ii) 1.5-T-polarized H2O with NMR detection at 2.5μT. We show that the degree of adiabaticity of solutions passing through metal parts is intrinsically unpredictable, likely depending on many factors such as solution flow rate, degree of remanent ferromagnetism in the metal, and nuclear spin species. However, the magnetization destruction effects can be suppressed by application of an external field on the order of 0.1–10mT.

ABSTRACTGaN-based semiconductors are deemed to be a potential candidate for developing spintronic devices owing to the artificially controllable spin-orbit coupling and the high Curie temperature of GaN-based diluted magnetic semiconductors. Spin injection, spin relaxation dynamics, and spin manipulation are the key issues in the development of GaN-based spintronic devices, which have been reviewed in this article. In the end, a brief section presents the research progress of GaN-based spintronic devices.

Spin relaxation is an important aspect of the spin dynamics of free radicals and can have a significant impact on the outcome of their spin‐selective reactions. Examples range from the use of radicals as spin qubits in quantum information processing to the radical pair reactions in proteins that may allow migratory birds to sense the direction of the Earth's magnetic field. Accurate modeling of spin relaxation, however, is non‐trivial. Bloch–Redfield–Wangsness theory derives a quantum mechanical master equation from system‐bath interactions in the Markovian limit that provides a comprehensive framework for describing spin relaxation. Unfortunately, the construction of the master equation is system‐specific and often resource‐heavy. To address this challenge, we introduce a generalized and efficient implementation of BRW theory as a new feature of the spin dynamics toolkit MolSpin which offers an easy‐to‐use approach for studying systems of reacting radicals of varying complexity. [ABSTRACT FROM AUTHOR]

Molecule‐based magnetic materials are promising candidates for molecular spin qubits, which utilize spin relaxation behavior. Various kinds of transition metal complexes with S=1/2 have been reported to act as spin qubits with long spin‐spin relaxation times (T2). However, the spin qubit properties of low‐spin Ni(III) complexes are not as well known since Ni(III) compounds are often unstable. We report here the slow magnetic relaxation behavior and T2 values for three kinds of low‐spin Ni(III) based complexes with S=1/2 under magnetically diluted conditions. [Ni(cyclam)X2]Y (cyclam=1,4,8,11‐tetraazacyclotetradecane) with octahedral structures and [Ni(mnt)2]− (mnt=maleonitriledithiolate) with a square‐planar structure underwent slow magnetic relaxations in the presence of a dc magnetic bias field. From electron spin resonance (ESR) spectroscopy, the Ni(III) complexes exhibited observable T2, indicating that Ni(III) complexes are promising candidates for use as molecule‐based spin qubits. [ABSTRACT FROM AUTHOR]

We investigate nonequilibrium phenomena in magnetic nano-junctions using a numerical approach that combines classical spin dynamics with the hierarchical equations of motion technique for quantum dynamics of conduction electrons. Our focus lies on the spin dynamics, where we observe non-monotonic behavior in the spin relaxation rates as a function of the coupling strength between the localized spin and conduction electrons. Notably, we identify a distinct maximum at intermediate coupling strength, which we attribute to a competition that involves the increasing influence of the coupling between the classical spin and electrons, as well as the influence of decreasing local density of states at the Fermi level. Furthermore, we demonstrate that the spin dynamics of a large open system can be accurately simulated by a short chain coupled to semi-infinite metallic leads. In the case of a magnetic junction subjected to an external DC voltage, we observe resonant features in the spin relaxation, reflecting the electronic spectrum of the system. The precession of classical spin gives rise to additional side energies in the electronic spectrum, which in turn leads to a broadened range of enhanced damping in the voltage.

Aromatic side chains are important reporters of the plasticity of proteins, and often form important contacts in protein–protein interactions. We studied aromatic residues in the two structurally homologous cross‐β amyloid fibrils HET‐s, and HELLF by employing a specific isotope‐labeling approach and magic‐angle‐spinning NMR. The dynamic behavior of the aromatic residues Phe and Tyr indicates that the hydrophobic amyloid core is rigid, without any sign of "breathing motions" over hundreds of milliseconds at least. Aromatic residues exposed at the fibril surface have a rigid ring axis but undergo ring flips on a variety of time scales from nanoseconds to microseconds. Our approach provides direct insight into hydrophobic‐core motions, enabling a better evaluation of the conformational heterogeneity generated from an NMR structural ensemble of such amyloid cross‐β architecture. [ABSTRACT FROM AUTHOR]

Transcription factors play key roles in orchestrating a plethora of cellular mechanisms and controlling cellular homeostasis. Transcription factors share distinct DNA binding domains, which allows to group them into protein families. Among them, the Forkhead box O (FOXO) family contains transcription factors crucial for cellular homeostasis, longevity and response to stress. The dysregulation of FOXO signaling is linked to drug resistance in cancer therapy or cellular senescence, however, selective drugs targeting FOXOs are limited, thus knowledge about structure and dynamics of FOXO proteins is essential. Here, we provide an extensive study of structure and dynamics of all FOXO family members. We identify residues accounting for different dynamic and structural features. Furthermore, we show that the auto-inhibition of FOXO proteins by their C-terminal trans-activation domain is conserved throughout the family and that these interactions are not only possible intra-, but also inter-molecularly. This indicates a model in which FOXO transcription factors would modulate their activities by interacting mutually.

Time-resolved and time-integrated circularly polarized photoluminescence of excitons and trions in external magnetic fields up to 10 T has been studied in undoped and n-type doped quantum well structures based on ZnSe. In an undoped structure, a circular polarization of photoluminescence induced by magnetic fields corresponded to the Boltzmann distribution of excitons on Zeeman sublevels. The inverse spin orientation of excitons is observed in doped samples with a carrier density of 3 × 1 0 10 cm−2 and higher. Model calculations show that the reason for the inverse spin orientation is the effective depletion of the lowest-exciton Zeeman sublevel as a result of the spin-dependent formation of trions. The trion formation time as a result of exciton-electron binding was determined as 2 ps. This is noticeably shorter than the characteristic time of the exciton-photon interaction. The observed effect can be considered as a way of spin manipulation by electric fields. • The presented work opens a new direction in spintronics, shows the possibility to control the population of exciton Zeeman sublevels by changing the electron density in QWs. • The founded effect is due to the depletion of the lower energy sublevel of the exciton during the trion formation. • The effect can be used to control the exciton's angular momentum using an electric field or additional ultraviolet illumination. • New spin control method and new perspectives for exciton angular momentum control are presented. [ABSTRACT FROM AUTHOR]

NMR studies exploit spin relaxation in a multitude of different ways, providing information on molecular structure and dynamics. Calculating the relaxation rates of NMR active nuclei in multi-spin systems is often a prerequisite for the proper analysis of experimental data. For many researchers the calculations appear complex, often involving different basis sets or expressions describing relaxation in different frames. In this tutorial paper we derive expressions for dipolar relaxation of an I-S two spin spin-system in the presence of a B1 radio frequency field, where spins I and S can be either like or unlike. We consider two different approaches for the derivation of relaxation elements that have been used in the literature, including one where a series of transformations are carried out to the interaction representation of the effective field, comprising B1 and Zeeman components. A second procedure is based on the well-known Solomon equations. We show that both approaches lead to identical results, in the process presenting a pedagogical description of relaxation theory.

A short description of the long-range cooperation of K. Alex Müller and his group with Kazan University in investigations of high-temperature superconductors by the electron paramagnetic resonance (EPR) method is given. Special attention was spared also to personal contacts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Strategy of molecular magnets functionalization inside a ferromagnetic media is proposed. • Residual field of the microparticle arrays affects frequency of magnetic relaxation. • Chemical bond between SMM and the microparticles surface changes relaxation frequency. • Color of magnetic noise depends on physical origin of magnetic relaxation. • Chemically designed spin interface is convenient for spintronics and quantum computing. Interaction between single molecule magnets (SMMs) and metal surface is a hot topic promising controllable deposition of SMMs, programmable frequency of magnetic relaxation and addressed reading of information. In this paper, we develop strategy of the Er3+ based SMM functionalization by its penetration inside the arrays of Ferromagnetic Micro Particles (FMPs). We show that predictable residual magnetic field of the FMPs arrays is an effective tool for regulation of the frequency maximum of imaginary magnetic susceptibility. We analyzed color of magnetic noise in respect to physical origin of magnetic relaxation. An additional channel for control over spin noise is formation of chemical bonds between SMM and the FMPs surface. Oxidation of an Er complex transforms 20 ± 5 % of the initial 10-coordinated SMM complex to the 9-coordinated complex with reduced relaxation time. Memorized residual magnetization of the composite material allows one to set desirable relaxation frequency in the individual micronized cells to create a sound frequency register. The proposed compaction of SMMs of different types in ferromagnetic composites provides engineering of the chemically designed spin interface on ferromagnetic surface for spintronics and quantum computing. [ABSTRACT FROM AUTHOR]

The electrical control of a spin qubit in a quantum dot (QD) relies on spinâ€"orbit coupling (SOC), which could be either intrinsic to the underlying crystal lattice or heterostructure, or extrinsic via, for example, a micro-magnet. In experiments, micromagnets have been used as a synthetic SOC to enable strong coupling of a spin qubit in quantum dots with electric fields. Here we study theoretically the spin relaxation, pure dephasing, spin manipulation, and spinâ€"photon coupling of an electron in a QD due to the synthetic SOC induced spinâ€"orbit mixing. We find qualitative difference in the spin dynamics in the presence of a synthetic SOC compared with the case of the intrinsic SOC. Specifically, spin relaxation due to the synthetic SOC and deformation potential phonon emission (or Johnson noise) shows B 0 5 (or B 0) dependence with the magnetic field, which is in contrast with the B 0 7 (or B 0 3 ) dependence in the case of the intrinsic SOC. Moreover, charge noise induces fast spin dephasing to the first order of the synthetic SOC, which is in sharp contrast with the negligible spin pure dephasing in the case of the intrinsic SOC. These qualitative differences are attributed to the broken time-reversal symmetry (T -symmetry) of the synthetic SOC. An SOC with broken T -symmetry (such as the synthetic SOC from a micro-magnet) eliminates the ‘Van Vleck cancellation’ and causes a finite longitudinal spinâ€"electric coupling that allows the longitudinal coupling between spin and electric field, and in turn allows spin pure dephasing. Finally, through proper choice of magnetic field orientation, the electric-dipole spin resonance via the synthetic SOC can be improved with potential applications in spin-based quantum computing. [ABSTRACT FROM AUTHOR]

A heteroatomic analog of 1,1,2,3,3-pentamethylenepropane, the diradical N-[bis(4,4,5,5-tetramethyl-3-oxide-1-oxyl-4,5-dihydro-1H-imidazol-2-yl)methylene]-2-methylpropane-2-amine oxide (1) with two C(sp2)-bonded nitronyl nitroxide fragments in magnetically concentrated (single crystal) and magnetically diluted (frozen solution) forms was studied by EPR spectroscopy. The longitudinal and transverse relaxation times of diradical 1 in the frozen solution were measured for the first time; a significant difference in the intramolecular exchange interaction was demonstrated for the cases of the single crystal and the frozen solution. The influence of solvation on the value of the intramolecular exchange interaction in this class of compounds was discussed. [ABSTRACT FROM AUTHOR]

The unexpected formation of a highly strained polycyclic amine was observed in a one-pot synthesis from cyclopentanone, dimethyl fumarate and ammonium acetate. This multistep reaction includes 1,3-dipolar cycloaddition of dimethyl fumarate to the cyclic azomethine ylide formed in situ from cyclopentanone and ammonia. The polycyclic amine product was easily converted into a sterically shielded polycyclic nitroxide. The EPR spectra and spin relaxation behavior of the nitroxide were studied in solution. The spin relaxation seems well suited for the use as a biological spin label and are comparable with those of cyclic nitroxides with two spirocyclic moieties adjacent to the N–O· group.

This study explores the impact of thermal motion on the magnetic compass mechanism in migratory birds, focusing on the radical pair mechanism within cryptochrome photoreceptors. The coherence of radical pairs, crucial for magnetic field inference, is curbed by spin relaxation induced by intra-protein motion. Molecular dynamics simulations, density-functional-theory-based calculations, and spin dynamics calculations were employed, utilizing Bloch-Redfield-Wangsness (BRW) relaxation theory, to investigate compass sensitivity. Previous research hypothesized that European robin's cryptochrome 4a (ErCry4a) optimized intra-protein motion to minimize spin relaxation, enhancing magnetic sensing compared to the plant Arabidopsis thaliana's cryptochrome 1 (AtCry1). Different correlation times of the nuclear hyperfine coupling constants in AtCry1 and ErCry4a were indeed found, leading to distinct radical pair recombination yields in the two species, with ErCry4a showing optimized sensitivity. However, this optimization is likely negligible in realistic spin systems with numerous nuclear spins. Beyond insights in magnetic sensing, the study presents a detailed method employing molecular dynamics simulations to assess for spin relaxation effects on chemical reactions with realistically modelled protein motion, relevant for studying radical pair reactions at finite temperature., (© 2024 The Authors. ChemPhysChem published by Wiley-VCH GmbH.)

Spin‐related phenomena in optoelectronic materials can revolutionize several technological applications in the areas of data processing and storage, quantum computing, lighting, energy harvesting, sensing, and healthcare. A fundamental boost to this promising field can be envisaged thanks to the use of two emerging materials, which have recently been receiving increasing scientific attention: organic semiconductors (OSCs) and halide perovskites (HPs). Here, the first progress in the resulting fields, organic‐ and perovskite‐based spintronics, is reviewed, which will enable the manipulation of spin, charges, and photons in spin/optoelectronic devices. A link between these two classes of materials is created by highlighting the pros and cons of each technology, and their potential applications in new multifunctional spintronic devices are discussed. Current challenges in the field are also outlined, and convenient approaches to overcome them are proposed. [ABSTRACT FROM AUTHOR]

The paper presents the results of an EPR study of a new organic photovoltaic composite with a nonfullerene acceptor PBDB-T : IT-M. The parameters of the EPR spectra of all photogenerated spin charge carriers, both trapped and mobile, have been determined, which are in good agreement with previously reported data. The dependences of the spin concentration of all trapped and mobile charge carriers on the photon energy demonstrate an extreme increase in the region of 2.37 eV, which coincides with the band gap of the PBDB-T : IT-M polymer composite. The introduction of 2,5-diphenyloxazole (PPO) as a photoactivator into the system of trace additives improves the composite morphology as a result of more intense π–π interaction between the components, which enhances the exchange interaction between them and stabilizes the amount of spin charge carriers, mainly localized in the energy traps of the polymer matrix. The exchange interaction between polymers and diphenyloxazole in the composite leads to a twofold increase in the number of spins in the energy region close to the band gap of the composite. [ABSTRACT FROM AUTHOR]

We explain how to conduct a pseudo-3D relaxation series NUS measurement so that it can be reconstructed by existing 3D NUS reconstruction methods to give accurate relaxation values. We demonstrate using reconstruction algorithms IST and SMILE that this 3D approach allows lower sampling densities than for independent 2D reconstructions. This is in keeping with the common finding that higher dimensionality increases signal sparsity, enabling lower sampling density. The approach treats the relaxation series as ordinary 3D time-domain data whose imaginary part in the pseudo-dimension is zero, and applies any suitably linear 3D NUS reconstruction method accordingly. Best results on measured and simulated data were achieved using acquisitions with 9 to 12 planes and exponential spacing in the pseudo-dimension out to ~ 2 times the inverse decay time. Given these criteria, in typical cases where 2D reconstructions require 50% sampling, the new 3D approach generates spectra reliably at sampling densities of 25%. [ABSTRACT FROM AUTHOR]

Colloidal diluted magnetic semiconductor (DMS) nanocrystals are model systems for studying spin effects in semiconductor nanostructures with relevance to future spin-based information processing technologies. The introduction of excess delocalized charge carriers into such nanocrystals turns on strong dopant-carrier magnetic exchange interactions, with important consequences for the physical properties of these materials. Here, we use pulsed electron paramagnetic resonance (pEPR) spectroscopy to probe the effects of excess conduction band electrons on the spin dynamics of colloidal Mn(2+)-doped ZnO nanocrystals. Mn(2+) spin-lattice relaxation is strongly accelerated by the addition of even one conduction band electron per Zn1-xMnxO nanocrystal, attributable to the introduction of a new exchange-based Mn(2+) spin relaxation pathway. A kinetic model is used to describe the enhanced relaxation rates, yielding new insights into the spin dynamics and electronic structures of these materials with potential ramifications for future applications of DMS nanostructures in spin-based technologies.

Colloidal diluted magnetic semiconductor (DMS) nanocrystals are model systems for studying spin effects in semiconductor nanostructures with relevance to future spin-based information processing technologies. The introduction of excess delocalized charge carriers into such nanocrystals turns on strong dopant-carrier magnetic exchange interactions, with important consequences for the physical properties of these materials. Here, we use pulsed electron paramagnetic resonance (pEPR) spectroscopy to probe the effects of excess conduction band electrons on the spin dynamics of colloidal Mn(2+)-doped ZnO nanocrystals. Mn(2+) spin-lattice relaxation is strongly accelerated by the addition of even one conduction band electron per Zn1-xMnxO nanocrystal, attributable to the introduction of a new exchange-based Mn(2+) spin relaxation pathway. A kinetic model is used to describe the enhanced relaxation rates, yielding new insights into the spin dynamics and electronic structures of these materials with potential ramifications for future applications of DMS nanostructures in spin-based technologies.

The prevalent view on whether Ras is druggable has gradually changed in the recent decade with the discovery of effective inhibitors binding to cryptic sites unseen in the native structures. Despite the promising advances, therapeutics development toward higher potency and specificity is challenged by the elusive nature of these binding pockets. Here we derive a conformational ensemble of guanosine diphosphate (GDP)-bound inactive Ras by integrating spin relaxation-validated atomistic simulation with NMR chemical shifts and residual dipolar couplings, which provides a quantitative delineation of the intrinsic dynamics up to the microsecond timescale. The experimentally informed ensemble unequivocally demonstrates the preformation of both surface-exposed and buried cryptic sites in Ras·GDP, advocating design of inhibition by targeting the transient druggable conformers that are invisible to conventional experimental methods. The viability of the ensemble-based rational design has been established by retrospective testing of the ability of the Ras·GDP ensemble to identify known ligands from decoys in virtual screening. [ABSTRACT FROM AUTHOR]

The entropy change during spin relaxation for a realistic model system is studied, whose spin dynamics can be handled with the Boltzmann equation. The time evolution of the von Neumann entropy is monitored during the process and is compared with the recently introduced concept of the Loschmidt echo envelope. The time evolution of the two quantities is remarkably similar which helps to distinguish reversible and irreversible changes to the ensemble spin state. The method is also demonstrated for a toy model of nuclear magnetic resonance, where the usual π spin echo is performed numerically, and the echo envelope also follows the time evolution of the von Neumann entropy. The numerical approach highlights the utility of the entropy concept in analyzing various processes which occur during spin relaxation. [ABSTRACT FROM AUTHOR]

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MEMS vapor cells with buffer gas are the core components of chip scale atomic sensors due to the spin precession. We microfabricated rubidium vapor cells filled with neon based on MEMS technology and characterized the performance of MEMS vapor cells by measuring the longitudinal relaxation time. The dependence of spin relaxation time on buffer gas pressure and cell temperature was theoretically and experimentally investigated and the consistency was achieved. This provides a potential simpler approach to evaluate the performance of chip scale atomic sensors, such as atomic magnetometers, based on MEMS vapor cells. [ABSTRACT FROM AUTHOR]

The paper presents the results of an EPR study of the magnetic, relaxation, and dynamic parameters of spin charge carriers photogenerated by light in photovoltaic polymer composites, based on poly(3-dodecylthiophene) (P3DDT) and 6,6-phenyl-C61-butyric acid methyl ester (PCBM), in the presence of coumarin admixed to the system. It has been shown that the concentration of polarons and fullerene radical anions is characterized by a nonmonotonic dependence on the energy of incident photons with extrema at 1.9 and 2.7 eV. The largest increase in the concentration of mobile charge carriers was observed in composites with a coumarin content of 3 or 6 wt %. A significant slowdown of the carrier recombination process in the composites containing 3–6 wt % coumarin was observed after switching off the light. The temperature dependences of the concentrations of mobile and localized charge carriers for P3DDT/PCBM samples with a coumarin content of 3 wt % showed enhancement of the exchange interaction between charge carriers. The data obtained lead to the conclusion that coumarin affects spin interactions in the polymer composite. [ABSTRACT FROM AUTHOR]

A system of coupled kinetic equations for the electron density and spin density distribution functions has been obtained based on the quantum kinetic equation. The collision integrals in the kinetic equations are written for an arbitrary scattering potential, taking into account the spin-orbit interaction of conduction electrons with scattering defects. As applied to the spin system of conduction electrons, the idea of a "reduced" description of transport phenomena is developed. The description of the system in terms of distribution functions depending on the quasi-momentum of electrons reduces to a description in terms of macroscopic mean quantities: electron density, spin density, electron flux, and spin current. [ABSTRACT FROM AUTHOR]

The conformational landscape of multi-domain proteins is inherently linked to their specific functions. This also holds for polyubiquitin chains that are assembled by two or more ubiquitin domains connected by a flexible linker thus showing a large interdomain mobility. However, molecular recognition and signal transduction are associated with particular conformational substates that are populated in solution. Here, we apply high-resolution NMR spectroscopy in combination with dual-scale MD simulations to explore the conformational space of K6-, K29-, and K33-linked diubiquitin molecules. The conformational ensembles are evaluated utilizing a paramagnetic cosolute reporting on solvent exposure plus a set of complementary NMR parameters. This approach unravels a conformational heterogeneity of diubiquitins and explains the diversity of structural models that have been determined for K6-, K29-, and K33-linked diubiquitins in free and ligand-bound states so far. We propose a general application of the approach developed here to demystify multi-domain proteins occurring in nature. [Display omitted] • General workflow for studying multi-domain proteins at atomic resolution • Heterogeneous conformational character of K6-, K29-, and K33-linked ubiquitin dimers • Integrative approach combines chemical biology, NMR spectroscopy, and MD simulations • Structural basis for the observed diversity of ubiquitin dimer crystal structures Schneider et al. investigated the conformational landscape of various ubiquitin dimers by applying an integrative approach. The ubiquitin dimers probed in their study show a pronounced conformational heterogeneity. Besides ubiquitin dimers, the here designed workflow will make it possible to study the conformational space of multi-domain proteins in general. [ABSTRACT FROM AUTHOR]

Antisite disorders play a critical role in determining the magnetic ground state of the La 2 NiMnO 6 double perovskite compounds that show multifunctional behaviours and spin-glass phases at lower temperatures. The spin-glass (SG) state and magnetization relaxation in these compounds have been studied extensively; however, the polydispersity of the SG state remains elusive. Employing ac-magnetic susceptibility χ (ω , T) and temperature-dependent electron spin resonance (ESR) spectroscopy, herein, we probe the polydispersity of the SG phase in La 2 NiMnO 6 crystallites. We employed X-ray photoelectron spectroscopy (XPS) to -investigate the crystallite size-dependent variable fractions of Mn3+/Mn4+ (Ni2+/Ni3+) cations and their influence on completing exchange interactions. Mn- 2p core-level XPS spectra suggest a dominant Mn4+ + Ni2+→Mn3+ + Ni3+ charge transfer peak that appeared as a satellite peak at lower binding energy than the Mn core-level. The observed differences in saturation magnetization (M S) as a function of crystallite size indicate the variation in the degree of antisites disorder. Competing magnetic interactions driven by mixed valence and disorder facilitate a spin-glass (SG) phase at lower temperatures. Utilizing ESR measurement across paramagnetic → competing ferro/antiferromagnetic phase, a modified g -factor that ranges from 2.050-2.037 is observed in the paramagnetic region. The line width of the ESR signals is found to be increased across the transition suggesting spin-freezing characteristics. Cole-Cole plots obtained from χ (ω , T) data indicate collective spin relaxation dynamics in the proximity of the freezing temperature. Our findings suggest the importance of the size effect and its relation with the degree of antisites disorders in these crystallites. These experimental results enable the La 2 NiMnO 6 compound to find its possible applications in new areas of material research. • The distinct valence states of Mn (Ni) cations. • Multiple magnetic transitions. • Spin-glass phases in La 2 NiMnO 6 double perovskites. • Antisite-disorder driven spin-glass phase. • Polydispersity of spin glass phase. [ABSTRACT FROM AUTHOR]

We have systematically investigated the structural properties, carrier lifetimes, namely, photoluminescence (PL) lifetimes (τPL), and electron spin relaxation times (τs) in (110) GaAs/AlGaAs multiple quantum wells (MQWs) by using time-resolved PL measurements. The MQWs were grown by molecular beam epitaxy within a wide range of the growth temperature Tg (430–600 °C) and a high V/III flux ratio using As2. At 530 °C < Tg < 580 °C, we found that the quality of the heterointerfaces is significantly improved, resulting in τPL~40 ns at RT, one order of magnitude longer than those reported so far. Long τs (~6 ns) is also observed at RT.