Time-resolved structural studies of protein reaction dynamics: a smorgasbord of X-ray approaches

Time-resolved structural studies of proteins have undergone several significant developments during the last decade. Recent developments using time-resolved X-ray methods, such as time-resolved Laue diffraction, low-temperature intermediate trapping, time-resolved wide-angle X-ray scattering and time-resolved X-ray absorption spectroscopy, are reviewed

The kinetic dose limit in room-temperature time-resolved macromolecular crystallography

The effect of the X-ray dose on room-temperature time-resolved Laue data is discussed

Radiation damage in macromolecular crystallography: what is it and why should we care?

The basic causes of the radiation damage inflicted on macromolecular crystals during diffraction experiments are summarized, as well as the current state of research which attempts to understand and to mitigate it

Orbital Architectures of Planet-Hosting Binaries:I. Forming Five Small Planets in the Truncated Disk of Kepler-444A

We present the first results from our Keck program investigating the orbital architectures of planet-hosting multiple star systems. Kepler-444 is a metal-poor triple star system that hosts five sub-Earth-sized planets orbiting the primary star (Kepler-444A), as well as a spatially unresolved pair of M dwarfs (Kepler-444BC) at a projected distance of 1.8" (66 AU). We combine our Keck/NIRC2 adaptive optics astrometry with multi-epoch Keck/HIRES RVs of all three stars to determine a precise orbit for the BC pair around A, given their empirically constrained masses. We measure minimal astrometric motion ($1.0\pm0.6$ mas yr$^{-1}$, or $0.17\pm0.10$ km s$^{-1}$), but our RVs reveal significant orbital velocity ($1.7\pm0.2$ km s$^{-1}$) and acceleration ($7.8\pm0.5$ m s$^{-1}$ yr$^{-1}$). We determine a highly eccentric stellar orbit ($e=0.864\pm0.023$) that brings the tight M dwarf pair within $5.0^{+0.9}_{-1.0}$ AU of the planetary system. We validate that the system is dynamically stable in its present configuration via n-body simulations. We find that the A$-$BC orbit and planetary orbits are likely aligned (98%) given that they both have edge-on orbits and misalignment induces precession of the planets out of transit. We conclude that the stars were likely on their current orbits during the epoch of planet formation, truncating the protoplanetary disk at $\approx$2 AU. This truncated disk would have been severely depleted of solid material from which to form the total $\approx$1.5 $M_{\rm Earth}$ of planets. We thereby strongly constrain the efficiency of the conversion of dust into planets and suggest that the Kepler-444 system is consistent with models that explain the formation of more typical close-in Kepler planets in normal, not truncated, disks.Comment: accepted to Ap

Temperature-dependent macromolecular X-ray crystallography

The dynamical behaviour of crystalline macromolecules and their surrounding solvent as a function of cryo-temperature is reviewed

Identifying associations between diabetes and acute respiratory distress syndrome in patients with acute hypoxemic respiratory failure: an analysis of the LUNG SAFE database

Background: Diabetes mellitus is a common co-existing disease in the critically ill. Diabetes mellitus may reduce the risk of acute respiratory distress syndrome (ARDS), but data from previous studies are conflicting. The objective of this study was to evaluate associations between pre-existing diabetes mellitus and ARDS in critically ill patients with acute hypoxemic respiratory failure (AHRF). Methods: An ancillary analysis of a global, multi-centre prospective observational study (LUNG SAFE) was undertaken. LUNG SAFE evaluated all patients admitted to an intensive care unit (ICU) over a 4-week period, that required mechanical ventilation and met AHRF criteria. Patients who had their AHRF fully explained by cardiac failure were excluded. Important clinical characteristics were included in a stepwise selection approach (forward and backward selection combined with a significance level of 0.05) to identify a set of independent variables associated with having ARDS at any time, developing ARDS (defined as ARDS occurring after day 2 from meeting AHRF criteria) and with hospital mortality. Furthermore, propensity score analysis was undertaken to account for the differences in baseline characteristics between patients with and without diabetes mellitus, and the association between diabetes mellitus and outcomes of interest was assessed on matched samples. Results: Of the 4107 patients with AHRF included in this study, 3022 (73.6%) patients fulfilled ARDS criteria at admission or developed ARDS during their ICU stay. Diabetes mellitus was a pre-existing co-morbidity in 913 patients (22.2% of patients with AHRF). In multivariable analysis, there was no association between diabetes mellitus and having ARDS (OR 0.93 (0.78-1.11); p = 0.39), developing ARDS late (OR 0.79 (0.54-1.15); p = 0.22), or hospital mortality in patients with ARDS (1.15 (0.93-1.42); p = 0.19). In a matched sample of patients, there was no association between diabetes mellitus and outcomes of interest. Conclusions: In a large, global observational study of patients with AHRF, no association was found between diabetes mellitus and having ARDS, developing ARDS, or outcomes from ARDS. Trial registration: NCT02010073. Registered on 12 December 2013

Hyperoxemia and excess oxygen use in early acute respiratory distress syndrome : Insights from the LUNG SAFE study

Publisher Copyright: © 2020 The Author(s). Copyright: Copyright 2020 Elsevier B.V., All rights reserved.Background: Concerns exist regarding the prevalence and impact of unnecessary oxygen use in patients with acute respiratory distress syndrome (ARDS). We examined this issue in patients with ARDS enrolled in the Large observational study to UNderstand the Global impact of Severe Acute respiratory FailurE (LUNG SAFE) study. Methods: In this secondary analysis of the LUNG SAFE study, we wished to determine the prevalence and the outcomes associated with hyperoxemia on day 1, sustained hyperoxemia, and excessive oxygen use in patients with early ARDS. Patients who fulfilled criteria of ARDS on day 1 and day 2 of acute hypoxemic respiratory failure were categorized based on the presence of hyperoxemia (PaO2 > 100 mmHg) on day 1, sustained (i.e., present on day 1 and day 2) hyperoxemia, or excessive oxygen use (FIO2 ≥ 0.60 during hyperoxemia). Results: Of 2005 patients that met the inclusion criteria, 131 (6.5%) were hypoxemic (PaO2 < 55 mmHg), 607 (30%) had hyperoxemia on day 1, and 250 (12%) had sustained hyperoxemia. Excess FIO2 use occurred in 400 (66%) out of 607 patients with hyperoxemia. Excess FIO2 use decreased from day 1 to day 2 of ARDS, with most hyperoxemic patients on day 2 receiving relatively low FIO2. Multivariate analyses found no independent relationship between day 1 hyperoxemia, sustained hyperoxemia, or excess FIO2 use and adverse clinical outcomes. Mortality was 42% in patients with excess FIO2 use, compared to 39% in a propensity-matched sample of normoxemic (PaO2 55-100 mmHg) patients (P = 0.47). Conclusions: Hyperoxemia and excess oxygen use are both prevalent in early ARDS but are most often non-sustained. No relationship was found between hyperoxemia or excessive oxygen use and patient outcome in this cohort. Trial registration: LUNG-SAFE is registered with ClinicalTrials.gov, NCT02010073publishersversionPeer reviewe

Bleeding to death from cut K2: a case of synthetic marijuana induced coagulopathy

Introduction: There has been a major increase in synthetic marijuana use in recent times as it considered a “safe” alternative to cannabinoid use. Unfortunately, as the composition is unknown, so are the side effects. We are presenting this case to bring awareness for one of the many life threatening side effects of synthetic marijuana use. Case Description: Our patient is a 41 year old female presenting with hematuria, menorrhagia, and spontaneous bruising. She endorsed use of ‘K2’ synthetic marijuana (SM) four days prior to onset of symptoms. She denied any medications or history of coagulopathy. Initial labs revealed hemoglobin 4.2 g/dL (baseline: 10 g/dL), PTT: 175 seconds (25-35 seconds), and undetectable INR. CT abdomen did not show hemorrhage. With recent K2 use and signs and symptoms consistent with coagulopathy, our concern was for contaminated K2. Anticoagulant poisoning panel was positive for brodifacoum. She was treated with FFP, PRBCs, oral and IV vitamin K. INR improved to 1.7, PTT 45. Patient was discharged on Vitamin K 10 mg three times daily. Discussion: The incidence of SM contamination leading to life threatening coagulopathy has only recently been identified. Little is known regarding the composition of SM or mechanism leading to coagulopathy. However, brodifacoum has been implicated as the culprit. This compound acts by inhibiting vitamin K epoxide reductase and is 100x more potent than warfarin. Half-ife is between 20-150 days and symptoms can present up to three months after use. Presenting symptoms can include epistaxis, melena, menorrhagia, and spontaneous intracranial hemorrhage. Labs will reveal elevated INR, prolonged PTT, and acute anemia. An anticoagulant poisoning panel is necessary to confirm presence of toxins. Treatment includes FFP or prothrombin complex concentrate with vitamin K. Duration of therapy is undetermined, but may be more than 6 months of oral vitamin K. Conclusion: Maintain a high index of suspicion for brodifacoum poisoning with new onset coagulopathy. Treatment include FFP, repeated, high dose vitamin K supplementation while simultaneously contacting poison control. Patient education is of upmost importance

That feeling when your heart\u27s hard work is not enough: high output heart failure

Introduction: High output heart failure (HOHF) can be caused by chronic conditions, including severe anemia, hypoxia, obesity, acutely by septic shock, and hemorrhage. Basically, the heart is normal and there’s no “pump” failure. The main problem is the underlying decrease in systemic vascular resistance ,that drives low blood pressure, and activation of neurohormonal mechanisms, favoring salt and water retention. Case Description: A 58-year-old male presents after developing shortness-of-breath at rest for two days. He reported diet and medications compliance. Patient noticed to have a lower extremity edema. He was hypotensive with BP 83/57. Chest x-ray revealed vascular congestion with cephalization. BNP was found to be elevated. EKG and troponin were unremarkable. 2D echocardiography revealed hyper-dynamic left ventricular systolic function with ejection fraction of 84 %. Patient has been admitted five times over the past four months with similar presentations. Following each admission, he underwent aggressive diuresis and subsequently discharged home on Frusemide, conferring a diagnosis of diastolic heart failure. It was noted, that patient had those frequent admissions after developing chronic anemia, as low as Hgb of 6.8 mg/dl. He had rick factors for HOF including anemia, chronic hypoxemia secondary to tobacco abuse, and obesity. His estimated cardiac output was 7.6 L/min and estimated mixed venous oxygen saturation was 10.7%, all speaks for HOHF. Patient cautiously diuresed. Hematology was involved to address the anemia. Conclusion: This case illustrates patients with HOHF are overlooked and sometimes aggressively diuresed, which could be deleterious. It is recommended that HOHF patients should be diuresed cautiously because preload is needed to avoid functional outflow obstruction. Management should focus on treating the underlying causes