Atlas of clinically distinct cell states and ecosystems across human solid tumors.

Determining how cells vary with their local signaling environment and organize into distinct cellular communities is critical for understanding processes as diverse as development, aging, and cancer. Here we introduce EcoTyper, a machine learning framework for large-scale identification and validation of cell states and multicellular communities from bulk, single-cell, and spatially resolved gene expression data. When applied to 12 major cell lineages across 16 types of human carcinoma, EcoTyper identified 69 transcriptionally defined cell states. Most states were specific to neoplastic tissue, ubiquitous across tumor types, and significantly prognostic. By analyzing cell-state co-occurrence patterns, we discovered ten clinically distinct multicellular communities with unexpectedly strong conservation, including three with myeloid and stromal elements linked to adverse survival, one enriched in normal tissue, and two associated with early cancer development. This study elucidates fundamental units of cellular organization in human carcinoma and provides a framework for large-scale profiling of cellular ecosystems in any tissue.

Comprehensive Molecular Characterization of Muscle-Invasive Bladder Cancer.

We report a comprehensive analysis of 412 muscle-invasive bladder cancers characterized by multiple TCGA analytical platforms. Fifty-eight genes were significantly mutated, and the overall mutational load was associated with APOBEC-signature mutagenesis. Clustering by mutation signature identified a high-mutation subset with 75% 5-year survival. mRNA expression clustering refined prior clustering analyses and identified a poor-survival "neuronal" subtype in which the majority of tumors lacked small cell or neuroendocrine histology. Clustering by mRNA, long non-coding RNA (lncRNA), and miRNA expression converged to identify subsets with differential epithelial-mesenchymal transition status, carcinoma in situ scores, histologic features, and survival. Our analyses identified 5 expression subtypes that may stratify response to different treatments.

Reversible, Specific, Active Aggregates of Endogenous Proteins Assemble upon Heat Stress.

Heat causes protein misfolding and aggregation and, in eukaryotic cells, triggers aggregation of proteins and RNA into stress granules. We have carried out extensive proteomic studies to quantify heat-triggered aggregation and subsequent disaggregation in budding yeast, identifying >170 endogenous proteins aggregating within minutes of heat shock in multiple subcellular compartments. We demonstrate that these aggregated proteins are not misfolded and destined for degradation. Stable-isotope labeling reveals that even severely aggregated endogenous proteins are disaggregated without degradation during recovery from shock, contrasting with the rapid degradation observed for many exogenous thermolabile proteins. Although aggregation likely inactivates many cellular proteins, in the case of a heterotrimeric aminoacyl-tRNA synthetase complex, the aggregated proteins remain active with unaltered fidelity. We propose that most heat-induced aggregation of mature proteins reflects the operation of an adaptive, autoregulatory process of functionally significant aggregate assembly and disassembly that aids cellular adaptation to thermal stress.

Interaction of high-fat diet and brain trauma alters adipose tissue macrophages and brain microglia associated with exacerbated cognitive dysfunction.

Obesity increases the morbidity and mortality of traumatic brain injury (TBI). Detailed analyses of transcriptomic changes in the brain and adipose tissue were performed to elucidate the interactive effects between high-fat diet-induced obesity (DIO) and TBI. Adult male mice were fed a high-fat diet (HFD) for 12 weeks prior to experimental TBI and continuing after injury. High-throughput transcriptomic analysis using Nanostring panels of the total visceral adipose tissue (VAT) and cellular components in the brain, followed by unsupervised clustering, principal component analysis, and IPA pathway analysis were used to determine shifts in gene expression patterns and molecular pathway activity. Cellular populations in the cortex and hippocampus, as well as in VAT, during the chronic phase after combined TBI-HFD showed amplification of central and peripheral microglia/macrophage responses, including superadditive changes in selected gene expression signatures and pathways. Furthermore, combined TBI and HFD caused additive dysfunction in Y-Maze, Novel Object Recognition (NOR), and Morris water maze (MWM) cognitive function tests. These novel data suggest that HFD-induced obesity and TBI can independently prime and support the development of altered states in brain microglia and VAT, including the disease-associated microglia/macrophage (DAM) phenotype observed in neurodegenerative disorders. The interaction between HFD and TBI promotes a shift toward chronic reactive microglia/macrophage transcriptomic signatures and associated pro-inflammatory disease-altered states that may, in part, underlie the exacerbation of cognitive deficits. Thus, targeting of HFD-induced reactive cellular phenotypes, including in peripheral adipose tissue immune cell populations, may serve to reduce microglial maladaptive states after TBI, attenuating post-traumatic neurodegeneration and neurological dysfunction.

Pulsatile Femoral Vein Doppler Pattern is a Parameter of Venous Congestion in ICU Patients.

OBJECTIVES: The aim of this study was to evaluate if the presence of a pulsatile femoral vein pattern is an indicator of venous congestion in the intensive care unit (ICU). DESIGN: Retrospective observational study. SETTING: Three medico-surgical university-affiliated ICUs. PARTICIPANTS: Adult patients who had an ultrasound evaluation at several time points during their ICU stay: at baseline (within 24 hours of admission to ICU), daily during their ICU stay, and within 24 hours before ICU discharge. INTERVENTIONS: At each time point, the hemodynamic, respiratory, and cardiac ultrasound parameters were recorded. The common femoral vein was studied with pulsed-wave Doppler at the level of the femoral trigonum, with high frequency (5-13 MHz) linear array vascular probe and venous vascular mode, in supine patients. MEASUREMENTS AND MAIN RESULTS: One hundred eight patients who underwent 400 ultrasound evaluations (3.7 ± 1 ultrasound evaluations per patient) during their ICU stay were included. Seventy-nine of 108 patients (73%) had a pulsatile femoral vein pattern at least at 1 time point. The multivariable mixed effects logistic regression model demonstrated an association among pulsatile femoral vein pattern, body mass index (OR: 0.91[95% CI 0.85-0.96], p = 0.002), inferior vena cava mean diameter (OR: 2.35 [95% CI 1.18-4.66], p = 0.014), portal vein pulsatility (OR: 2.3 [95% CI 1.2-4.4], p = 0.012), and congestive renal vein flow pattern (OR: 4.02 [95% CI 2.01-8.03], p < 0.001). The results were confirmed by principal component analysis. CONCLUSION: In the ICU, a pulsatile femoral vein pattern is associated with parameters of venous congestion, independently of the patient's volume status, and ventilatory treatment. These results suggest the femoral vein Doppler pulsatility as a parameter of congestion in ICU patients.

Posterior Shoulder Instability, Part II-Glenoid Bone Grafting, Glenoid Osteotomy, and Rehabilitation/Return to Play-An International Expert Delphi Consensus Statement.

PURPOSE: To establish consensus statements on glenoid bone grafting, glenoid osteotomy, rehabilitation, return to play, and follow-up for posterior shoulder instability. METHODS: A consensus process on the treatment of posterior shoulder instability was conducted, with 71 shoulder/sports surgeons from 12 countries participating on the basis of their level of expertise in the field. Experts were assigned to 1 of 6 working groups defined by specific subtopics within posterior shoulder instability. Consensus was defined as achieving 80% to 89% agreement, whereas strong consensus was defined as 90% to 99% agreement, and unanimous consensus was indicated by 100% agreement with a proposed statement. RESULTS: All of the statements relating to rehabilitation, return to play, and follow-up achieved consensus. There was unanimous consensus that the following criteria should be considered: restoration of strength, range of motion, proprioception, and sport-specific skills, with a lack of symptoms. There is no minimum time point required to return to play. Collision athletes and military athletes may take longer to return because of their greater risk for recurrent instability, and more caution should be exercised in clearing them to return to play, with elite athletes potentially having different considerations in returning to play. The relative indications for revision surgery are symptomatic apprehension, multiple recurrent instability episodes, further intra-articular pathologies, hardware failure, and pain. CONCLUSIONS: The study group achieved strong or unanimous consensus on 59% of statements. Unanimous consensus was reached regarding the criteria for return to play, collision/elite athletes having different considerations in return to play, indications for revision surgery, and imaging only required as routine for those with glenoid bone grafting/osteotomies at subsequent follow-ups. There was no consensus on optimal fixation method for a glenoid bone block, the relative indications for glenoid osteotomy, whether fluoroscopy is required or if the labrum should be concomitantly repaired. LEVEL OF EVIDENCE: Level V, expert opinion.

Use of cardiac imaging in chronic coronary syndromes: the EURECA Imaging registry.

BACKGROUND: The prospective, multicentre EURECA registry assessed the use of imaging and adoption of the European Society of Cardiology (ESC) Guidelines (GL) in patients with chronic coronary syndromes (CCS). METHODS: Between May 2019 and March 2020, 5156 patients were recruited in 73 centres from 24 ESC member countries. The adoption of GL recommendations was evaluated according to clinical presentation and pre-test probability (PTP) of obstructive coronary artery disease (CAD). RESULTS: The mean age of the population was 64 ± 11 years, 60% of patients were males, 42% had PTP >15%, 27% had previous CAD, and ejection fraction was <50% in 5%. Exercise ECG was performed in 32% of patients, stress imaging as the first choice in 40%, and computed tomography coronary angiography (CTCA) in 22%. Invasive coronary angiography (ICA) was the first or downstream test in 17% and 11%, respectively. Obstructive CAD was documented in 24% of patients, inducible ischaemia in 19%, and 13% of patients underwent revascularization. In 44% of patients, the overall diagnostic process did not adopt the GL. In these patients, referral to stress imaging (21% vs. 58%; P < 0.001) or CTCA (17% vs. 30%; P < 0.001) was less frequent, while exercise ECG (43% vs. 22%; P < 0.001) and ICA (48% vs. 15%; P < 0.001) were more frequently performed. The adoption of GL was associated with fewer ICA, higher proportion of diagnosis of obstructive CAD (60% vs. 39%, P < 0.001) and revascularization (54% vs. 37%, P < 0.001), higher quality of life, fewer additional testing, and longer times to late revascularization. CONCLUSIONS: In patients with CCS, current clinical practice does not adopt GL recommendations on the use of diagnostic tests in a significant proportion of patients. When the diagnostic approach adopts GL recommendations, invasive procedures are less frequently used and the diagnostic yield and therapeutic utility are superior.

Photochemical Crosslinking of Tarsal Collagen as a Treatment for Eyelid Laxity: Evaluation in Ex Vivo Human Tissue.

PURPOSE: Experimental investigation in human eyelids to confirm that exposing excised tarsal plates to ultraviolet-A radiation can induce a stiffening effect through the riboflavin-photosensitized crosslinking of tarsal collagen. METHODS: Thirteen tarsal plates excised from nonfrozen human cadavers were irradiated with ultraviolet-A rays (365 nm wavelength) at an irradiance of 75 mW/cm2 for 3 minutes, equivalent to a radiation fluence of 13.5 J/cm2, in the presence of a riboflavin derivative as a photosensitizer. The tensile stress (strength) and Young's modulus (stiffness) of both nonirradiated and irradiated specimens were measured with the BioTester 5000 in the uniaxial mode at a strain of 10% and analyzed statistically. Individual specimens excised from 2 cadavers were also examined by routine histopathologic protocols to assess the effect of radiation on the Meibomian glands and collagen organization. RESULTS: The irradiation enhanced both stiffness and strength of the human tarsal specimens, the difference between the test samples and controls being statistically significant (p < 0.0002 for n = 13). Histology indicated no damage to tarsal connective tissue or to Meibomian glands, and revealed a more compact packing of the collagen network located around the glands, which may be beneficial. The existence of collagen compaction was also supported by the reduction of samples' thickness after irradiation (p = 0.0645). CONCLUSIONS: The irradiation of tarsal tissue with ultraviolet-A light of tarsus appears to be a safe and effective method for reducing eyelid laxity in human patients.

New physics searches at kaon and hyperon factories.

Rare meson decays are among the most sensitive probes of both heavy and light new physics. Among them, new physics searches using kaons benefit from their small total decay widths and the availability of very large datasets. On the other hand, useful complementary information is provided by hyperon decay measurements. We summarize the relevant phenomenological models and the status of the searches in a comprehensive list of kaon and hyperon decay channels. We identify new search strategies for under-explored signatures, and demonstrate that the improved sensitivities from current and next-generation experiments could lead to a qualitative leap in the exploration of light dark sectors.

Intraosseous hibernoma: clinicopathologic and imaging analysis of 18 cases.

AIMS: Intraosseous hibernomas are rarely reported tumours with brown adipocytic differentiation of unknown aetiology, with only 38 cases documented in the literature. We sought to further characterise the clinicopathologic, imaging and molecular features of these tumours. METHODS AND RESULT: Eighteen cases were identified occurring in eight females and 10 males (median age = 65 years, range = 7-75). Imaging indication was cancer surveillance/staging in 11 patients and clinical concern for a metastasis was raised in 13 patients. The innominate bone (7), sacrum (5), mobile spine (4), humerus (1) and femur (1) were involved. Median tumour size was 1.5 cm (range = 0.8-3.8). Tumours were sclerotic (11), mixed sclerotic and lytic (4) or occult (1). Microscopically, tumours were composed of large polygonal cells with distinct cell membranes, finely vacuolated cytoplasm, central or paracentral small bland nuclei with prominent scalloping. Growth around trabecular bone was observed. Tumour cells were immunoreactive for S100 protein (15/15) and adipophilin (5/5), while negative for keratin AE1/AE3(/PCK26) (0/14) and brachyury (0/2). Chromosomal microarray analysis, performed on four cases, did not show clinically significant copy number variation across the genome or on 11q, the site of AIP and MEN1. CONCLUSION: Analysis of 18 cases of intraosseous hibernoma, to our knowledge, the largest series to date, revealed that these tumours are most often detected in the spine and pelvis of older adults. Tumours were generally small, sclerotic and frequently found incidentally and can raise concern for metastasis. Whether or not these tumours are related to soft tissue hibernomas is uncertain.

Quantitative analysis of cross-talk in partly deuterated samples of nuclear spins hyperpolarized by dynamic nuclear polarization (DNP) in the thermal mixing regime.

Dynamical nuclear polarization (DNP) is a powerful method that allows one to polarize virtually any spin-bearing nucleus by transferring electron polarization by microwave irradiation of the electron Zeeman transitions. Under certain conditions, the DNP process can be described in thermodynamical terms using the thermal mixing (TM) model. Different nuclear species can exchange energy indirectly through their interactions with the electron spins and reach a common spin temperature. Such "cross-talk" effects can occur between proton (H) and deuterium (D) nuclei in de- and re-polarization experiments. In this work, we investigate such effects experimentally, using either protonated or deuterated TEMPOL radicals as polarizing agents. An analysis of these experiments based on Provotorov's equations allows one to extract the relevant kinetic parameters, such as the rates of energy transfer between the different reservoirs, and the heat capacity of the non-Zeeman (NZ) electron reservoir, while the heat capacities of the proton and deuterium reservoirs can be estimated based on their usual expressions. These parameters allow one to make predictions of the behaviour of heteronuclei such as carbon-13 or phosphorous-31, provided that their heat capacities are negligible. Finally, we present an experimental study of the dependence of Provotorov's kinetic parameters on the TEMPOL concentration and on the H/D ratio, thus providing insight into the nature of "hidden" spins that are not observable directly because of their proximity to the radicals.

The Loss of Temporal Muscle Volume is Associated with Poor Outcome in Patients with Subarachnoid Hemorrhage: An Observational Cohort Study.

BACKGROUND: Intensive care unit (ICU) acquired weakness is a major contributor to poor functional outcome of ICU patients. Quantification of temporal muscle volume assessed on routine computed tomography (CT) scans may serve as a biomarker for muscle wasting in patients suffering from acute brain injury. METHODS: This is a retrospective analysis of prospectively collected data. Temporal muscle volume was assessed on head CT scans of consecutive patients with spontaneous subarachnoid hemorrhage within prespecified time frames (on admission, then weekly ± 2 days). Whenever possible, temporal muscle volume was assessed bilaterally and averaged for the analysis. Poor functional outcome was defined as a 3-month modified Rankin Scale Score ≥ 3. Statistical analysis was performed using generalized estimating equations to handle repeated measurements within individuals. RESULTS: The analysis comprised 110 patients with a median Hunt & Hess score of 4 (interquartile range 3-5). Median age was 61 (50-70) years, 73 patients (66%) were women. Baseline temporal muscle volume was 18.5 ± 0.78 cm3 and significantly decreased over time (p < 0.001) by a mean of 7.9% per week. Higher disease severity (p = 0.002), hydrocephalus (p = 0.020), pneumonia (p = 0.032), and bloodstream infection (p = 0.015) were associated with more pronounced muscle volume loss. Patients with poor functional outcome had smaller muscle volumes 2 and 3 weeks after subarachnoid hemorrhage compared with those with good outcome (p = 0.025). The maximum muscle volume loss during ICU stay was greater in patients with poor functional outcome (- 32.2% ± 2.5% vs. - 22.7% ± 2.5%, p = 0.008). The hazard ratio for poor functional outcome was 1.027 (95% confidence interval 1.003-1.051) per percent of maximum muscle volume loss. CONCLUSIONS: Temporal muscle volume, which is easily assessable on routine head CT scans, progressively decreases during the ICU stay after spontaneous subarachnoid hemorrhage. Because of its association with disease severity and functional outcome, it may serve as a biomarker for muscle wasting and outcome prognostication.

Outcomes of culture-negative vs. culture-positive infective endocarditis: the ESC-EORP EURO-ENDO registry.

AIM: Fatality of infective endocarditis (IE) is high worldwide, and its diagnosis remains a challenge. The objective of the present study was to compare the clinical characteristics and outcomes of patients with culture-positive (CPIE) vs. culture-negative IE (CNIE). METHODS AND RESULTS: This was an ancillary analysis of the ESC-EORP EURO-ENDO registry. Overall, 3113 patients who were diagnosed with IE during the study period were included in the present study. Of these, 2590 (83.2%) had CPIE, whereas 523 (16.8%) had CNIE. As many as 1488 (48.1%) patients underwent cardiac surgery during the index hospitalization, 1259 (48.8%) with CPIE and 229 (44.5%) with CNIE. The CNIE was a predictor of 1-year mortality [hazard ratio (HR) 1.28, 95% confidence interval (CI) 1.04-1.56], whereas surgery was significantly associated with survival (HR 0.49, 95% CI 0.41-0.58). The 1-year mortality was significantly higher in CNIE than CPIE patients in the medical subgroup, but it was not significantly different in CNIE vs. CPIE patients who underwent surgery. CONCLUSION: The present analysis of the EURO-ENDO registry confirms a higher long-term mortality in patients with CNIE compared with patients with CPIE. This difference was present in patients receiving medical therapy alone and not in those who underwent surgery, with surgery being associated with reduced mortality. Additional efforts are required both to improve the aetiological diagnosis of IE and identify CNIE cases early before progressive disease potentially contraindicates surgery.

Diuretics depletion improves cardiac output and ventriculo-arterial coupling in congestive ICU patients during hemodynamic de-escalation.

PURPOSE: Congestion was shown to hamper organ perfusion, but the exact timing of diuretic initiation during hemodynamic de-escalation in shock is unclear. The aim of this study was to describe the hemodynamic effects of diuretic initiation in the stabilized shock. METHODS: We performed a monocentric, retrospective analysis, in a cardiovascular medico-surgical ICU. We included consecutive resuscitated adult patients, for whom the clinician decided to introduce loop diuretic treatment for clinical signs of fluid overload. The patients were hemodynamically evaluated at the moment of diuretic introduction and 24 h later. RESULTS: Seventy ICU patients were included in this study, with a median duration of ICU stay before diuretic initiation of 2 [1-3] days. 51(73%) patients were classified as congestive (central venous pressure > 12 mmHg). After treatment, the cardiac index increased towards normal values in the congestive group (2.7 ± 0.8 L min- 1 m- 2 from 2.5 ± 0.8 L min- 1 m- 2, p = 0.042), but not in the non-congestive group (2.7 ± 0.7 L min- 1 m- 2 from baseline 2.7 ± 0.8 L min- 1 m- 2, p = 0.968). A decrease in arterial lactate concentrations was observed in the congestive group (2.1 ± 2 mmol L- 1 vs. 1.3 ± 0.6 mmol L- 1, p < 0.001). The diuretic therapy was associated with an improvement of ventriculo-arterial coupling comparing with baseline values in the congestive group (1.69 ± 1 vs. 1.92 ± 1.5, p = 0.03). The norepinephrine use decreased in congestive patients (p = 0.021), but not in the non-congestive group (p = 0.467). CONCLUSION: The initiation of diuretics in ICU congestive patients with stabilized shock was associated with improvement of cardiac index, ventriculo-arterial coupling, and tissue perfusion parameter. These effects were not observed in non-congestive patients.

The impact of Canadian-produced research on the global orthopedic literature: a bibliometric analysis.

BACKGROUND: Little is known about the quality and impact of Canadian-produced research relative to that of other developed nations. The purpose of this study was to determine the contribution of Canadian authors to the orthopedic literature globally and nationally as well as Canada's research productivity in orthopedics. We hypothesized that Canada ranks among the most impactful countries in terms of orthopedic research productivity. METHODS: We performed a bibliometric analysis to identify articles published between 2001 and 2020 in the category of orthopedics. We identified Canada's global rank in terms of overall productivity and assessed the contributions of individual Canadian authors. We also examined the quality of publications as determined by category normalized citation impact (CNCI) and publication in the top quartile of journals (%Q1) in terms of impact factor. In addition, we calculated the percentage of Canadian publications that were in orthopedics. RESULTS: We identified 10 821 orthopedic publications from 2001 to 2020. Canada placed sixth globally in terms of productivity in orthopedic research. The annual productivity of Canadian orthopedic researchers increased over the study period by a factor of 3.2. In terms of research quality, with a %Q1 of 36.5% and a CNCI of 1.22, Canada outperformed Asian countries and the United States; the latter country had a %Q1 of 35.3% and a CNCI of 1.14 over the study period. CONCLUSION: The body of Canadian orthopedic literature has grown consistently over the past 20 years. Despite the overall leadership of the United States and other developed nations such as China and Japan, Canada ranks among the most influential countries in terms of the quality and quantity of orthopedic research.

Quark and Lepton Compositeness: A Renormalizable Model.

In the chiral SU(15) gauge theory presented here, the quarks and leptons are bound states ("prebaryons") of massless preons. The standard model charges of the preons imply three generations of quarks and leptons, plus some vectorlike fermions lighter than the confining scale Λ_{pre}. Under certain assumptions about the chiral dynamics, bound states of two prebaryons behave as Higgs fields. The QCD and electroweak groups may unify above Λ_{pre}, while SU(15) prevents rapid proton decay.

Doppler study of portal vein and renal venous velocity predict the appropriate fluid response to diuretic in ICU: a prospective observational echocardiographic evaluation.

BACKGROUND: Fluid overload and venous congestion are associated with morbi-mortality in the ICU (intensive care unit). Administration of diuretics to correct the fluid balance is common, although there is no strong relationship between the consequent fluid loss and clinical improvement. The aim of the study was to evaluate the ability of the portal pulsatility index, the renal venous impedance index, and the VEXUS score (venous ultrasound congestion score) to predict appropriate diuretic-induced fluid depletion. METHODS: The study had a prospective, observational, single-center observational design and was conducted in a university-affiliated medico-surgical ICU. Adult patients for whom the clinician decided to introduce loop diuretic treatment were included. Hemodynamic and ultrasound measurements (including the portal pulsatility index, renal venous impedance index and VEXUS score) were performed at inclusion and 2 hours after the initiation of the diuretics. The patients' characteristics were noted at inclusion, 24 h later, and at ICU discharge. The appropriate diuretic-induced fluid depletion was defined by a congestive score lower than 3 after diuretic fluid depletion. The congestive score included clinical and biological parameters of congestion. RESULTS: Eighty-one patients were included, and 43 (53%) patients presented with clinically significant congestion score at inclusion. Thirty-four patients (42%) had an appropriate response to diuretic-induced fluid depletion. None of the left- and right-sided echocardiographic parameters differed between the two groups. The baseline portal pulsatility index was the best predictor of appropriate response to diuretic-induced fluid depletion (AUC = 0.80, CI95%:0.70-0.92, p = 0.001), followed by the renal venous impedance index (AUC = 0.72, CI95% 0.61-0.84, p = 0.001). The baseline VEXUS score (AUC of 0.66 CI95% 0.53-0.79, p = 0.012) was poorly predictive of appropriate response to diuretic-induced fluid depletion. CONCLUSION: The portal pulsatility index and the renal venous impedance index were predictive of the appropriate response to diuretic-induced fluid depletion in ICU patients. The portal pulsatility index should be evaluated in future randomized studies.

Effects of self-hydrogen bonding among formamide molecules on the UCST-type liquid-liquid phase separation of binary solutions with imidazolium-based ionic liquid, [Cnmim][TFSI], studied by NMR, IR, MD simulations, and SANS.

The upper critical solution temperature (UCST)-type liquid-liquid phase separation of imidazolium-based ionic liquids (ILs), 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([Cnmim][TFSI], where n represents the alkyl chain length of the cation, n = 6, 8, 10, and 12) binary solutions with formamide (FA) was examined as a function of temperature and the FA mole fraction xFA. The two-phase region (immiscible region) of the solutions is much larger and expands more with the increase in n, in comparison with the previous [Cnmim][TFSI]-1,4-dioxane (1,4-DIO) systems. An array of spectroscopic techniques, including 1H and 13C NMR and IR combined with molecular dynamics (MD) simulations, was conducted on the present binary systems to clarify the microscopic interactions that contribute to the phase-separation mechanism. The hydrogen-bonding interactions of the imidazolium ring H atoms are more favorable with the O atoms of the FA molecules than with 1,4-DIO molecules, whereas the latter interact more favorably with the alkyl chain of the cation. Upon lowering the temperature, the FA molecules gradually self-aggregate through self-hydrogen bonding to form FA clusters. Concomitantly, clusters of ILs are formed via the electrostatic interaction between the counter ions and the dispersion force among the IL alkyl chains. Small-angle neutron scattering (SANS) experiments on the [C6mim][TFSI]-FA-d2 and [C8mim][TFSI]-FA-d2 systems revealed, similarly to [Cnmim][TFSI]-1,4-DIO systems, the crossover of the mechanism from the 3D-Ising mechanism around the UCST xFA to the mean-field mechanism at both sides of the mole fraction. Interestingly, the xFA range of the 3D-Ising mechanism for the FA systems is wider compared with the range of the 1,4-DIO systems. In this way, the self-hydrogen bonding among FA molecules most significantly governs the phase equilibria of the [Cnmim][TFSI]-FA systems.

A single methyl group drastically changes urea's hydration dynamics.

The amphiphilicity and denaturation efficiency of urea can be tuned via alkylation. Although the interaction of alkylureas with water and proteins has been studied in detail, hydration of 1-methylurea has remained elusive, precluding the isolation of the effect of an individual methyl group. Here, we study water dynamics in the hydration shell of 1-methylurea (1-MU) using infrared absorption and ultrafast infrared spectroscopies. We find that 1-MU hardly affects the hydrogen-bond distribution of water as probed by the OD stretching vibration of HOD molecules. Polarization resolved infrared pump-probe experiments reveal that 1-MU slows down the rotational dynamics of up to 3 water molecules in its hydration shell. A comparison to earlier results for other alkylureas suggests that further alkylation does not necessarily slow down the rotational dynamics of additional water molecules. Two-dimensional infrared experiments show that 1-MU markedly slows down the hydrogen-bond fluctuation dynamics of water, yet similar to what has been found for urea and dimethylureas. Remarkably, (alkyl-)ureas that share a similar effect on water's hydrogen-bond fluctuation dynamics have a similar (modest) protein denaturation tendency. As such, not only the hydrophobicity but also hydration of hydrophilic fragments of alkylureas may be relevant to explain their function toward biomolecules.