Watch-sized 12 Tesla all-high-temperature-superconducting magnet.

We demonstrate the construction of 7 Tesla and 12 Tesla all high-temperature-superconducting (HTS) magnets, small enough to fit on your wrist. The size of the magnet reduces the cost of fabrication, decreases the fringe field to permit facile siting of magnets, and decreases the stored energy of high field magnets. These small HTS-based magnets are being developed for gyrotron microwave sources for use in high-field nuclear magnetic resonance applications. The 7 Tesla and 12 Tesla magnets employ a no-insulation winding technique and are cooled to 4.2 Kelvin in a liquid helium cryostat. The 7 Tesla magnet is a single pancake coil, made of only 9.4 m of HTS tape, with an inner diameter of 8 mm and an outer diameter of 24 mm. This magnet was charged up to 1168 Amperes, generating a field of 7.3 Tesla. The 12 Tesla magnet is comprised of two pancake coils (inner diameter of 10 mm and outer diameter of 27 mm) connected in series. This magnet reached its maximum field at a current of 850 Amperes.

Nature of GaOx Shells Grown on Silica by Atomic Layer Deposition.

Gallia-based shells with a thickness varying from a submonolayer to ca. 2.5 nm were prepared by atomic layer deposition (ALD) using trimethylgallium, ozone, and partially dehydroxylated silica, followed by calcination at 500 °C. Insight into the atomic-scale structure of these shells was obtained by high-field 71Ga solid-state nuclear magnetic resonance (NMR) experiments and the modeling of X-ray differential pair distribution function data, complemented by Ga K-edge X-ray absorption spectroscopy and 29Si dynamic nuclear polarization surface enhanced NMR spectroscopy (DNP SENS) studies. When applying one ALD cycle, the grown submonolayer contains mostly tetracoordinate Ga sites with Si atoms in the second coordination sphere ([4]Ga(Si)) and, according to 15N DNP SENS using pyridine as the probe molecule, both strong Lewis acid sites (LAS) and strong Brønsted acid sites (BAS), consistent with the formation of gallosilicate Ga-O-Si and Ga-µ2-OH-Si species. The shells obtained using five and ten ALD cycles display characteristics of amorphous gallia (GaOx), i.e., an increased relative fraction of pentacoordinate sites ([5]Ga(Ga)), the presence of mild LAS, and a decreased relative abundance of strong BAS. The prepared Ga1-, Ga5-, and Ga10-SiO2-500 materials catalyze the dehydrogenation of isobutane to isobutene, and their catalytic performance correlates with the relative abundance and strength of LAS and BAS, viz., Ga1-SiO2-500, a material with a higher relative fraction of strong LAS, is more active and stable compared to Ga5- and Ga10-SiO2-500. In contrast, related ALD-derived Al1-, Al5-, and Al10-SiO2-500 materials do not catalyze the dehydrogenation of isobutane and this correlates with the lack of strong LAS in these materials that instead feature abundant strong BAS formed via the atomic-scale mixing of Al sites with silica, leading to Al-µ2-OH-Si sites. Our results suggest that [4]Ga(Si) sites provide strong Lewis acidity and drive the dehydrogenation activity, while the appearance of [5]Ga(Ga) sites with mild Lewis activity is associated with catalyst deactivation through coking. Overall, the atomic-level insights into the structure of the GaOx-based materials prepared in this work provide a guide to design active Ga-based catalysts by a rational tailoring of Lewis and Brønsted acidity (nature, strength, and abundance).

Cryogenic-compatible spherical rotors and stators for magic angle spinning dynamic nuclear polarization.

Cryogenic magic angle spinning (MAS) is a standard technique utilized for dynamic nuclear polarization (DNP) in solid-state nuclear magnetic resonance (NMR). Here we describe the optimization and implementation of a stator for cryogenic MAS with 9.5 mm diameter spherical rotors, allowing for DNP experiments on large sample volumes. Designs of the stator and rotor for cryogenic MAS build on recent advancements of MAS spheres and take a step further to incorporate sample insert and eject and a temperature-independent spinning stability of ±1 Hz. At a field of 7 T and spinning at 2.0 kHz with a sample temperature of 105-107 K, DNP enhancements of 256 and 200 were observed for 124 and 223 µL sample volumes, respectively, each consisting of 4 M 13C, 15N-labeled urea and 20 mM AMUPol in a glycerol-water glassy matrix.

Active Site Descriptors from 95Mo NMR Signatures of Silica-Supported Mo-Based Olefin Metathesis Catalysts.

The olefin metathesis activity of silica-supported molybdenum oxides depends strongly on metal loading and preparation conditions, indicating that the nature and/or amounts of the active sites vary across compositionally similar catalysts. This is illustrated by comparing Mo-based (pre)catalysts prepared by impregnation (2.5-15.6 wt % Mo) and a model material (2.3 wt % Mo) synthesized via surface organometallic chemistry (SOMC). Analyses of FTIR, UV-vis, and Mo K-edge X-ray absorption spectra show that these (pre)catalysts are composed predominantly of similar isolated Mo dioxo sites. However, they exhibit different reaction properties in both liquid and gas-phase olefin metathesis with the SOMC-derived catalyst outperforming a classical catalyst of a similar Mo loading by ×1.5-2.0. Notably, solid-state 95Mo NMR analyses leveraging state-of-the-art high-field (28.2 T) measurement conditions resolve four distinct surface Mo dioxo sites with distributions that depend on the (pre)catalyst preparation methods. The intensity of a specific deshielded 95Mo NMR signal, which is most prominent in the SOMC-derived catalyst, is linked to reducibility and catalytic activity. First-principles calculations show that 95Mo NMR parameters directly manifest the local strain and coordination environment: acute (SiO-Mo(O)2-OSi) angles and low coordination numbers at Mo lead to highly deshielded 95Mo chemical shifts and small quadrupolar coupling constants, respectively. Natural chemical shift analyses relate the 95Mo NMR signature of strained species to low LUMO energies, which is consistent with their high reducibility and corresponding reactivity. The 95Mo chemical shifts of supported Mo dioxo sites are thus linked to their specific electronic structures, providing a powerful descriptor for their propensity toward reduction and formation of active sites.

Insertion Depth Modulates Protein Kinase C-δ-C1b Domain Interactions with Membrane Cholesterol as Revealed by MD Simulations.

Protein kinase C delta (PKC-δ) is an important signaling molecule in human cells that has both proapoptotic as well as antiapoptotic functions. These conflicting activities can be modulated by two classes of ligands, phorbol esters and bryostatins. Phorbol esters are known tumor promoters, while bryostatins have anti-cancer properties. This is despite both ligands binding to the C1b domain of PKC-δ (δC1b) with a similar affinity. The molecular mechanism behind this discrepancy in cellular effects remains unknown. Here, we have used molecular dynamics simulations to investigate the structure and intermolecular interactions of these ligands bound to δC1b with heterogeneous membranes. We observed clear interactions between the δC1b-phorbol complex and membrane cholesterol, primarily through the backbone amide of L250 and through the K256 side-chain amine. In contrast, the δC1b-bryostatin complex did not exhibit interactions with cholesterol. Topological maps of the membrane insertion depth of the δC1b-ligand complexes suggest that insertion depth can modulate δC1b interactions with cholesterol. The lack of cholesterol interactions suggests that bryostatin-bound δC1b may not readily translocate to cholesterol-rich domains within the plasma membrane, which could significantly alter the substrate specificity of PKC-δ compared to δC1b-phorbol complexes.

Electron-decoupled MAS DNP with N@C60.

Frequency-chirped microwaves decouple electron- and 13C-spins in magic-angle spinning N@C60:C60 powder, improving DNP-enhanced 13C NMR signal intensity by 12% for 7 s polarization, and 5% for 30 s polarization. This electron decoupling demonstration is a step toward utilizing N@C60 as a controllable electron-spin source for magic-angle spinning magnetic resonance experiments.

Solid-State NMR Spectra of Protons and Quadrupolar Nuclei at 28.2 T: Resolving Signatures of Surface Sites with Fast Magic Angle Spinning.

Advances in solid-state nuclear magnetic resonance (NMR) methods and hardware offer expanding opportunities for analysis of materials, interfaces, and surfaces. Here, we demonstrate the application of a very high magnetic field strength of 28.2 T and fast magic-angle-spinning rates (MAS, >40 kHz) to surface species relevant to catalysis. Specifically, we present as case studies the 1D and 2D solid-state NMR spectra of important catalyst and support materials, ranging from a well-defined silica-supported organometallic catalyst to dehydroxylated γ-alumina and zeolite solid acids. The high field and fast-MAS measurement conditions substantially improve spectral resolution and narrow NMR signals, which is particularly beneficial for solid-state 1D and 2D NMR analysis of 1H and quadrupolar nuclei such as 27Al at surfaces.

Antibiotic polymyxin arranges lipopolysaccharide into crystalline structures to solidify the bacterial membrane.

Polymyxins are last-resort antibiotics with potent activity against multi-drug resistant pathogens. They interact with lipopolysaccharide (LPS) in bacterial membranes, but mechanistic details at the molecular level remain unclear. Here, we characterize the interaction of polymyxins with native, LPS-containing outer membrane patches of Escherichia coli by high-resolution atomic force microscopy imaging, along with structural and biochemical assays. We find that polymyxins arrange LPS into hexagonal assemblies to form crystalline structures. Formation of the crystalline structures is correlated with the antibiotic activity, and absent in polymyxin-resistant strains. Crystal lattice parameters alter with variations of the LPS and polymyxin molecules. Quantitative measurements show that the crystalline structures decrease membrane thickness and increase membrane area as well as stiffness. Together, these findings suggest the formation of rigid LPS-polymyxin crystals and subsequent membrane disruption as the mechanism of polymyxin action and provide a benchmark for optimization and de novo design of LPS-targeting antimicrobials.

Improving the sensitivity of MAS spheres using a 9.5 mm spherical shell with 219 µL sample volume spinning in a spherical solenoid coil.

Spherical rotors in magic angle spinning (MAS) nuclear magnetic resonance (NMR) experiments have potential advantages relative to cylindrical rotors in terms of ease of fabrication, low risk of rotor crash, easy sample exchange, and better microwave access. However, one major disadvantage so far of spherical rotors is poor NMR filling factor due to the small sample volume and large cylindrical radiofrequency (RF) coil. Here we present a novel NMR coil geometry in the form of a spherical coil. The spherical coil best fits the spherical sample to maximize sensitivity, while also providing excellent RF homogeneity. We further improve NMR sensitivity by employing a spherical shell as the rotor, thereby maximizing sample volume (219 µL in this case of 9.5 mm outer diameter spheres). The spinning gas is supplied by a 3D-printed ring stator external to the coil, thereby introducing a simplified form of MAS stators. In this apparatus, the RF field generated along the coil axis is perpendicular to the external magnetic field, regardless of rotor orientation. We observe a linear increase in sensitivity with increasing sample volume. We also simulate the RF performance of spherical and cylindrical solenoid coils with constant or variable pitch for spherical and cylindrical rotors, respectively. The simulation results show that spherical solenoid coils generate comparable B1 field intensities but have better homogeneity than cylindrical solenoid coils do.

Pentosan polysulfate maculopathy versus age-related macular degeneration: comparative assessment with multimodal imaging.

OBJECTIVE: To evaluate whether pentosan polysulfate maculopathy manifests distinctive imaging features that can be differentiated from those found in age-related macular degeneration (AMD). METHODS: Local databases were queried to identify patients with a diagnosis of interstitial cystitis who were seen at the Emory Eye Center between May 2014 and January 2019 and who had fundus imaging available for review. Ninety patients met the eligibility criteria. Masked graders categorized patients based on imaging characteristics as follows: category 1: pentosan polysulfate maculopathy; category 2: AMD or drusen; category 3: neither; and category 4: unsure. Pentosan polysulfate exposure characteristics were compared among groups. RESULTS: Of the 90 subjects evaluated, 79 (88%) were female and the median age was 61.5 years (range, 30-89). Seventeen patients were placed in category 1; 25 in category 2; 47 in category 3, and; 1 in category 4. Among categories 1 to 4, respectively, 17 (100%), 15 (60%), 28 (60%), and 0 patients had exposure to pentosan polysulfate (p = 0.007). Mean cumulative exposure to pentosan polysulfate across the four categories was 2.1, 0.36, 0.34, and 0 kg, respectively (p < 0.00001). Eyes with pentosan polysulfate maculopathy did not have typical drusen in the macula. CONCLUSION: Although pentosan polysulfate maculopathy resembles some aspects of AMD, the two conditions can be differentiated with the use of multimodal fundus imaging.

Systemic Lupus Erythematosus-associated Retinal Vasculitis Treated with Adalimumab.

PURPOSE: To present a case of refractory systemic lupus erythematosus (SLE)-associated retinal vasculitis that responded to the anti-tumor necrosis factor (TNF)-alpha inhibitor adalimumab as corticosteroid-sparing therapy. METHODS: Descriptive case report of a patient with SLE with retinal vasculitis complicated by an ischemic retinal vein occlusion and cystoid macular edema. RESULTS: A 30-year-old female patient with a history of SLE presented with retinal vasculitis and an ischemic, branch retinal vein occlusion with macular edema in the left eye. Oral corticosteroid was administered along with mycophenolate mofetil (MMF) as a corticosteroid-sparing agent. Despite MMF therapy, the patient developed an exacerbation of her vasculitis with the involvement of both eyes. Adalimumab was initiated with a resultant resolution of retinal vasculitis as a corticosteroid-sparing strategy with over 2 years of follow-up. CONCLUSION: Anti-TNF-alpha therapy with adalimumab may be effective as a corticosteroid-sparing agent in select patients with ocular inflammation associated with SLE.

Biomolecular Perturbations in In-Cell Dynamic Nuclear Polarization Experiments.

In-cell DNP is a growing application of NMR to the study of biomolecular structure and function within intact cells. An important unresolved question for in-cell DNP spectroscopy is the integrity of cellular samples under the cryogenic conditions of DNP. Despite the rich literature around cryopreservation of cells in the fields of stem cell/embryonic cell therapeutics, cell line preservation and in cryo-EM applications, the effect of cryopreservation procedures on DNP parameters is unclear. In this report we investigate cell survival and apoptosis in the presence of cryopreserving agents and DNP radicals. We also assess the effects of these reagents on cellular enhancements. We show that the DNP radical AMUPol has no effect on membrane permeability and does not induce apoptosis. Furthermore, the standard aqueous glass forming reagent, comprised of 60/30/10 d8-glycerol/D2O/H2O (DNP juice), rapidly dehydrates cells and induces apoptosis prior to freezing, reducing structural integrity of the sample prior to DNP analysis. Preservation with d6-DMSO at 10% v/v provided similar DNP enhancements per √unit time compared to glycerol preservation with superior maintenance of cell size and membrane integrity prior to freezing. DMSO preservation also greatly enhanced post-thaw survival of cells slow-frozen at 1°C/min. We therefore demonstrate that in-cell DNP-NMR studies should be done with d6-DMSO as cryoprotectant and raise important considerations for the progression of in-cell DNP-NMR towards the goal of high quality structural studies.

Clinical management of an outbreak of nutritionally variant streptococcus endophthalmitis following intravitreal bevacizumab injection.

BACKGROUND: The management of an outbreak of endophthalmitis associated with intravitreal bevacizumab represents a challenging real-time process involving identification of cases, treatment and mitigation measures during the outbreak. We summarize the clinical presentation and management of a cluster of endophthalmitis cases from contaminated bevacizumab, in addition to mathematical probabilistic assessment of the number of cases that define an outbreak. METHODS: A retrospective study was conducted to assess the management of an endophthalmitis outbreak after intravitreal bevacizumab (IVB) administration. Demographic data, clinical information, individual patient management and public health reporting measures were reviewed. Outcomes of patients who received prophylactic antibiotics for endophthalmitis prevention were also reviewed. Binomial tail probability calculations were performed to determine the likelihood of clusters of endophthalmitis that could inform when an outbreak was evolving that would warrant more public health notification measures and communication. RESULTS: Forty-five eyes of 42 patients who received IVB from a single batch were reviewed. Four cases of endophthalmitis from Granulicatella adiacens, a nutritionally-variant Streptococcus species, were treated successfully with intravitreal antibiotics ± vitrectomy. Thirty-four of the remaining 41 eyes were treated with prophylactic intravitreal vancomycin with no additional cases of endophthalmitis. Outbreak management also included CDC, ASRS and public health authority notification. Binominal tail probabilities demonstrated the rarity of clusters from a single batch (i.e. ~ 1/10,000 for 2 cases; 1/2 million for 3 cases). However, given the U.S. scale of IVB administration, there is an 87% chance of a cluster ≧ 2 and a 1% chance of a cluster ≧ 3 cases annually, which may guide outbreak management. A process diagram was developed to incorporate patient management and public health measures when an outbreak is suspected. CONCLUSION: Intravitreal antibiotics and vitrectomy were effective in the individual management of cases of endophthalmitis, and no serious adverse events occurred with prophylactic intravitreal vancomycin for at-risk eyes. Best practices for outbreaks should be evaluated, given their likelihood within the U.S. and the sight-threatening consequences of endophthalmitis.

Thirteen Years' Progression of Macular Atrophy in a Patient With Jeune Syndrome.

Jeune syndrome is a rare skeletal dysplasia with an associated retinal dystrophy. The authors describe a case of progressive bilateral macular atrophy (with multimodal imaging) in a patient with Jeune syndrome who was followed over 13 years. This case, confirmed with genetic testing, highlights the importance of characterizing the relationship between phenotype and genotype in this genetically heterogenous condition. [Ophthalmic Surg Lasers Imaging Retina. 2021;52:107-109.].

In Situ Detection of Endogenous HIV Activation by Dynamic Nuclear Polarization NMR and Flow Cytometry.

We demonstrate for the first time in-cell dynamic nuclear polarization (DNP) in conjunction with flow cytometry sorting to address the cellular heterogeneity of in-cell samples. Utilizing a green fluorescent protein (GFP) reporter of HIV reactivation, we correlate increased 15N resonance intensity with cytokine-driven HIV reactivation in a human cell line model of HIV latency. As few as 10% GFP+ cells could be detected by DNP nuclear magnetic resonance (NMR). The inclusion of flow cytometric sorting of GFP+ cells prior to analysis by DNP-NMR further boosted signal detection through increased cellular homogeneity with respect to GFP expression. As few as 3.6 million 15N-labeled GFP+ cells could be readily detected with DNP-NMR. Importantly, cell sorting allowed for the comparison of cytokine-treated GFP+ and GFP- cells in a batch-consistent way. This provides an avenue for normalizing NMR spectral contributions from background cellular processes following treatment with cellular modulators. We also demonstrate the remarkable stability of AMUPol (a nitroxide biradical) in Jurkat T cells and achieved in-cell enhancements of 46 with 10 mM AMUPol, providing an excellent model system for further in-cell DNP-NMR studies. This represents an important contribution to improving in-cell methods for the study of endogenously expressed proteins by DNP-NMR.

Pentosan Polysulfate Maculopathy versus Inherited Macular Dystrophies: Comparative Assessment with Multimodal Imaging.

PURPOSE: To evaluate whether pentosan polysulfate (PPS) maculopathy manifests distinctive characteristics that permit differentiation from hereditary maculopathies with multimodal fundus imaging. DESIGN: Retrospective review. PARTICIPANTS: Emory Eye Center databases were queried for the following International Classification of Diseases codes from May 20, 2014, through October 22, 2019: 362.70 (unspecified hereditary retinal dystrophy), 362.74 + H35.52 (pigmentary retinal dystrophy), 362.76 + H35.54 (dystrophies primarily involving the retinal pigment epithelium), and H35.50 (unspecified macular degeneration). METHODS: Fundus images for each patient were evaluated, including color fundus photographs, fundus autofluorescence images, and spectral-domain OCT images. Cases with imaging sufficient for diagnostic classification were analyzed. Masked graders classified patient images as follows: highly suggestive of PPS maculopathy; some features resembling PPS maculopathy, but not classic disease; and clearly distinct from PPS maculopathy. MAIN OUTCOME MEASURES: Sensitivity and specificity for identification of PPS maculopathy by masked reviewers. RESULTS: A total of 1394 patients were evaluated, and 1131 had imaging sufficient for classification. Fifteen patients were categorized as having findings highly suggestive of PPS maculopathy; 25 patients showed some features resembling PPS maculopathy but not classic disease; and 1091 patients showed evidence of disease clearly distinct from PPS maculopathy. All 10 patients with PPS maculopathy in this dataset were correctly categorized as having PPS maculopathy. Five patients without PPS exposure were categorized incorrectly as having PPS maculopathy. This represented a 100% sensitivity and 99.6% specificity for identification of PPS maculopathy by masked review of fundus imaging in this dataset. CONCLUSIONS: The imaging characteristics of PPS maculopathy allow for differentiation from hereditary maculopathies even in the absence of known exposure to the drug.

Characterization of frequency-chirped dynamic nuclear polarization in rotating solids.

Continuous wave (CW) dynamic nuclear polarization (DNP) is used with magic angle spinning (MAS) to enhance the typically poor sensitivity of nuclear magnetic resonance (NMR) by orders of magnitude. In a recent publication we show that further enhancement is obtained by using a frequency-agile gyrotron to chirp incident microwave frequency through the electron resonance frequency during DNP transfer. Here we characterize the effect of chirped MAS DNP by investigating the sweep time, sweep width, center-frequency, and electron Rabi frequency of the chirps. We show the advantages of chirped DNP with a trityl-nitroxide biradical, and a lack of improvement with chirped DNP using AMUPol, a nitroxide biradical. Frequency-chirped DNP on a model system of urea in a cryoprotecting matrix yields an enhancement of 142, 21% greater than that obtained with CW DNP. We then go beyond this model system and apply chirped DNP to intact human cells. In human Jurkat cells, frequency-chirped DNP improves enhancement by 24% over CW DNP. The characterization of the chirped DNP effect reveals instrument limitations on sweep time and sweep width, promising even greater increases in sensitivity with further technology development. These improvements in gyrotron technology, frequency-agile methods, and in-cell applications are expected to play a significant role in the advancement of MAS DNP.

Dynamic Nuclear Polarization with Electron Decoupling in Intact Human Cells and Cell Lysates.

Dynamic nuclear polarization (DNP) is used to improve the inherently poor sensitivity of nuclear magnetic resonance spectroscopy by transferring spin polarization from electrons to nuclei. However, DNP radicals within the sample can have detrimental effects on nuclear spins close to the polarizing agent. Chirped microwave pulses and electron decoupling (eDEC) attenuate these effects in model systems, but this approach is yet to be applied to intact cells or cellular lysates. Herein, we demonstrate for the first time exceptionally fast 1H T1DNP times of just 200 and 300 ms at 90 and 6 K, respectively, using a newly synthesized methylated trityl radical within intact human cells. We further demonstrate that eDEC can also be applied to intact human cells and human and bacterial cell lysates. We investigate eDEC efficiency at different temperatures, with different solvents, and with two trityl radical derivatives. At 90 K, eDEC yields a 13C signal intensity increase of 8% in intact human cells and 10% in human and bacterial cell lysates. At 6 K, eDEC provides larger intensity increases of 15 and 39% in intact human cells and cell lysates, respectively. Combining the manipulation of electron spins with frequency-chirped pulses and sample temperatures approaching absolute zero is a promising avenue for executing rapid, high-sensitivity magic-angle spinning DNP in complex cellular environments.