Magnetic Resonance Experiments Research Articles

Diffusion and structure of propylene carbonate-metal salt electrolyte solutions for post-lithium-ion batteries: From experiment to simulation.

The diffusion of cations in organic solvent solutions is important for the performance of metal-ion batteries. In this article, pulsed field gradient nuclear magnetic resonance experiments and fully atomistic molecular dynamic simulations were employed to study the temperature-dependent diffusive behavior of various liquid electrolytes representing 1M propylene carbonate solutions of metal salts with bis(trifluoromethylsulfonyl)imide (TFSI-) or hexafluorophosphate (PF6-) anions commonly used in lithium-ion batteries and beyond. The experimental studies revealed the temperature dependence of the diffusion coefficients for the propylene carbonate (PC) solvent and for the anions following an Arrhenius type of behavior. It was observed that the PC molecules are the faster species. For the monovalent cations (Li+, Na+, K+), the PC solvent diffusion was enhanced as the cation size increased, while for the divalent cations (Mg2+, Ca2+, Sr2+, Ba2+), the opposite trend was observed, i.e., the diffusion coefficients decreased as the cation size increased. The anion diffusion in LiTFSI and NaTFSI solutions was found to be similar, while in electrolytes with divalent cations, a decrease in anion diffusion with increasing cation size was observed. It was shown that non-polarizable charge-scaled force fields could correspond perfectly to the experimental values of the anion and PC solvent diffusion coefficients in salt solutions of both monovalent (Li+, Na+, K+) and divalent (Mg2+, Ca2+, Sr2+, Ba2+) cations at a range of operational temperatures. Finally, after calculating the radial distribution functions between cations, anions, and solvent molecules, the increase in the PC diffusion coefficient established with the increase in cation size for monovalent cations was clearly explained by the large hydration shell of small Li+ cations, due to their strong interaction with the PC solvent. In solutions with larger monovalent cations, such as Na+, and with a smaller solvation shell of PC, the PC diffusion is faster due to more liberated solvent molecules. In the salt solutions with divalent cations, both the anion and the PC diffusion coefficients decreased as the cation size increased due to an enhanced cation-anion coordination, which was accompanied by an increase in the amount of PC in the cation solvation shell due to the presence of anions.

Purification of Potential Antimicrobial Metabolites from Endophytic Fusarium oxysporum Isolated from Myrtus communis.

The rise of microbial resistance and emerging infections pose significant health threats. Natural products from endophytic fungi offer a promising source of novel compounds with the potential as major drug leads. This research aims to screen Myrtus communis and Moringa oleifera for endophytic fungi and screen their metabolites for antibacterial and antifungal potential. Six endophytic fungal strains were isolated using a potato dextrose agar (PDA) medium. The M. communis isolates were designated MC1, MC2, and MC3, and the M. oleifera isolates were named MO1, MO2, and MO3. Preliminary bioactivity testing revealed that the MC3 isolate exhibited significant growth inhibition against multidrug-resistant bacterial and fungal pathogens, including Staphylococcus aureus, Enterococcus faecalis, Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coli, Candida albicans, and Candida glabrata. The MC3 isolate was identified as Fusarium oxysporum through morphological and microscopic methods. For metabolite production, the fungal strain was cultured in potato dextrose broth (PDB) medium at 28°C for 14days in a shaking incubator. The metabolites were purified using various chromatographic techniques, HPLC and GC-MS. The GC-MS analysis of the bioactive compound containing fungal strain (F. oxysporum) revealed multiple compounds at different retention times using the NIST-20 Library. Based on RSI values and probability indices, two compounds were targeted for further purification. Structure elucidation was performed using 1D and 2D nuclear magnetic resonance (NMR) experiments on a Varian 500 NMR machine. The compounds identified were ethyl iso-allocholate (C26H44O5, exact mass 436.32) and 1-monolinoleoyl glycerol trimethylsilyl ether (C27H56O4Si2, exact mass 500.37). The MS (NIST-20) library facilitated the investigation of the in silico antimicrobial activity of these compounds against the elastase virulence protein of P. aeruginosa and protease Sapp1p from C. parapsilosis. Both the compounds were docked with druggable proteins using the Glide induced fit docking (IFD) algorithm. The ethyl iso-allocholate and 1-monolinoleoyl glycerol trimethylsilyl ether compounds showed binding scores - 10.07kcalmol-1 and - 7.47kcalmol-1 against elastase, and - 8.16kcalmol-1 and - 6.89kcalmol-1 against aspartic protease, respectively. In vitro studies confirmed the inhibitory activity of these compounds against multidrug-resistant P. aeruginosa and E. faecalis. Ethyl iso-allocholate exhibited higher bioactivity against P. aeruginosa with inhibition rates of 41%, 27%, and 35% at concentrations of 1000, 500, and 250µgmL-1, respectively. These results suggest that bioactive compounds from F. oxysporum have the potential as antimicrobial agents, warranting further research.

Sub-Nanometer-Range Structural Effects From Mg2+ Incorporation in Na-Based Borosilicate Glasses Revealed by Heteronuclear NMR and MD Simulations.

Magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) experiments and molecular dynamics (MD) simulations were employed to investigate Na2O-B2O3-SiO2 and MgO-Na2O-B2O3-SiO2 glass structures up to ≈0.3 nm. This encompassed the {Na[p]}, {Mg[p]}, and {B[3], B[4]} speciations and the {Si, B[p], M[p]}-BO and {Si, B[p], M[p]}-NBO interatomic distances to the bridging oxygen (BO) and nonbridging oxygen (NBO) species, where the superscript indicates the coordination number. The MD simulations revealed the dominance of Mg[5] coordinations, as mirrored in average Mg2+ coordination numbers in the 5.2-5.5 range, which are slightly lower than those of the larger Na+ cation but with a narrower coordination distribution stemming from the higher cation field strength (CFS) of the smaller divalent Mg2+ ion. We particularly aimed to elucidate such Na+/Mg2+ CFS effects, which primarily govern the short-range structure but also the borosilicate (BS) glass network order, where both MD simulations and heteronuclear double-resonance 11B/29Si NMR experiments revealed a reduction of B[4]-O-Si linkages relative to B[3]-O-Si upon Mg2+-for-Na+ substitution. These effects were quantified and discussed in relation to previous literature on BS glasses, encompassing the implications for simplified structural models and descriptions thereof.

Evidence for NMR Relaxation Enhancement in a Protic Ionic Liquid by the Movement of Protons Independent of the Translational Diffusion of Cations.

The molecular dynamics, thermal stability, and ionic conductivity were studied in the protic ionic liquid 1-methylimidazolium bis(trifluoromethylsulfonyl)imide ([MIm][TFSI]). The relaxation of the 1H spin-lattice of cations in the measured frequency range (10 kHz to 20 MHz) and temperature (298 to 343 K) is sensitive mainly to slow processes occurring in the molecular dynamics of protic ionic liquid and dominated by the contribution of intermolecular translational diffusion. Molecular rotations give only a constant contribution and become significant in the higher frequency range. An interesting feature is the observed enhancement of the 1H spin-lattice relaxation below 0.03 MHz attributed to the exchange of protons (order of 10-5 s) between imidazolium cations. The measurements of the self-diffusion coefficient of hydrogen atoms of cation from 298 to 343 K additionally confirm the observed phenomenon. The coefficient for exchangeable protons -NH is higher than for the cation. The nuclear magnetic resonance (NMR) experiments provide unambiguous evidence for proton transport decoupled from molecular diffusion of ions and support the conclusion that the charge transport mechanism in the studied PIL includes contributions from both the vehicular and Grotthus mechanisms. The protic ionic liquid is thermally stable to about 573 K as shown by thermogravimetric analysis and its electrical conductivity is 5 × 10-2 S/cm at 423 K.

A Joint Experimental and Theoretical Study on the Structural and Spectroscopic Properties of the Piv-Pro-d-Ser-NHMe Peptide.

In this paper, we investigate the secondary structure of the Piv-Pro-d-Ser-NHMe peptide by means of nuclear magnetic resonance (NMR) and electronic circular dichroism (ECD) experiments, in conjunction with theoretical simulations based on molecular dynamics and time-dependent density functional theory calculations including polarizable embedding to account for solvent effects. The various experimental and theoretical protocols are assessed and validated, and are shown to provide a consistent description of the turn structure adopted by this peptide in solution. In addition, a simple fitting procedure is proposed to make the simulated and experimental ECD almost perfectly match. This full methodology is finally tested on another small peptide, enlightening its efficiency and robustness.

Exploring galectin interactions with human milk oligosaccharides and blood group antigens identifies BGA6 as a functional galectin-4 ligand

Galectins (Gals), a family of multifunctional glycan-binding proteins, have been traditionally defined as β-galactoside binding lectins. However, certain members of this family have shown selective affinity towards specific glycan structures including human milk oligosaccharides (HMOs) and blood group antigens. In this work, we explored the affinity of human galectins (particularly Gal-1, -3, -4, -7 and -12) towards a panel of oligosaccharides including HMOs and blood group antigens using a complementary approach based on both experimental and computational techniques. While prototype Gal-1 and Gal-7 exhibited differential affinity for type I vs. type II Lac/LacNAc residues and recognized fucosylated neutral glycans, chimera-type Gal-3 showed high binding affinity towards poly-LacNAc structures including LNnH and LNnO. Notably, the tandem-repeat human Gal-12 showed preferential recognition of 3-fucosylated glycans, a unique feature among members of the galectin family. Finally, Gal-4 presented a distinctive glycan-binding activity characterized by preferential recognition of specific blood group antigens, also validated by saturation transfer difference nuclear magnetic resonance (STD-NMR) experiments. Particularly, we identified oligosaccharide blood group A type 6 (BGA6) as a biologically relevant Gal-4 ligand, which specifically inhibited IL-6 secretion induced by this lectin on human peripheral blood mononuclear cells. These findings highlight unique determinants underlying specific recognition of HMOs and blood group antigens by human galectins, emphasizing the biological relevance of Gal-4-BGA6 interactions, with critical implications in the development and regulation of inflammatory responses.

Perturbations in mitochondrial metabolism associated with defective cardiolipin biosynthesis: An in-organello real-time NMR study.

Mitochondria are central to cellular metabolism; hence, their dysfunction contributes to a wide array of human diseases including cancer, cardiopathy, neurodegeneration, and heritable pathologies such as Barth syndrome. Cardiolipin, the signature phospholipid of the mitochondrion promotes proper cristae morphology, bioenergetic functions, and directly affects metabolic reactions carried out in mitochondrial membranes. To match tissue-specific metabolic demands, cardiolipin typically undergoes an acyl tail remodeling process with the final step carried out by the phospholipid-lysophospholipid transacylase tafazzin. Mutations in the tafazzin gene are the primary cause of Barth syndrome. Here, we investigated how defects in cardiolipin biosynthesis and remodeling impact metabolic flux through the tricarboxylic acid cycle and associated pathways in yeast. Nuclear magnetic resonance was used to monitor in real-time the metabolic fate of 13C3-pyruvate in isolated mitochondria from three isogenic yeast strains. We compared mitochondria from a wild-type strain to mitochondria from a Δtaz1 strain that lacks tafazzin and contains lower amounts of unremodeled cardiolipin, and mitochondria from a Δcrd1 strain that lacks cardiolipin synthase and cannot synthesize cardiolipin. We found that the 13C-label from the pyruvate substrate was distributed through about twelve metabolites. Several of the identified metabolites were specific to yeast pathways, including branched chain amino acids and fusel alcohol synthesis. Most metabolites showed similar kinetics amongst the different strains but mevalonate and α-ketoglutarate, as well as the NAD+/NADH couple measured in separate nuclear magnetic resonance experiments, showed pronounced differences. Taken together, the results show that cardiolipin remodeling influences pyruvate metabolism, tricarboxylic acid cycle flux, and the levels of mitochondrial nucleotides.

Quantitative Antioxidant Profiling Throughout Beer Brewing Followed by Discovery and Isolation of Precursors from Barley (Hordeum vulgare L.).

The application of high-performance liquid chromatography-mass spectrometry (HPLC-MS/MS) revealed the origin and evolution of antioxidants during the brewing process of hopped and unhopped reference beer. As tachioside (3-methoxy-4-hydroxyphenyl-β-d-glucopyranoside), arbutin (4-hydroxyphenyl-β-d-glucopyranoside), and hordatines clearly increased during the fermentation step, the raw material barley was investigated as a source of the corresponding precursors. Therefore, 4-hydroxyphenyl-β-d-glucopyranosyl-(1 → 6)-β-d-glucopyranosyl-(1 → 6)-β-d-glucopyranoside, 4-hydroxy-3-methoxyphenyl-β-d-glucopyranosyl-(1 → 6)-β-d-glucopyranoside, 4-hydroxy-3-methoxyphenyl-β-d-glucopyranosyl-(1 → 6)-β-d-glucopyranosyl-(1 → 6)-β-d-glucopyranoside, and 4-hydroxy-2-methoxyphenyl-β-d-glucopyranosyl-(1 → 6)-β-d-glucopyranosyl-(1 → 6)-β-d-glucopyranoside were isolated from barley for the first time, and identified using liquid chromatography-mass spectrometry (LC-MS) and one-dimensional/two-dimensional-nuclear magnetic resonance (1D/2D-NMR) experiments. Moreover, hordatine glucosides A, B, and C were isolated and identified from barley, and hordatine C glucoside was characterized for the first time. A fermentation model followed by HPLC-MS/MS analysis substantiated the release of tachioside from 4-hydroxy-3-methoxyphenyl-β-d-glucopyranosyl-(1 → 6)-β-d-glucopyranoside by Saccharomyces cerevisiae. Quantitation experiments monitoring the content in wheat, barley, and different barley malt types demonstrated a wide range of concentrations, providing a basis for further comprehensive investigations to optimize the antioxidant yield in beer to contribute to improved flavor stability.

Probing structural features in potato starch granules at moderate hydration through the modelling of 1H->13C polarization transfer kinetics

The structural arrangement of starch polymers in presence of water is known to impact the functional properties of starchy products. In this study, the hydration of potato starch granules was investigated at the molecular level through various 1H->13C polarization transfer solid-state Nuclear Magnetic Resonance (ss-NMR) experiments. The impact of increasing the water content from 12.3 % to 45.9 % was assessed using 13C Cross Polarization Magic Angle Spinning (CPMAS), Variable Contact Time (VCT-CPMAS), Variable Spin Lock (VSL-CPMAS), and T One Rho QUEnching (TORQUE) NMR sequences. Of these, VCT-CPMAS proved to be the most promising. When applied with an optimal number of contact times, it enabled the application of several mathematical models that provided detailed insights into the structuring of protons in the hydrated potato starch granules. At low hydration (12.3 %), the models enabled various structural domains to be distinguished, which we suggest are associated with helical and amorphous structures. At moderate hydration (45.9 %), we tested two fitting models. Two pools of protons were revealed, corresponding to loosely ordered structures on the scale of tens of nanometers. These findings suggest varying water distribution during starch hydration and are likely to indicate variable hydration levels in the multilamellar amorphous structures of starch granules.

Covalent Binding of Reactive Anhydride of Cantharidin to Biological Amines.

Cantharidin is a terpenoid from coleoptera beetles. Cantharidin has been used to treat molluscum contagiosum and some types of tumors. Cantharidin is highly toxic, and cantharidin poisoning and fatal cases have been reported worldwide. The mechanisms underlying cantharidin-induced toxicity remain unclear. Cantharidin contains anhydride, which may react with biologic amines. This study aimed to examine the chemical reactivity of cantharidin toward nucleophiles and characterize adducts of cantharidin with biologic amines in vitro and in mice. Here two types of conjugates were formed in the incubation of cantharidin under physiologic conditions with free amino acids, a mimic peptide, or amine-containing compounds, respectively. Amide-type conjugates were produced by the binding of cantharidin anhydride with the primary amino group of biologic amines. Imide-type conjugates were generated from the dehydration and cyclization of amide-type conjugates. The structure of the conjugates was characterized by using high-resolution mass spectrometry. We introduced the 14N/15N and 79Br/81Br isotope signatures to confirm the formation of conjugates using L-(ε)15N-lysine, L-lysine-15N2, and bromine-tagged hydrazine, respectively. The structure of imide conjugate was also confirmed by nuclear magnetic resonance experiments. Furthermore, the amide and imide conjugates of cantharidin with amino acids or N-acetyl-lysine were detected in mouse liver and urine. Cantharidin was found to modify lysine residue proteins in mouse liver. Pan-cytochrome P450 inhibitor 1-aminobenzotriazole significantly increased the urine cantharidin-N-acetyl-lysine conjugates, whereas it decreased cantharidin metabolites. In summary, cantharidin anhydride can covalently bind to biologic amines nonenzymatically, which facilitates a better understanding of the role of nonenzymatic reactivity in cantharidin poisoning. SIGNIFICANCE STATEMENT: Anhydride moiety of cantharidin can covalently bind to the primary amino group of biological amines nonenzymatically. Amide and imide conjugates were generated after the covalent binding of cantharidin anhydride with the primary amino groups of amino acids, a mimic peptide, and protein lysine residues. The structure of conjugates was confirmed by 14N/15N and 79Br/81Br isotope signatures using isotope-tagged reagents and nuclear magnetic resonance experiments. This study will facilitate the understanding of the role of nonenzymatic reactivity in cantharidin poisoning.

Molecular Dynamics Simulation of Methane Adsorption and Diffusion

To study the adsorption and diffusion mechanism of low-rank coal at the microscopic level, samples of Fukang low-rank coal were collected, and the elemental composition, carbon type distribution and functional group type of the Fukang low-rank coal structure were determined by elemental analysis (Ea), Fourier-transform interferometric radiometer (FTIR), X-ray photoelectron spectroscopy (XPS) and 13C nuclear magnetic resonance (13C NMR) experiments to construct a 2D molecular structure of the coal and a 3D macromolecular structure model. The adsorption and diffusion characteristics of methane were researched by giant regular Monte Carlo (GCMC) and molecular dynamics (MD) simulation methods. The results showed that the excess adsorption amount of methane increased and then decreased with the increase in pressure. The diffusion of methane showed two stages with increasing pressure: a sharp decrease in the diffusion coefficient from 0.5 to 5.0 MPa and a slow decrease in the diffusion coefficient from 5.0 to 15.0 MPa. The lower the pressure, the larger the effective radius of the CH4 and C atoms, and the higher the temperature, the more pronounced the diffusion and the larger the effective radius.

New Monoterpenoid as the Sex Pheromone of Spanish Populations of the Longtailed Mealybug Pseudococcus Longispinus (Hemiptera: Pseudococcidae).

Pseudococcus longispinus (Targioni-Tozzetti) (Hemiptera: Coccoidea: Pseudococcidae), a polyphagous and cosmopolitan pest native to Australia, is a highly damaging pest for numerous crops of economic importance. The sex pheromone of this species (2-(1,5,5-trimethylcyclopent-2-en-1-yl)ethyl acetate), currently used for pest monitoring purposes, was not attractive to males in field experiments conducted in Spanish persimmon orchards infested with this mealybug. The virgin and mated female volatile profiles of these P. longispinus populations were studied by the volatile collection of effluvia in Porapak-Q. The resulting extracts were analyzed by gas chromatography coupled to mass spectrometry (GC-MS), revealing a new compound specific to virgin females and different from the previously described sex pheromone. Based on GC-MS data and nuclear magnetic resonance experiments, we envisaged monoterpene 2-(1,5-dimethyl-4-methylenecyclopent-2-en-1-yl)ethyl acetate as the new sex pheromone candidate, which was synthesized and shown to be attractive in the field to P. longispinus males of the Spanish population.

Single-Scan Heteronuclear 13C-15N J-Coupling NMR Observations Enhanced by Dissolution Dynamic Nuclear Polarization.

Heteronuclear 13C-15N couplings were measured in single-scan nuclear magnetic resonance (NMR) experiments for a variety of nitrogen-containing chemical compounds with varied structural characteristics, by using a one-dimensional (1D) 13C-15N multiple-quantum (MQ)-filtered experiment. Sensitivity limitations of the MQ filtering were overcome by the combined use of 15N labeling and dissolution dynamic nuclear polarization (dDNP), performed at cryogenic conditions and followed by quick and optimized sample melting and transfer procedures. Coupling information could thus be obtained from nucleotide bases, amino acids, urea, and aliphatic and aromatic amides, including the measurement of relatively small J-couplings directly from the 1D filtered spectra. This experiment could pave the way for NMR-based analytical applications that investigate structural and stereochemical insights into nitrogen-containing compounds, including dipeptides and proteins, while relying on heteronuclear couplings and nuclear hyperpolarization.

Chemical reaction driven self-assembly of a nucleobase functionalized molecule

Molecular self-assembly is an important aspect in the nano technology and nano science which is exploited to produce complex supramolecular nanoarchitectures. Different strategies are used to achieve the molecular self-assembly in the laboratory. Here, the methylation reaction is used to induce the supramolecular order in the synthesized guanine functionalized molecules. Methylation is an important biological process which is used for DNA methylation. The methylation reaction driven formation of higher order self-assembly is discussed. The formation of the activated building blocks is studied using high-performance liquid chromatography. The N7 methylation is observed majorly. The pH of the medium is decreased with the progress of the reaction. The progress of self-assembly upon the addition of dimethyl sulphate is monitored by fluorescence, circular dichroism spectroscopy, 1H nuclear magnetic resonance and turbidity experiments. Additionally, Thioflavin T dye binding, wide-angle powder X-ray diffraction, circular dichroism spectroscopy experiments are performed to establish the formation of the chemical reaction driven self-assembled hydrogel. The formation of the nanofiber inside the hydrogel is confirmed by performing various microscopic experiments.

Determination of Acetylamantadine by γ-Cyclodextrin-Assisted α-HL Nanopore for Potential Cancer Prediagnosis.

The high expression of Spermidine/spermine N1-acetyltransferase (SSAT-1) is an important indicator in early cancer diagnosis. Here, we developed a nanopore-based methodology with γ-cyclodextrin as an adaptor to detect and quantify acetylamantadine, the specific SSAT-1-catalyzed product from amantadine, to accordingly reflect the activity of SSAT-1. We employ γ-cyclodextrin and report that amantadine cannot cause any secondary signals in γ-cyclodextrin-assisted α-HL nanopore, while its acetylation product, acetylamantadine, does. This allows γ-cyclodextrin to practically detect acetylamantadine in the interference of excessive amantadine, superior to the previously reported β-cyclodextrin. The quantification of acetylamantadine was not interfered with even a 50-fold amantadine and displayed no interference in artificial urine sample analysis, which indicates the good feasibility of this nanopore-based methodology in painless cancer prediagnosis. In addition, the discrimination mechanism is also explored by 2-D nuclear magnetic resonance (NMR) and nanopore experiments with a series of adamantane derivatives with different hydrophilic and hydrophobic groups. We found that both the hydrophobic region matching effect and hydrophilic interactions play a synergistic effect in forming a host-guest complex to further generate the characteristic signals, which may provide insights for the subsequent design and study of drug-cyclodextrin complexes.

A Joint Inversion Method Algorithm for T2-Pc two Dimensional NMR based on Logistic Functions

Data processing is a key step in the analysis of nuclear magnetic resonance (NMR) experimental data, and efficient and accurate computer inversion algorithms are the core of the T2-Pc two-dimensional NMR experiment. T2-Pc two-dimensional NMR experiment is an advanced experimental method that characterizes reservoir connectivity through two dimensions: relaxation time and capillary pressure, and can obtain irreducible water saturation under different pressure differences. However, the algorithm currently used for T2-Pc two-dimensional spectrum inversion uses a mutation kernel function, resulting in low accuracy of calculation results. This paper uses the Logistic function as the two-dimensional inversion kernel function, rewrites the inversion algorithm, and obtains more accurate inversion results. Numerical simulations have proven that the T2-Pc two-dimensional map obtained by this method not only has higher resolution, but also has greater applicability in the case of low signal-to-noise ratio and a small number of centrifugal echo groups. Practice has found that the proposed method can reduce the number of centrifugations during the experiment and significantly improve the efficiency of T2-Pc two-dimensional nuclear magnetic resonance experiments.

Mechanism analysis of injection technique of water composition modification for enhanced oil recovery

ABSTRACT By adjusting the composition of injection water, including ionic type and strength, the goal of enhance oil recovery rate can be achieved. However, there is no clear understanding of which factor, ionic type or strength, has a greater impact. In this paper, based on the formation water of the offshore G oilfield, various brines with different ionic strengths and types were prepared. By measuring the zeta potential of rock powder and oil droplets, three-phase contact angle, interfacial tension between oil and water, emulsification properties of brines, and film strength of oil-water interface, the variation rules of the core wettability and emulsification performance of brine were systematically analyzed when the ionic strength and ionic type were changed. The experimental results showed that ionic strength has a greater impact than that of ionic type. For the oil-water-solid (rock) system of the G oilfield, an ionic strength of 82 mM/kg is the threshold for low salinity effect. Reducing ionic strength resulted in an increase in the hydrophilicity of rock and the ability of water flooding to emulsify oil droplets, which contribute to the improvement of oil displacement efficiency. Theoretically, water flooding to enhance oil recovery can be achieved by only reducing the ionic strength. This understanding was verified by dual polarization interferometry (DPI) experiments and low-field nuclear magnetic resonance experiments, which showed that reducing the salinity of the injection water from 42,000 mg/L (ionic strength of 820 mM/kg) to 4200 mg/L (ionic strength of 82 mM/kg) enhanced the oil recovery by 7.9%.

Experimental investigation of geometric quantum speed limits in an open quantum system

The quantum speed limit (QSL) is a fundamental lower bound on the evolution time for quantum systems, and its tightness has been observed to be dependent on the properties of the physical process. However, experimental studies exploring the QSL in open quantum systems are still missing. Here, we studied geometric quantum speed limits of a qubit subject to decoherence in an ensemble of chloroform molecules in a Nuclear Magnetic Resonance experiment. We controlled the system-reservoir interaction and the spin relaxation rates by adding a paramagnetic salt, allowing the observation of both Markovian and non-Markovian open system dynamics for the qubit. We used two distinguishability measures of quantum states to assess the speed of the qubit evolution: the quantum Fisher information (QFI) and Wigner-Yanase skew information (WY). For non-Markovianity and low salt concentrations, we found crossovers between QSLs related to those metrics. The WY metric sets the tighter QSL for high concentrations and Markovian dynamics. We also show that QSLs are sensitive even to small fluctuations in spin magnetization.

Red Shift in the Absorption Spectrum of Phototropin LOV1 upon the Formation of a Semiquinone Radical: Reconstructing the Orbital Architecture.

Flavin mononucleotide (FMN) is a ubiquitous blue-light pigment due to its ability to drive one- and two-electron transfer reactions. In both light-oxygen-voltage (LOV) domains of phototropin from the green algae Chlamydomonas reinhardtii, FMN is noncovalently bound. In the LOV1 cysteine-to-serine mutant (C57S), light-induced electron transfer from a nearby tryptophan occurs, and a transient spin-correlated radical pair (SCRP) is formed. Within this photocycle, nuclear hyperpolarization is created by the solid-state photochemically induced dynamic nuclear polarization (photo-CIDNP) effect. In a side reaction, a stable protonated semiquinone radical (FMNH·) forms undergoing a significant bathochromic shift of the first electronic transition from 445 to 591 nm. The incorporation of phototropin LOV1-C57S into an amorphous trehalose matrix, stabilizing the radical, allows for application of various magnetic resonance experiments at ambient temperatures, which are combined with quantum-chemical calculations. As a result, the bathochromic shift of the first absorption band is explained by lifting the degeneracy of the molecular orbital energy levels for electrons with alpha and beta spins in FMNH· due to the additional electron.

A modular library for fast prototyping of solution-state nuclear magnetic resonance experiments

Abstract. We present a framework library (Modular Elements, ME) for the development of pulse sequences for Bruker spectrometers. It implements a two-level abstraction approach – the lower level comprises basic functional elements of pulse sequences and the higher one often-reused blocks comprising several evolution periods. The low-level abstractions reduce code duplication between variants of experiments such as hard-pulse and selective variants of individual NMR experiments. The high-level modules enable further reuse of pulse program code and aid in the construction of complex experiments. We show the library's functionality by presenting pulse programs that can be switched between standard and TROSY variants as well as hard and shaped pulses and that can seamlessly incorporate real-time homodecoupling. Adaptability is further demonstrated in a configurable 4D NOESY program.