Water Promotes Melting of a Metal-Organic Framework.

Water is one of the most reactive and abundant molecules on Earth, and it is thus crucial to understand its reactivity with various material families. One of the big unknown questions is how water in liquid and vapor forms impact the fast-emerging class of metal-organic frameworks (MOFs). Here, we discover that high-pressure water vapor drastically modifies the structure and hence the dynamic, thermodynamic, and mechanical properties of MOF glasses. In detail, we find that an archetypical MOF (ZIF-62) is extremely sensitive to heat treatments performed at 460 °C and water vapor pressures up to ∼110 bar. Both the melting and glass transition temperatures decrease remarkably (by >100 °C), and simultaneously, hardness and Young's modulus increase by up to 100% under very mild treatment conditions (<20 bar of hydrothermal pressure). Structural analyses suggest water to partially coordinate to Zn in the form of a hydroxide ion by replacing a bridging imidazolate-based linker. The work provides insight into the role of hot-compressed water in influencing the structure and properties of MOF glasses and opens a new route for systematically changing the thermodynamics and kinetics of MOF liquids and thus altering the thermal and mechanical properties of the resulting MOF glasses.

Intersession reliability of lower limb muscle strength assessments in adults with obesity eligible for bariatric surgery.

BACKGROUND: The aim of this study was to examine the test-retest reliability in lower limb muscle strength and rate of torque development (RTD) using isokinetic dynamometry in adults with obesity, with a body mass index (BMI) ≥ 35 kg/m2 . METHOD: Thirty-two adults with a BMI of 43.8 ± 6.6 kg/m2 eligible for bariatric surgery were enroled in the study. Isokinetic and isometric knee extensor (KE) and flexor (KF) strength were assessed in an isokinetic dynamometer (Biodex 4) during three test sessions separated by 3-7 days. RESULTS: There were no statistical differences in peak KE and KF torque for any test modalities between sessions. Intraclass correlation (ICC) was 0.91-0.94 between sessions 1 and 2 and 0.94-0.97 between sessions 2 and 3. Standard error of measurement (SEM%) and coefficient of variation (CV) ranged across test sessions from 4.3% to 7.3%. KE RTD showed high test-retest reliability following familiarization, with ICC, CV and SEM% values ranging from 0.84 to 0.90, 13.3%-20.3% and 14.6%-24.9%, respectively. CONCLUSION: Maximal lower limb muscle strength measured by isokinetic dynamometry showed excellent test-retest reliability manifested by small measurement errors and low CV. Reliability was slightly improved by including a familiarization session. KE RTD but not KF RTD demonstrated high test-retest reliability following familiarization. The present data indicate that isokinetic dynamometry can be used to detect even small changes in lower limb muscle strength in adults with obesity.

Anesthesiologists' skills in emergency cricothyroidotomy mandate a brush-up training after 3 months-A randomized controlled trial.

BACKGROUND: In the Difficult Airway Society's 2015 "cannot intubate, cannot oxygenate" guideline, the emergency cricothyroidotomy is the final option when managing an unanticipated difficult airway. How often training for maintenance of this skill is required for anesthesiologists remains unknown. We aimed to assess if specialist-trained anesthesiologists' skills improved from a brush-up intervention and if skills were retained after 3 months. METHODS: In this multicenter, randomized, controlled trial, participants were randomized to either a simulation-based brush-up or no brush-up. Both groups performed a mannequin-based technical skills emergency cricothyroidotomy test twice and were assessed by a blinded rater using a structured assessment tool that included time, positioning, palpation, appropriate employment of instruments, and stepwise progression. After 3 months of non-training, participants completed identical tests of retention. RESULTS: A total of 54 anesthesiologists were included from three hospitals in the Region of Southern Denmark. Thirty-seven percent of the participants had received skills training in emergency cricothyroidotomy in the prior 12 months. The intervention group (N = 27) performed better in the initial tests, with a mean time of 51.5 s (SD = 10.82), a total score per minute of 15.9 points (SD = 4.91), and 93% passing both initial tests compared to the control group (N = 27) with a mean time of 76.8 s (SD = 35.82), a total score per minute of 6.6 (SD = 4.68) and only 15% passing both initial tests. The intervention group managed to retain overall performance in retention tests in terms of performance time (48.9 s, p = .26), total score per minute (13.6 points, p = .094), and passing the tests (75%, p = .059). CONCLUSION: Exposure to simulation-based brush-up training in emergency cricothyroidotomy improved anesthesiologists' technical performance and was overall retained after 3 months. Some loss of skill concerning specific items was observed, highlighting the need for regular training in emergency cricothyroidotomy. Simulation-based training should be prioritized to improve and maintain technical skills in infrequent high-stakes procedures.

Education in Focused Assessment With Sonography for Trauma Using Immersive Virtual Reality: A Prospective, Interventional Cohort Study and Non-inferiority Analysis With a Historical Control.

OBJECTIVE: Focused assessment with sonography for trauma (FAST) is a valuable ultrasound procedure in emergency settings, and there is a need for evidence-based education in FAST to ensure competencies. Immersive virtual reality (IVR) is a progressive training modality gaining traction in the field of ultrasound training. IVR holds several economic and practical advantages to the common instructor-led FAST courses using screen-based simulation (SBS). METHODS: This prospective, interventional cohort study investigated whether training FAST using IVR unsupervised and out-of-hospital was non-inferior to a historical control group training at a 90 min SBS course in terms of developing FAST competencies in novices. Competencies were assessed in both groups using the same post-training simulation-based FAST test with validity evidence, and a non-inferiority margin of 2 points was chosen. RESULTS: A total of 27 medical students attended the IVR course, and 27 junior doctors attended the SBS course. The IVR group trained for a median time of 117 min and scored a mean 14.2 ± 2.0 points, compared with a mean 13.7 ± 2.5 points in the SBS group. As the lower bound of the 95% confidence interval at 13.6 was within the range of the non-inferiority margin (11.7-13.7 points), training FAST in IVR for a median of 117 min was found non-inferior to training at a 90 min SBS course. No significant correlation was found between time spent in IVR and test scores. CONCLUSION: Within the limitations of the use of a historical control group, the results suggest that IVR could be an alternative to SBS FAST training and suitable for unsupervised, out-of-hospital courses in basic FAST competencies.

Education in Focused Lung Ultrasound Using Gamified Immersive Virtual Reality: A Randomized Controlled Study.

Focused lung ultrasound (FLUS) has high diagnostic accuracy in many common conditions seen in a variety of emergency settings. Competencies are essential for diagnostic success and patient safety but can be challenging to acquire in clinical environments. Immersive virtual reality (IVR) offers an interactive risk-free learning environment and is progressing as an educational tool. First, this study explored the educational impact of novice FLUS users participating in a gamified or non-gamified IVR training module in FLUS by comparing test scores using a test with proven validity evidence. Second, the learning effect was assessed by comparing scores of each group with known test scores of novices, intermediates and experienced users in FLUS. A total of 48 participants were included: 24 received gamified and 24 received non-gamified IVR training. No significant difference was found between gamified (mean = 15.5 points) and non-gamified (mean = 15.2 points), indicating that chosen gamification elements for our setup did not affect learning outcome (p = 0.66). The mean scores of both groups did not significantly differ from those of known intermediate users in FLUS (gamified p = 0.63, non-gamified p = 0.24), indicating that both IVR modules could be used as unsupervised out-of-hospital training for novice trainees in FLUS.

Can virtual-reality simulation ensure transthoracic echocardiography skills before trainees examine patients?

Objectives: This study aimed to develop and gather the validity evidence for a standardised simulation-based skills test in transthoracic echocardiography and to establish a credible pass/fail score. Methods: Experts developed a virtual-reality simulator test in cardiology, medical education and simulation-based education. Thirty-six physicians with different experiences in transthoracic echocardiography completed the test at Odense University Hospital, Denmark. The performances of novice, intermediate and experienced participants were compared using the Bonferroni post hoc test. Cronbach's alpha was used to determine the internal consistency reliability of the test. The consistency of performance was analysed using the intraclass correlation coefficient. A pass/fail score was established using the contrasting groups' standard-setting method. Results: We developed a test with high consistent reliability (Alpha = .81), 95% CI [.69, .89]. In both cases, the performers' level was consistent, fitting others at the same level of experience (intraclass correlation r(35)=.81, p<.001). A pass/fail score of 48/50 points was established based on the mean test score of novice and experienced physicians. Conclusions: We developed a standardised virtual-reality simulation-based test of echocardiography skills with the ability to distinguish between participants with different levels of transthoracic echocardiography experience. This test could direct a mastery learning training program where trainees practise until they reach the pre-defined level and secure a higher level of competency to ensure quality and safety for patients.

Single-spin vector analysis of strongly coupled nuclei in TOCSY NMR experiments.

This paper presents a new way to represent the effect of complex radio-frequency (rf) pulse sequences on J-coupled nuclear spin systems. The model uses a vector representation of the single-spin interactions (chemical-shift and rf interactions) and provides a simple route to gain analytical insight into multipulse NMR experiments. The single-spin Hamiltonian is expressed in an interaction representation as Fourier components. These Fourier components are combined for the two spins to establish the averaged coupling term of the Hamiltonian. This effective Hamiltonian is fast to calculate as only single-spin rotations are used and followed by simple summation of numbers for reconstruction of given coupling interactions. The present method is used to gain analytical insight into the performance of the J-coupling transfer sequence DIPSI-2 through two figures of merit (FOM) providing useful information for optimization of such pulse sequences. The first FOM (ΞAB) reports the efficiency of the desired total correlation spectroscopy transfer and should be as large as possible, while the second (ΞHet) reports the potential leakage of coherence to a heteronuclear spin and should be as small as possible.

A general theoretical description of the influence of isotropic chemical shift in dipolar recoupling experiments for solid-state NMR.

We present a general theoretical description that allows us to describe the influence of isotropic chemical shift in homonuclear and heteronuclear dipolar recoupling experiments in magic-angle-spinning solid-state NMR. Through a transformation of the Hamiltonian into an interaction frame with the combined radio-frequency irradiation and the isotropic chemical shift, we determine an effective Hamiltonian to first order with respect to the relevant internal nuclear spin interactions. This unravels the essential resonance conditions for efficient dipolar recoupling. Furthermore, we propose how to handle situations where the resonance conditions are not exactly fulfilled. To verify the general theoretical description, we compare numerical simulations using a time-sliced time-dependent Hamiltonian with simulations using the calculated effective Hamiltonian for propagation. The comparisons are exemplified for the homonuclear dipolar recoupling experiments C721 and POST-C721.

Handling the influence of chemical shift in amplitude-modulated heteronuclear dipolar recoupling solid-state NMR.

We present a theoretical analysis of the influence of chemical shifts on amplitude-modulated heteronuclear dipolar recoupling experiments in solid-state NMR spectroscopy. The method is demonstrated using the Rotor Echo Short Pulse IRrAdiaTION mediated Cross-Polarization ((RESPIRATION)CP) experiment as an example. By going into the pulse sequence rf interaction frame and employing a quintuple-mode operator-based Floquet approach, we describe how chemical shift offset and anisotropic chemical shift affect the efficiency of heteronuclear polarization transfer. In this description, it becomes transparent that the main attribute leading to non-ideal performance is a fictitious field along the rf field axis, which is generated from second-order cross terms arising mainly between chemical shift tensors and themselves. This insight is useful for the development of improved recoupling experiments. We discuss the validity of this approach and present quaternion calculations to determine the effective resonance conditions in a combined rf field and chemical shift offset interaction frame transformation. Based on this, we derive a broad-banded version of the (RESPIRATION)CP experiment. The new sequence is experimentally verified using SNNFGAILSS amyloid fibrils where simultaneous (15)N → (13)CO and (15)N → (13)Cα coherence transfer is demonstrated on high-field NMR instrumentation, requiring great offset stability.

Improved transfer efficiencies in radio-frequency-driven recoupling solid-state NMR by adiabatic sweep through the dipolar recoupling condition.

The homonuclear radio-frequency driven recoupling (RFDR) experiment is commonly used in solid-state NMR spectroscopy to gain insight into the structure of biological samples due to its ease of implementation, stability towards fluctuations/missetting of radio-frequency (rf) field strength, and in general low rf requirements. A theoretical operator-based Floquet description is presented to appreciate the effect of having a temporal displacement of the π-pulses in the RFDR experiment. From this description, we demonstrate improved transfer efficiency for the RFDR experiment by generating an adiabatic passage through the zero-quantum recoupling condition. We have compared the performances of RFDR and the improved sequence to mediate efficient (13)CO to (13)Cα polarization transfer for uniformly (13)C,(15)N-labeled glycine and for the fibril forming peptide SNNFGAILSS (one-letter amino acid codes) uniformly (13)C,(15)N-labeled at the FGAIL residues. Using numerically optimized sweeps, we get experimental gains of approximately 20% for glycine where numerical simulations predict an improvement of 25% relative to the standard implementation. For the fibril forming peptide, using the same sweep parameters as found for glycine, we have gains in the order of 10%-20% depending on the spectral regions of interest.

Low-power polarization transfer between deuterons and spin-1/2 nuclei using adiabatic (RESPIRATION)CP in solid-state NMR.

Establishing high-resolution structures of biological macromolecules in heterogeneous environments by MAS solid-state NMR is an important challenge where development of advanced experimental procedures is in high demand. Promising new methods take advantage of samples with extensive (2)H, (13)C, and (15)N isotope labelling, effectively diluting (1)H spins. In many cases, a sufficient amount of (1)H at exchangeable sites cannot be re-established during the purification procedure, hence it is necessary to exploit also the potential of (2)H as a starting point in pulse sequences, capitalizing on its short T1 as compared to (13)C, and to detect carbon or proton spins as appropriate. Here we present a new method that enables the required high-efficiency (2)H to (13)C or (15)N polarization transfer to be accomplished under the limited (2)H rf power conditions using current (1)H, (2)H, (13)C and (15)N quadruple-resonance MAS NMR instrumentation.

Broad-Band DREAM Recoupling Sequence.

We describe a more broad-banded version of the DREAM double-quantum dipolar-recoupling sequence, which is devised by superimposing a phase-alternating RF irradiation scheme, that is, XiX pulses, on top of the original DREAM sequence. We call this sequence XiX(CW) DREAM. The recoupling conditions and the corresponding first-order effective Hamiltonian are analyzed using triple-mode Floquet theory. The performance of the XiX(CW) DREAM sequence is compared to the original DREAM sequence by numerical simulations and experiments on small model substances and the model protein ubiquitin. The results confirm that XiX(CW) DREAM shows a wider recoupling bandwidth compared to that of DREAM, therefore making the choice for the position of the carrier frequency less critical.

Solid-state NMR sequential assignments of the amyloid core of full-length Sup35p.

Sup35p is a yeast prion and is responsible for the [PSI(+)] trait in Saccharomyces cerevisiae. With 685 amino acids, full-length soluble and fibrillar Sup35p are challenging targets for structural biology as they cannot be investigated by X-ray crystallography or NMR in solution. We present solid-state NMR studies of fibrils formed by the full-length Sup35 protein. We detect an ordered and rigid core of the protein that gives rise to narrow and strong peaks, while large parts of the protein show either static disorder or dynamics on time scales which interfere with dipolar polarization transfer or shorten the coherence lifetime. Thus, only a small subset of resonances is observed in 3D spectra. Here we describe in detail the sequential assignments of the 22 residues for which resonances are observed in 3D spectra: their chemical shifts mostly corresponding to ß-sheet secondary structure. We suspect that these residues form the amyloid core of the fibril.

Adiabatic Rotor-Echo-Short-Pulse-Irradiation mediated cross-polarization.

We present a new dipolar recoupling method for efficient and robust heteronuclear polarization transfer in solid-state NMR under magic-angle-spinning (MAS) conditions. The method combines the recent (RESPIRATION)CP method with a modulation of the amplitude of the rotor-synchronized pulses at one of the involved rf channels through the recoupling condition. In this manner, it is possible to achieve high transfer efficiencies while maintaining robustness towards rf-field inhomogeneities and resonance offsets. The performance of the so-called adiabatic-(RESPIRATION)CP experiment is demonstrated numerically and experimentally using uniformly (13)C,(15)N-labeled samples of alanine and ubiquitin. In particular for cases with relatively high rf inhomogeneity, the scheme offers advantages over the commonly used dipolar recoupling pulse sequences.

Genome-wide profiling identifies a DNA methylation signature that associates with TET2 mutations in diffuse large B-cell lymphoma.

The discovery that the Ten-Eleven Translocation (TET) hydroxylases cause DNA demethylation has fundamentally changed the notion of how DNA methylation is regulated. Clonal analysis of the hematopoetic stem cell compartment suggests that TET2 mutations can be early events in hematologic cancers and recent investigations have shown TET2 mutations in diffuse large B-cell lymphoma. However, the detection rates and the types of TET2 mutations vary, and the relation to global methylation patterns has not been investigated. Here, we show TET2 mutations in 12 of 100 diffuse large B-cell lymphomas with 7% carrying loss-of-function and 5% carrying missense mutations. Genome-wide methylation profiling using 450K Illumina arrays identified 315 differentially methylated genes between TET2 mutated and TET2 wild-type cases. TET2 mutations are primarily associated with hypermethylation within CpG islands (70%; P<0.0001), and at CpG-rich promoters (60%; P<0.0001) of genes involved in hematopoietic differentiation and cellular development. Hypermethylated loci in TET2 mutated samples overlap with the bivalent (H3K27me3/H3K4me3) silencing mark in human embryonic stem cells (P=1.5×10(-30)). Surprisingly, gene expression profiling showed that only 11% of the hypermethylated genes were down-regulated, among which there were several genes previously suggested to be tumor suppressors. A meta-analysis suggested that the 35 hypermethylated and down-regulated genes are associated with the activated B-cell-like type of diffuse large B-cell lymphoma in other studies. In conclusion, our data suggest that TET2 mutations may cause aberrant methylation mainly of genes involved in hematopoietic development, which are silenced but poised for activation in human embryonic stem cells.

Refocused continuous-wave decoupling: a new approach to heteronuclear dipolar decoupling in solid-state NMR spectroscopy.

A novel strategy for heteronuclear dipolar decoupling in magic-angle spinning solid-state nuclear magnetic resonance (NMR) spectroscopy is presented, which eliminates residual static high-order terms in the effective Hamiltonian originating from interactions between oscillating dipolar and anisotropic shielding tensors. The method, called refocused continuous-wave (rCW) decoupling, is systematically established by interleaving continuous wave decoupling with appropriately inserted rotor-synchronized high-power π refocusing pulses of alternating phases. The effect of the refocusing pulses in eliminating residual effects from dipolar coupling in heteronuclear spin systems is rationalized by effective Hamiltonian calculations to third order. In some variants the π pulse refocusing is supplemented by insertion of rotor-synchronized π/2 purging pulses to further reduce the residual dipolar coupling effects. Five different rCW decoupling sequences are presented and their performance is compared to state-of-the-art decoupling methods. The rCW decoupling sequences benefit from extreme broadbandedness, tolerance towards rf inhomogeneity, and improved potential for decoupling at relatively low average rf field strengths. In numerical simulations, the rCW schemes clearly reveal superior characteristics relative to the best decoupling schemes presented so far, which we to some extent also are capable of demonstrating experimentally. A major advantage of the rCW decoupling methods is that they are easy to set up and optimize experimentally.

Simultaneous acquisition of PAR and PAIN spectra.

We present a scheme that allows the simultaneous detection of PAR and PAIN correlation spectra in a single two-dimensional experiment. For both spectra, we obtain almost the same signal-to-noise ratio as if a PAR or PAIN spectrum is recorded separately, which in turn implies that one of the spectra may be considered additional information for free. The experiment is based on the observation that in a PAIN experiment, the PAR condition is always also fulfilled. The performance is demonstrated experimentally using uniformly (13)C,(15)N-labeled samples of N-f-MLF-OH and ubiquitin.

Dipolar recoupling.

We describe the principles and applications of dipolar recoupling in solid-state NMR spectroscopy as a means to access information about molecular structure and transfer magnetization between spins. In this manner, dipolar recoupling forms an essential basis for multiple-dimensional solid-state NMR experiments from which information about structure and dynamics can be extracted. We introduce the basic formalism needed to understand such experiments, present some powerful design principles, and on this basis describe in a coherent way a series of homo- and heteronuclear dipolar recoupling experiments. These experiments serve to highlight design strategies, the gradual development of increasingly advanced and powerful methods, and reflect the application of dipolar recoupling in biological solid-state NMR spectroscopy.

Broadband Heteronuclear Solid-State NMR Experiments by Exponentially Modulated Dipolar Recoupling without Decoupling.

We present a novel solid-state NMR method for heteronuclear dipolar recoupling without decoupling. The method, which introduces the concept of exponentially modulated rf fields, provides efficient broadband recoupling with large flexibility with respect to hetero- or homonuclear applications, sample spinning frequency, and operation without the need for high-power (1)H decoupling. For previous methods, the latter has been a severe source of sample heating which may cause detoriation of costly samples. The so-called EXPonentially mOdulated Recoupling Technique (EXPORT) is described analytically and numerically, and demonstrated experimentally by 1D (13)C spectra and 2D (13)C-(15)N correlation spectra of (13)C,(15)N-labeled samples of GB1, ubiquitin, and fibrils of the SNNFGAILSS fragment of amylin. Through its flexible operation, robustness, and strong performance, it is anticipated that EXPORT will find immediate application for both hetero- and homonuclear dipolar recoupling in solid-state NMR of (13)C,(15)N-labeled proteins and compounds of relevance in chemistry.