NMR Lineshapes and Scalar Relaxation of the Water-Endofullerene H217 O@C60

Intraocular Water Movement Visualization Using 1 H-MRI With Eye Drops of O-17-Labeled Saline: First-in-Human Study

BACKGROUND

Visualization of aqueous humor flow in MR contrast images using gadolinium is challenging because of the delayed contrast effects associated with the blood-retinal and blood-aqueous humor barriers. However, oxygen-17 water (H₂ ¹⁷ O) might be used as an ocular contrast agent.

PURPOSE

To observe the distribution of H₂ ¹⁷ O in the human eye, and its flow in and out of the anterior chamber, using dynamic T2-weighted MRI.

STUDY TYPE

Prospective.

POPULATION

Six ophthalmologically normal volunteers (20-37 years, six females).

FIELD STRENGTH/SEQUENCE

A 3 T/dynamic T2-weighted MRI.

ASSESSMENT

H₂ ¹⁷ O eye drops were administered to the right eye. Time-series images were created by subtracting the image before the eye drops from each of the images obtained after the eye drops. The normalized signal intensity of the right anterior chamber (nAC) was obtained by dividing the signal intensity of the right anterior chamber region by that of the left. The inflow and outflow constants of H₂ ¹⁷ O and H₂ ¹⁷ O concentration were calculated from the nAC.

STATISTICAL TESTS

A paired t-test was used to compare the flow-related values and temporal changes in signal intensity. P-values < 0.05 were considered statistically significant.

RESULTS

Significantly decreased signal intensity was observed in the right anterior chamber but not the right vitreous body (P = 0.39). The nAC signal intensity decreased significantly and then recovered. The inflow and outflow constants were 0.36-0.94 min^-1 and 0.023-0.13 min^-1 , respectively. The maximum H₂ ¹⁷ O concentration was 0.078%-0.24%.

DATA CONCLUSION

H₂ ¹⁷ O were distributed in the anterior chamber. The H₂ ¹⁷ O inflow into the anterior chamber was significantly faster than that of the outflow.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY STAGE: 2.

High-field ex vivo and in vivo two-dimensional nuclear magnetic resonance spectroscopy in murine brain: Resolving and exploring the molecular environment

The structural and chemical complexities within the brain pose a challenge that few noninvasive techniques can tackle with the dexterity of nuclear magnetic resonance (NMR) spectroscopy. Still, even with the advent of ultrahigh fields and of cryogenically cooled coils for in vivo research, the superposition of metabolic resonances arising from the brain remains a challenge. The present study explores the potential to tackle this milieu using a combination of two-dimensional (2D) NMR techniques, implemented on murine brains in vivo at 15.2 T and ex vivo at 14.1 T. While both experiments were affected by substantial inhomogeneous broadenings conveying distinct elongated lineshapes to the cross-peaks, the ability of increased fields to resolve off-diagonal resonances was clear. A comparison between the corresponding conventional and double quantum-filtered correlated spectroscopy traces enabled an improved assignment of in vivo resonances on the basis of more sensitive ex vivo 2D acquisitions, foremost on the basis of homonuclear cross-relaxation-driven correlations for peaks resonating downfield from water, and of heteronuclear correlations at natural abundance for the upfield protons. With the aid of such 2D correlations approximately 29 metabolites could be resolved and identified. This enhanced resolution was used to explore features related to the metabolites' diffusivities, their exposure to water, and their facility to undergo magnetization transfers to amide/amine/hydroxyl resonances. Cross-peaks from main murine brain biomolecules, including choline, creatine, γ-aminobutyric acid, N-acetyl aspartate, glutamine, and glutamate, showed enhancements in several of these various features, opening interesting vistas about metabolite compartmentalization as viewed by these 2D NMR experiments.

Unraveling the Origin of Symmetry Breaking in H2 O@C60 Endofullerene Through Quantum Computations

We explore the origin of the anomalous splitting of the 101 levels reported experimentally for the H2 O@C60 endofullerene, in order to give some insight about the physical interpretations of the symmetry breaking observed. We performed fully-coupled quantum computations within the multiconfiguration time-dependent Hartree approach employing a rigorous procedure to handle such computationally challenging problems. We introduce two competing physical models, and discuss the observed unconventional quantum patterns in terms of anisotropy in the interfullerene interactions, caused by the change in the off-center position of the encapsulated water molecules inside the cage or the uniaxial C60 -cage distortion, arising from noncovalent bonding upon water's encapsulation, or exohedral fullerene perturbations. Our results show that both scenarios could reproduce the experimentally observed rotational degeneracy pattern, although quantitative agreement with the available experimental rotational levels splitting value has been achieved by the model that considers an uniaxial elongation of the C60 -cage. Such finding supports that the observed symmetry breaking could be mainly caused by the distortion of the fullerene cage. However, as nuclear quantum treatments rely on the underlying interactions, a decisive conclusion hinges on the availability of their improved description, taken into account both endofullerene and exohedral environments, from forthcoming highly demanding electronic structure many-body interaction studies.

In vivo Human MR Spectroscopy Using a Clinical Scanner: Development, Applications, and Future Prospects

MR spectroscopy (MRS) is a unique and useful method for noninvasively evaluating biochemical metabolism in human organs and tissues, but its clinical dissemination has been slow and often limited to specialized institutions or hospitals with experts in MRS technology. The number of 3-T clinical MR scanners is now increasing, representing a major opportunity to promote the use of clinical MRS. In this review, we summarize the theoretical background and basic knowledge required to understand the results obtained with MRS and introduce the general consensus on the clinical utility of proton MRS in routine clinical practice. In addition, we present updates to the consensus guidelines on proton MRS published by the members of a working committee of the Japan Society of Magnetic Resonance in Medicine in 2013. Recent research into multinuclear MRS equipped in clinical MR scanners is explained with an eye toward future development. This article seeks to provide an overview of the current status of clinical MRS and to promote the understanding of when it can be useful. In the coming years, MRS-mediated biochemical evaluation is expected to become available for even routine clinical practice.

Noncovalently bound molecular complexes beyond diatom–diatom systems: full-dimensional, fully coupled quantum calculations of rovibrational states

The methodological advances made in recent years have significantly extended the range and dimensionality of noncovalently bound molecular complexes for which full-dimensional quantum calculations of their rovibrational states are feasible.

CO2 Activation Within a Superalkali-Doped Fullerene

With the aim of finding a suitable synthesizable superalkali species, using the B3LYP/6-31G* density functional level of theory we provide results for the interaction between the buckminsterfullerene C60 and the superalkali Li3F2. We show that this endofullerene is stable and provides a closed environment in which the superalkali can exist and interact with CO2. It is worthwhile to mention that the optimized Li3F2 structure inside C60 is not the most stable C2v isomer found for the "free" superalkali but the D3h geometry. The binding energy at 0 K between C60 and Li3F2 (D3h) is computed to be 119 kJ mol-1. Once CO2 is introduced in the endofullerene, it is activated, and theO C O ^ angle is bent to 132°. This activation does not follow the previously studied CO2 reduction by an electron transfer process from the superalkali, but it is rather an actual reaction where a F (from Li3F2) atom is bonded to the CO2. From a thermodynamic analysis, both CO2 and the encapsulated [Li3F2⋅CO2] are destabilized in C60 with solvation energies at 0 K of 147 and < -965 kJ mol-1, respectively.

Rotational coherence of encapsulated ortho and para water in fullerene-C60 revealed by time-domain terahertz spectroscopy

We resolve the real-time coherent rotational motion of isolated water molecules encapsulated in fullerene-C60 cages by time-domain terahertz (THz) spectroscopy. We employ single-cycle THz pulses to excite the low-frequency rotational motion of water and measure the subsequent coherent emission of electromagnetic waves by water molecules. At temperatures below ~ 100 K, C60 lattice vibrational damping is mitigated and the quantum dynamics of confined water are resolved with a markedly long rotational coherence, extended beyond 10 ps. The observed rotational transitions agree well with low-frequency rotational dynamics of single water molecules in the gas phase. However, some additional spectral features with their major contribution at ~2.26 THz are also observed which may indicate interaction between water rotation and the C60 lattice phonons. We also resolve the real-time change of the emission pattern of water after a sudden cooling to 4 K, signifying the conversion of ortho-water to para-water over the course of 10s hours. The observed long coherent rotational dynamics of isolated water molecules confined in C60 makes this system an attractive candidate for future quantum technology.

Rotational-permutational dual-pairing and long-lived spin order

Quantum systems in contact with a thermal environment experience coherent and incoherent dynamics. These drive the system back toward thermal equilibrium after an initial perturbation. The relaxation process involves the reorganization of spin state populations and the decay of spin state coherences. In general, individual populations and coherences may exhibit different relaxation time constants. Particular spin configurations may exhibit exceptionally long relaxation time constants. Such spin configurations are known as long-lived spin order. The existence of long-lived spin order is a direct consequence of the symmetries of the system. For nuclear spin systems, rotational and permutational symmetries are of fundamental importance. Based on the Schur-Weyl duality theorem, we describe a theoretical framework for the study of rotational and permutational dual-symmetries in the context of long-lived spin order. Making use of the proposed formalism, we derive refined bounds on the number on long-lived spin populations and coherences for systems exhibiting rotational-permutational dual-symmetries.

A master equation for spin systems far from equilibrium

The quantum dynamics of spin systems is often treated by a differential equation known as the master equation, which describes the trajectories of spin observables such as magnetization components, spin state populations, and coherences between spin states. The master equation describes how a perturbed spin system returns to a state of thermal equilibrium with a finite-temperature environment. The conventional master equation, which has the form of an inhomogeneous differential equation, applies to cases where the spin system remains close to thermal equilibrium, which is well satisfied for a wide variety of magnetic resonance experiments conducted on thermally polarized spin systems at ordinary temperatures. However, the conventional inhomogeneous master equation may fail in the case of hyperpolarized spin systems, when the spin state populations deviate strongly from thermal equilibrium, and in general where there is a high degree of nuclear spin order. We highlight a simple case in which the inhomogeneous master equation clearly fails, and propose an alternative master equation based on Lindblad superoperators which avoids most of the deficiencies of previous proposals. We discuss the strengths and limitations of the various formulations of the master equation, in the context of spin systems which are far from thermal equilibrium. The method is applied to several problems in nuclear magnetic resonance and to spin-isomer conversion.

Tuber extract of Arisaema flavum eco-benignly and effectively synthesize silver nanoparticles: Photocatalytic and antibacterial response against multidrug resistant engineered E. coli QH4

Metal nanoparticles, synthesized using Phyto-constituents are the most economically and environmentally benign materials ever. Biogenic silver nanoparticles (AgNPs) from three fractions of Arisaema flavum tuber extract were synthesized and characterized by UV-visible spectroscopy, XRD (X-rays diffraction), FT-IR (Fourier transform infrared spectroscopy) TEM (transmission electron microscopy) and EDX (Energy dispersive Microscopy). XRD pattern show the face centred cubic crystalline (Fcc) structure of AgNPs. FTIR spectra confirmed the presence of different Polyphenolic compounds capping the AgNps. UV-visible spectroscopy result confirmed the presence of Ag because of the particular surface plasmon Resonance (SPR) in the area of 400-430 nm. The electron microscope studies revealed the formation of spherical AgNPs with diameter ranging from 12 nm to 20 nm. Strong signals of AgNPs were confirmed with EDX analysis. The antibacterial properties of the AgNPs prepared with various extracts were tested against multi-drug resistant bacteria. Which showed significant antibacterial activity against all the multidrug resistant bacterial strains and especially multidrug resistant engineered E.ColiQH4. AgNPs synthesized by methanolic, Ethyl Acetate and aqueous Extracts of Areseama Flavum exhibited significant Photocatalytic activity to reduce methylene blue. Small size, spherical shape and high dispersion are the key properties due to which the AgNPs are having significant biological and photocatalytic activity. To the best of our knowledge, it is the first report of biogenic AgNPs regarding antibacterial activity against multidrug resistant Engineered E.Coli QH4.

17O and 1H NMR spectral parameters in isolated water molecules

Small amounts of water enriched in oxygen-17 were studied by 17O and 1H NMR in binary gaseous mixtures with Xe, Kr, CHF3 and CH3F and CO2. The distinct linear dependences of 17O and 1H chemical shifts and 1J(17O,1H) spin-spin coupling on the density of every gas solvent were measured. After the extrapolation of experimental results to zero density the relevant parameters in the isolated H217O molecule were determined. The same procedure was applied for H216O when its proton chemical shift was analyzed but the secondary isotope effect in the 1H shielding of H217O and H216O molecules was too small for detection. As shown, all the intermolecular effects in nuclear magnetic shielding are negative and these effects are more significant for 17O nuclei than for protons. It is consistent with the appropriate gas-to-liquid shifts of water which also indicate deshielding effects for both the investigated nuclei. On the other hand, the 1J0(17O,1H) coupling constant in H217O, which is completely free from intermolecular interactions, considerably differs from the 1J(17O,1H) experimental values obtained for water in liquid solutions. The present experimental data of the isolated H217O molecule are compared with selected results of shielding and spin-spin coupling calculations available from the literature and with the recent experimental data for a water molecule encapsulated in the C60 fullerene. Additionally, on the basis of actual results the magnetic dipole moment of the 17O nucleus is revalued for greater accuracy.

Quantum-rotor-induced polarization

Quantum-rotor-induced polarization is closely related to para-hydrogen-induced polarization. In both cases, the hyperpolarized spin order derives from rotational interaction and the Pauli principle by which the symmetry of the rotational ground state dictates the symmetry of the associated nuclear spin state. In quantum-rotor-induced polarization, there may be several spin states associated with the rotational ground state, and the hyperpolarization is typically generated by hetero-nuclear cross-relaxation. This review discusses preconditions for quantum-rotor-induced polarization for both the 1-dimensional methyl rotor and the asymmetric rotor H₂¹⁷ O@C₆₀ , that is, a single water molecule encapsulated in fullerene C₆₀ . Experimental results are presented for both rotors.

Spin-Isomer Conversion of Water at Room Temperature and Quantum-Rotor-Induced Nuclear Polarization in the Water-Endofullerene H_{2}O@C_{60}

Water exists in two forms, para and ortho, that have nuclear spin states with different symmetries. Here we report the conversion of fullerene-encapsulated para water to ortho water. The enrichment of para water at low temperatures is monitored via changes in the electrical polarizability of the material. Upon rapid dissolution of the material in toluene the excess para water converts to ortho water. In H_{2}^{16}O@C_{60} the conversion leads to a slow increase in the NMR signal. In H_{2}^{17}O@C_{60} the conversion gives rise to weak signal enhancements attributed to quantum-rotor-induced nuclear spin polarization. The time constants for the para-to-ortho conversion of fullerene-encapsulated water in ambient temperature solution are estimated as 30±4  s for the ^{16}O isotopolog of water, and 16±3  s for the ^{17}O isotopolog.

Alignment of 17O-enriched water-endofullerene H2O@C60 in a liquid crystal matrix

We present a 17O and 1H NMR study of molecular endofullerene H2O@C60 dissolved in the nematic liquid crystal N-(4-methoxybenzylidene)-4-butylaniline (MBBA). The 17O NMR peak is split into five components by the 17O residual quadrupolar coupling, each of which is split into a triplet by the 1H-17O residual dipolar coupling and scalar coupling. The splittings are analysed in terms of the partial alignment of the encapsulated water molecules. Order parameters describing the alignment are estimated. It is found that the preferential orientation of the endohedral water molecule has the molecular plane perpendicular to the liquid crystal director.