Identification of a Ubiquinone-Ubiquinol Quinhydrone Complex in Bacterial Photosynthetic Membranes and Isolated Reaction Centers by Time-Resolved Infrared Spectroscopy.

Ubiquinone redox chemistry is of fundamental importance in biochemistry, notably in bioenergetics. The bi-electronic reduction of ubiquinone to ubiquinol has been widely studied, including by Fourier transform infrared (FTIR) difference spectroscopy, in several systems. In this paper, we have recorded static and time-resolved FTIR difference spectra reflecting light-induced ubiquinone reduction to ubiquinol in bacterial photosynthetic membranes and in detergent-isolated photosynthetic bacterial reaction centers. We found compelling evidence that in both systems under strong light illumination-and also in detergent-isolated reaction centers after two saturating flashes-a ubiquinone-ubiquinol charge-transfer quinhydrone complex, characterized by a characteristic band at ~1565 cm-1, can be formed. Quantum chemistry calculations confirmed that such a band is due to formation of a quinhydrone complex. We propose that the formation of such a complex takes place when Q and QH2 are forced, by spatial constraints, to share a common limited space as, for instance, in detergent micelles, or when an incoming quinone from the pool meets, in the channel for quinone/quinol exchange at the QB site, a quinol coming out. This latter situation can take place both in isolated and membrane bound reaction centers Possible consequences of the formation of this charge-transfer complex under physiological conditions are discussed.

Capture of Gaseous Iodine in Isoreticular Zirconium-Based UiO-n Metal-Organic Frameworks: Influence of Amino Functionalization, DFT Calculations, Raman and EPR Spectroscopic Investigation.

A series of Zr-based UiO-n MOF materials (n=66, 67, 68) have been studied for iodine capture. Gaseous iodine adsorption was collected kinetically from a home-made set-up allowing the continuous measurement of iodine content trapped within UiO-n compounds, with organic functionalities (-H, -CH3 , -Cl, -Br, -(OH)2 , -NO2 , -NH2 , (-NH2 )2 , -CH2 NH2 ) by in-situ UV-Vis spectroscopy. This study emphasizes the role of the amino groups attached to the aromatic rings of the ligands connecting the {Zr6 O4 (OH)4 } brick. In particular, the preferential interaction of iodine with lone-pair groups, such as amino functions, has been experimentally observed and is also based on DFT calculations. Indeed, higher iodine contents were systematically measured for amino-functionalized UiO-66 or UiO-67, compared to the pristine material (up to 1211 mg/g for UiO-67-(NH2 )2 ). However, DFT calculations revealed the highest computed interaction energies for alkylamine groups (-CH2 NH2 ) in UiO-67 (-128.5 kJ/mol for the octahedral cavity), and pointed out the influence of this specific functionality compared with that of an aromatic amine. The encapsulation of iodine within the pore system of UiO-n materials and their amino-derivatives has been analyzed by UV-Vis and Raman spectroscopy. We showed that a systematic conversion of molecular iodine (I2 ) species into anionic I- ones, stabilized as I- ⋅⋅⋅I2 or I3 - complexes within the MOF cavities, occurs when I2 @UiO-n samples are left in ambient light.

Grading mitral regurgitation using 4D flow CMR: Comparison to transthoracic echocardiography.

OBJECTIVES: To determine the 4D Flow Cardiac Magnetic Resonance (CMR) thresholds that achieve the best agreement with transthoracic echocardiography (TTE) for grading mitral regurgitation (MR). METHODS: We conducted a single-center prospective study of patients evaluated for chronic primary MR in 2016-2020. MR was evaluated blindly by TTE and 4D Flow CMR, respectively by two cardiologists and two radiologists with decades of experience. MR was graded with both methods as mild, moderate, or severe. 4D Flow CMR measurements included MR regurgitant volume per beat (RV) and mitral anterograde flow per beat (MF). RF was obtained as the ratio RV/MF. Additionally, MF was compared to left ventricular stroke volume (LVSV) by cine-CMR. RESULTS: We included 33 patients in the initial cohort and 33 in the validation cohort. Inter-observer agreement was excellent for 4D Flow CMR ICC = .94 (95% CI, .86-.97, p < 0.0001). Using recommended TTE thresholds (30 ml, 60 ml, 30%, 50%), agreement was moderate for RV and RF. The best agreement between 4D Flow CMR and TTE was obtained with CMR thresholds of 20 and 40 ml for RV (κ = .93; 95% CI, .8-1) and 20% and 37% for RF (κ = .90; 95% CI, .7-.9). In the validation cohort, agreement between TTE and 4D Flow CMR was good with the optimal thresholds (κ = .78; 95% CI, .61-.94). CONCLUSION: We propose CMR thresholds that provide a good agreement between TTE and CMR for grading MR. Further studies are needed to fully validate 4D-Flow CMR accuracy for primary MR quantification.

Characterizing the ZrC(111)/c-ZrO2(111) Hetero-Ceramic Interface: First Principles DFT and Atomistic Thermodynamic Modeling.

The mechanical and physical properties of zirconium carbide (ZrC) are limited to its ability to deteriorate in oxidizing environments. Low refractory oxides are typically formed as layers on ZrC surfaces when exposed to the slightest concentrations of oxygen. However, this carbide has a wide range of applications in nuclear reactor lines and nozzle flaps in the aerospace industry, just to name a few. To develop mechanically strong and oxygen-resistant ZrC materials, the need for studying and characterizing the oxidized layers, with emphasis on the interfacial structure between ZrC and the oxidized phases, cannot be understated. In this paper, the ZrC(111)//c-ZrO2 (111) interface was studied by both finite temperature molecular dynamic simulation and DFT. The interfacial mechanical properties were characterized by the work of adhesion which revealed a Zr|OO|Zr|OO//ZrC(111) interface model as the most stable with an oxygen layer from ZrO2 being deposited on the ZrC(111) surface. Further structural analysis at the interface showed a crack in the first ZrO2 layer at the interfacial region. Investigations of the electronic structure using the density of state calculations and Bader charge analysis revealed the interfacial properties as local effects with no significant impacts in the bulk regions of the interface slab.

Evaluation of atrial septal defects with 4D flow MRI-multilevel and inter-reader reproducibility for quantification of shunt severity.

PURPOSE: With the hypothesis that 4D flow can be used in evaluation of cardiac shunts, we seek to evaluate the multilevel and interreader reproducibility of measurements of the blood flow, shunt fraction and shunt volume in patients with atrial septum defect (ASD) in practice at multiple clinical sites. MATERIALS AND METHODS: Four-dimensional flow MRI examinations were performed at four institutions across Europe and the US. Twenty-nine patients (mean age, 43 years; 11 male) were included in the study. Flow measurements were performed at three levels (valve, main artery and periphery) in both the pulmonary and systemic circulation by two independent readers and compared against stroke volumes from 4D flow anatomic data. Further, the shunt ratio (Qp/Qs) was calculated. Additionally, shunt volume was quantified at the atrial level by tracking the atrial septum. RESULTS: Measurements of the pulmonary blood flow at multiple levels correlate well whether measuring at the valve, main pulmonary artery or branch pulmonary arteries (r = 0.885-0.886). Measurements of the systemic blood flow show excellent correlation, whether measuring at the valve, ascending aorta or sum of flow from the superior vena cava (SVC) and descending aorta (r = 0.974-0.991). Intraclass agreement between the two observers for the flow measurements varies between 0.96 and 0.99. Compared with stroke volume, pulmonic flow is underestimated with 0.26 l/min at the main pulmonary artery level, and systemic flow is overestimated with 0.16 l/min at the ascending aorta level. Direct measurements of ASD flow are feasible in 20 of 29 (69%) patients. CONCLUSION: Blood flow and shunt quantification measured at multiple levels and performed by different readers are reproducible and consistent with 4D flow MRI.

A DFT study of RuO4 interactions with porous materials: metal-organic frameworks (MOFs) and zeolites.

Radioactive gaseous ruthenium tetroxide (RuO4) can be released into the environment in the case of a severe nuclear accident. Using periodic dispersion corrected density functional theory calculations, we have investigated for the first time the adsorption behavior of RuO4 into prototypical porous materials, Metal-Organic Frameworks (MOFs) and zeolites, with the aim of mitigating ruthenium releases to the outside. For the MOFs, we have screened a set of six structures (MIL-53(Al), MIL-120(Al), HKUST-1(Cu), UiO-66(Zr), UiO-67(Zr) and UiO-68(Zr)), while for the zeolites two structures have been selected: mordenite (MOR) with Si/Al ratios of 11 and 5, and faujasite (FAU) with a Si/Al ratio of 2.4. The DFT calculations show that the nature of the porous materials does not have a significant effect on the adsorption energy of RuO4 compounds and that the main interaction is due to the formation of hydrogen bonds. For the tested materials, computational results show that the interaction energies of RuO4 reach their maximum with the hydrated form of HKUST-1(Cu) (-114 kJ mol-1) due to the presence of strong hydrogen bonds between the water molecules and the oxygen atoms of RuO4.

Comparative assessment of image quality for coronary CT angiography with iobitridol and two contrast agents with higher iodine concentrations: iopromide and iomeprol. A multicentre randomized double-blind trial.

OBJECTIVES: To demonstrate non-inferiority of iobitridol 350 for coronary CT angiography (CTA) compared to higher iodine content contrast media regarding rate of patients evaluable for the presence of coronary artery stenoses. METHODS: In this multicentre trial, 452 patients were randomized to receive iobitridol 350, iopromide 370 or iomeprol 400 and underwent coronary CTA using CT systems with 64-detector rows or more. Two core lab readers assessed 18 coronary segments per patient regarding image quality (score 0 = non diagnostic to 4 = excellent quality), vascular attenuation, signal and contrast to noise ratio (SNR, CNR). Patients were considered evaluable if no segment had a score of 0. RESULTS: Per-patient, the rate of fully evaluable CT scans was 92.1, 95.4 and 94.6 % for iobitridol, iopromide and iomeprol, respectively. Non-inferiority of iobitridol over the best comparator was demonstrated with a 95 % CI of the difference of [-8.8 to 2.1], with a pre-specified non-inferiority margin of -10 %. Although average attenuation increased with higher iodine concentrations, average SNR and CNR did not differ between groups. CONCLUSIONS: With current CT technology, iobitridol 350 mg iodine/ml is not inferior to contrast media with higher iodine concentrations in terms of image quality for coronary stenosis assessment. KEY POINTS: • Iodine concentration is an important parameter for image quality in coronary CTA. • Contrast enhancement must be balanced against the amount of iodine injected. • Iobitridol 350 is non-inferior compared to CM with higher iodine concentrations. • Higher attenuation with higher iodine concentrations, but no SNR or CNR differences.

Dissociative iodomethane adsorption on Ag-MOR and the formation of AgI clusters: an ab initio molecular dynamics study.

Radioactive iodine species belong to the most dangerous components of nuclear effluents and waste produced by nuclear facilities. In this work, we use computer simulations at the periodic DFT level to investigate dissociative adsorption of iodomethane on silver-exchanged mordenite, which is among the most effective sorbents of iodine species available today. The structure, energetics, and mobility of complexes Ag-(CH3I) and Ag-(CH3I)2 formed upon adsorption of iodomethane on Ag+ sites are investigated using the ab initio MD approach. The free-energy profiles for the reaction CH3I + Ag-MOR → AgI + CH3-MOR are determined using the blue moon ensemble technique. The AgI species formed as a product of dissociative adsorption are shown to combine spontaneously into small clusters (AgI)n with the dimensions restricted by the size and geometry of confining voids. The structure and energetics of the (AgI)n species are analysed in detail and compared with the available experimental and theoretical data. The internal energy of formation of clusters in mordenite is shown to contribute significantly to the shift of equilibrium from the undissociated to dissociated form of adsorbed CH3I.

Dynamics of a plasmon-activated p-mercaptobenzoic acid layer deposited over Au nanoparticles using time-resolved SERS.

Time-dependent SERS intensity recorded over a drop-coated coffee-ring pattern of p-MBA with gold colloids was investigated as a function of the specific laser power applied. Pure electromagnetic enhancement produced stochastic intensity variations of the whole SER spectra, which were mainly correlated with evolutions of the background intensity. Besides long-term, non-reversible spectral changes caused by plasmon-induced decarboxylation of p-MBA, transient original spectral profiles showing additional lines were also observed as the specific power reached 5.5 × 10(4) W cm(-2). An unprecedented qualitative and quantitative study of SERS intensity variations based on the complementary use of both extreme deviation and cross-correlation statistics is provided, which resulted in an improved understanding of SERS mechanisms. More precisely, cross-correlation analysis made it possible to follow the evolution of groups of modes assigned to one species or sharing the same symmetry while so-called individual events denote particular resonance structures, whose occurrence was tentatively related to a photo-thermally activated motion of the gold nanostructures.

Energetics of CO oxidation on lanthanide-free perovskite systems: the case of Co-doped SrTiO3.

The energetics of the catalytic oxidation of CO on a complex metal oxide are investigated for the first time via density functional theory calculations. The catalyst, Co-doped SrTiO3, is modelled using periodically repeated slabs based on the SrTiO3(100) surface. The comparison of the energy profiles obtained for the pure host and the Co-doped material reveals the actual pathway followed by the reaction, and shows that Co doping enhances the catalytic properties of SrTiO3 by reducing the energy cost for the formation of oxygen vacancies.

Diagnosis of functionally significant coronary stenosis with exercise CT myocardial perfusion imaging.

PURPOSE: To assess the feasibility of exercise perfusion computed tomography (CT) in patients suspected of having hemodynamically significant coronary stenosis. MATERIALS AND METHODS: This study had institutional review board approval, and all patients gave informed consent. Thirty-two consecutive patients (26 men [mean age, 63 years] and six women [mean age, 71 years]) with 55 coronary stenoses of at least 50% underwent coronary CT angiography (one stenosis in 13 patients, two stenoses in 15 patients, and three stenoses in four patients). CT myocardial perfusion imaging was performed within 1 minute after patients performed supine exercise on an ergometer secured to the CT table. The pressure-rate product was computed to assess level of exercise. The myocardial enhancement ratio between stenotic and normally perfused territories was determined for each stenosis. Fractional flow reserve less than 0.8, as measured during invasive coronary angiography, was the reference for defining significant stenoses. Receiver operating characteristic curves were constructed to determine the myocardial enhancement ratio cutoff value. RESULTS: In the per-patient analysis, a myocardial enhancement ratio cutoff of 0.8 performed best for identifying functionally significant stenosis: Sensitivity was 95% (21 of 22 patients), specificity was 90% (nine of 10 patients), positive predictive value was 95% (21 of 22 patients), negative predictive value was 90% (nine of 10 patients), and accuracy was 94% (30 of 32 patients). Corresponding values in the per-stenosis analysis were 97% (29 of 30 stenoses), 96% (23 of 24 stenoses), 97% (29 of 30 stenoses), 96% (23 of 24 stenoses), and 96% (52 of 54 stenoses), respectively. CONCLUSION: Exercise CT myocardial perfusion imaging is feasible and accurate for assessment of the functional significance of coronary stenosis.

Anatomical criteria of malignancy by computed tomography angiography in patients with anomalous coronary arteries with an interarterial course.

PURPOSE: We sought to determine the relation between major adverse cardiac events (MACE) and anatomical criteria assessed by coronary computed tomography angiography (CCTA) in patients with an anomalous coronary artery with an interarterial course (ACAIAC). MATERIAL AND METHODS: We selected CCTA studies of patients with an ACAIAC from a database of 4,160 examinations and studied anatomical criteria according to the presence of prior MACE, defined as syncope, unstable angina, myocardial infarction and resuscitated sudden cardiac death. RESULTS: There were 19 patients (18 males) with an ACAIAC during the study period (incidence 0.46 %). Seven patients with prior MACE were younger (26 years vs 59 years, p < 0.001), had a smaller minimal lumen area (3.6 mm(2) vs 9.0 mm(2), p = 0.001), a higher degree of area stenosis (57 % vs 24 %, p = 0.001), a longer interarterial course (14.7 vs 8.6 mm, p = 0.003) and a smaller proximal segment width (1.6 mm vs 2.5 mm, p = 0.02) compared with the 12 patients without prior MACE. All patients with MACE had the following concomitant anatomical characteristics: minimum lumen area ≤4 mm(2), an area stenosis ≥50 % and intra-arterial length >10 mm CONCLUSIONS: Prior MACE is associated with specific anatomical CCTA characteristics among patients with ACAIAC. CCTA may therefore contribute to distinguish patients at risk of adverse events.

Stability, equilibrium morphology and hydration of ZrC(111) and (110) surfaces with H2O: a combined periodic DFT and atomistic thermodynamic study.

ZrC is a non-oxide ultra-high temperature ceramic (UHTC) material with excellent physical and mechanical properties used in nuclear plants and jet propulsion engines. However, the mechanical properties can be lost because of the easy oxidation of its grain surfaces. One way of dealing with such a problem is to coat the surface with inert carbides like SiC which can be grafted onto the ZrC surface by first modifying the exposed surfaces with reactive molecules. The stability of different terminations of the (111) facet was studied and the most stable is the termination on both surface layers by Zr atoms as it has been observed experimentally. A DFT calculation study jointly with atomistic thermodynamic modelling has been used to study the reactivity of the (111) and (110) facets with H2O. H2O dissociates into surface hydroxyl groups with the release of H2 and the OH groups preferentially adsorb at high surface coverage (high adsorption energies at 1 ML coverage). The study of adsorption of H2O onto other low index surfaces allows the determination of the equilibrium morphology of the ZrC nanocrystallites in different environments. In vacuum, ZrC nanocrystallites reveal a cubic structure with much of the (100) surface and a small amount of the (111) facets at the corners. Hydration of the (111) surface was a strong process and hence water can be removed from the surface at temperatures above 1200 K and pressures lower than 10(-9) bar while higher pressures of H2 in the gas phase enhance the removal of water. The Wulff construction of the nanocrystallites after hydration indicates only the (111) surface at lower temperatures while revealing the (100) facets at higher temperatures. Thus whatever the experimental conditions be, the (110) facet does not have to be considered.

Microvascular disease in chronic thromboembolic pulmonary hypertension: a role for pulmonary veins and systemic vasculature.

Limited numbers of operated patients with chronic thromboembolic pulmonary hypertension (CTEPH) are refractory to pulmonary endarterectomy (PEA) and experience persistent pulmonary hypertension (PH). We retrospectively assessed lung histology available from nine patients with persistent PH (ineffective PEA (inPEA) group) and from eight patients transplanted for distal CTEPH inaccessible by PEA (noPEA group). Microscopically observed peculiarities were compared with the histology of a recently developed CTEPH model in piglets. Pre-interventional clinical/haemodynamic data and medical history of patients from the inPEA and noPEA groups were collected and analysed. Conspicuous remodelling of small pulmonary arteries/arterioles, septal veins and pre-septal venules, including focal capillary haemangiomatosis, as well as pronounced hypertrophy and enlargement of bronchial systemic vessels, were the predominant pattern in histology from both groups. Most findings were reproduced in our porcine CTEPH model. Ink injection experiments unmasked abundant venular involvement in so-called small vessel or microvascular disease, as well as post-capillary bronchopulmonary shunting in human and experimental CTEPH. Microvascular disease is partly due to post-capillary remodelling in human and experimental CTEPH and appears to be related to bronchial-to-pulmonary venous shunting. Further studies are needed to clinically assess the functional importance of this finding.