Vibrational and electronic spectra of protonated vanillin: exploring protonation sites and isomerisation.

Photofragmentation spectra of protonated vanillin produced under electrospray ionisation (ESI) conditions have been recorded in the 3000-3700 cm-1 (vibrational) and 225-460 nm (electronic) ranges, using room temperature IRMPD (infrared multiphoton dissociation) and cryogenic UVPD (ultraviolet photodissociation) spectroscopies, respectively. The cold (∼50 K) electronic UVPD spectrum exhibits very well resolved vibrational structure for the S1 ← S0 and S3 ← S0 transitions, suggesting long excited state dynamics, similar to its simplest analogue, protonated benzaldehyde. The experimental data were combined with theoretical calculations to determine the protonation site and configurational isomer observed in the experiments.

Flux and fluence effects on the vacuum-UV photodesorption and photoprocessing of CO2 ices.

CO2 is a major component of the icy mantles surrounding dust grains in planet and star formation regions. Understanding its photodesorption is crucial for explaining gas phase abundances in the coldest environments of the interstellar medium irradiated by vacuum-UV (VUV) photons. Photodesorption yields determined experimentally from CO2 samples grown at low temperatures (T = 15 K) have been found to be very sensitive to experimental methods and conditions. Several mechanisms have been suggested for explaining the desorption of CO2, O2 and CO from CO2 ices. In the present study, the cross-sections characterizing the dynamics of photodesorption as a function of photon fluence (determined from released molecules in the gas phase) and of ice composition modification (determined in situ in the solid phase) are compared for the first time for different photon flux conditions (from 7.3 × 1012 photon per s cm-2 to 2.2× 1014 photon per s cm-2) using monochromatic synchrotron radiation in the VUV range (on the DESIRS beamline at SOLEIL). This approach reveals that CO and O2 desorptions are decorrelated from that of CO2. CO and O2 photodesorption yields depend on photon flux conditions and can be linked to surface chemistry. In contrast, the photodesorption yield of CO2 is independent of the photon flux conditions and can be linked to bulk ice chemical modification, consistently with indirect desorption induced by an electronic transition (DIET) process.

Monitoring Drug Safety in Pregnancy with Scan Statistics: A Comparison of Two Study Designs.

BACKGROUND: Traditional surveillance of adverse infant outcomes following maternal medication exposures relies on pregnancy exposure registries, which are often underpowered. We characterize the statistical power of TreeScan, a data mining tool, to identify potential signals in the setting of perinatal medication exposures and infant outcomes. METHODS: We used empirical data to inform background incidence of major congenital malformations and other birth conditions. Statistical power was calculated using two probability models compatible with TreeScan, Bernoulli and Poisson, while varying the sample size, magnitude of the risk increase, and incidence of a specified outcome. We also simulated larger referent to exposure matching ratios when using the Bernoulli model in the setting of fixed N:1 propensity score matching. Finally, we assessed the impact of outcome misclassification on power. RESULTS: The Poisson model demonstrated greater power to detect signals than the Bernoulli model across all scenarios and suggested a sample size of 4,000 exposed pregnancies is needed to detect a twofold increase in risk of a common outcome (approximately 8 per 1,000) with 85% power. Increasing the fixed matching ratio with the Bernoulli model did not reliably increase power. An outcome definition with high sensitivity is expected to have somewhat greater power to detect signals than an outcome definition with high positive predictive value. CONCLUSIONS: Use of the Poisson model with an outcome definition that prioritizes sensitivity may be optimal for signal detection. TreeScan is a viable method for surveillance of adverse infant outcomes following maternal medication use.

Evolutionary analysis of the LORELEI gene family in plants reveals regulatory subfunctionalization.

A signaling complex comprising members of the LORELEI (LRE)-LIKE GPI-anchored protein (LLG) and Catharanthus roseus RECEPTOR-LIKE KINASE 1-LIKE (CrRLK1L) families perceive RAPID ALKALINIZATION FACTOR (RALF) peptides and regulate growth, reproduction, immunity, and stress responses in Arabidopsis (Arabidopsis thaliana). Genes encoding these proteins are members of multigene families in most angiosperms and could generate thousands of signaling complex variants. However, the links between expansion of these gene families and the functional diversification of this critical signaling complex as well as the evolutionary factors underlying the maintenance of gene duplicates remain unknown. Here, we investigated LLG gene family evolution by sampling land plant genomes and explored the function and expression of angiosperm LLGs. We found that LLG diversity within major land plant lineages is primarily due to lineage-specific duplication events, and that these duplications occurred both early in the history of these lineages and more recently. Our complementation and expression analyses showed that expression divergence (i.e. regulatory subfunctionalization), rather than functional divergence, explains the retention of LLG paralogs. Interestingly, all but one monocot and all eudicot species examined had an LLG copy with preferential expression in male reproductive tissues, while the other duplicate copies showed highest levels of expression in female or vegetative tissues. The single LLG copy in Amborella trichopoda is expressed vastly higher in male compared to in female reproductive or vegetative tissues. We propose that expression divergence plays an important role in retention of LLG duplicates in angiosperms.

Photodetachment of Deprotonated R-Mandelic Acid: The Role of Proton Delocalization on the Radical Stability.

The photodetachment and stability of R-Mandelate, the deprotonated form of the R-Mandelic acid, was investigated by observing the neutral species issued from either simple photodetachment or dissociative photodetachment in a cold anions set-up. R-Mandalate has the possibility to form an intramolecular ionic hydrogen-bond between adjacent hydroxyl and carboxylate groups. The potential energy surface along the proton transfer (PT) coordinate between both groups (O- …H+ …- OCO) features a single local minima, with the proton localized on the O- group (OH…- OCO). However, the structure with the proton localized on the - OCO group (O- …HOCO) is also observed because it falls within the extremity of the vibrational wavefunction of the OH…- OCO isomer along the PT coordinate. The stability of the corresponding radicals, produced upon photodetachment, is strongly dependent on the position of the proton in the anion: the radicals produced from the OH…- OCO isomer decarboxylate without barrier, while the radicals produced from the O- …HOCO isomer are stable.

Infrared photodesorption of CO from astrophysically relevant ices studied with a free-electron laser.

The infrared excitation and photodesorption of carbon monoxide (CO) and water-containing ices have been investigated using the FEL-2 free-electron laser light source at the FELIX laboratory, Radboud University, The Netherlands. CO-water mixed ices grown on a gold-coated copper substrate at 18 K were investigated. No CO photodesorption was observed, within our detection limits, following irradiation with light resonant with the C-O vibration (4.67 µm). CO photodesorption was seen as a result of irradiation with infrared light resonant with water vibrational modes at 2.9 µm and 12 µm. Changes to the structure of the water ice, which modifies the environment of the CO in the mixed ice, were also seen subsequent to irradiation at these wavelengths. No water desorption was observed at any wavelength of irradiation. Photodesorption at both wavelengths is due to a single-photon process. Photodesorption arises due to a combination of fast and slow processes of indirect resonant photodesorption (fast), and photon-induced desorption resulting from energy accumulation in the librational heat bath of the solid water (slow) and metal-substrate-mediated laser-induced thermal desorption (slow). Estimated cross-sections for the slow processes at 2.9 µm and 12 µm were found to be ∼7.5 × 10-18 cm2 and ∼4.5 × 10-19 cm2, respectively.

Protomers of the green and cyan fluorescent protein chromophores investigated using action spectroscopy.

The photophysics of biochromophore ions often depends on the isomeric or protomeric distribution, yet this distribution, and the individual isomer contributions to an action spectrum, can be difficult to quantify. Here, we use two separate photodissociation action spectroscopy instruments to record electronic spectra for protonated forms of the green (pHBDI+) and cyan (Cyan+) fluorescent protein chromophores. One instrument allows for cryogenic (T = 40 ± 10 K) cooling of the ions, while the other offers the ability to perform protomer-selective photodissociation spectroscopy. We show that both chromophores are generated as two protomers when using electrospray ionisation, and that the protomers have partially overlapping absorption profiles associated with the S1 ← S0 transition. The action spectra for both species span the 340-460 nm range, although the spectral onset for the pHBDI+ protomer with the proton residing on the carbonyl oxygen is red-shifted by ≈40 nm relative to the lower-energy imine protomer. Similarly, the imine and carbonyl protomers are the lowest energy forms of Cyan+, with the main band for the carbonyl protomer red-shifted by ≈60 nm relative to the lower-energy imine protomer. The present strategy for investigating protomers can be applied to a wide range of other biochromophore ions.

Novel methods for pregnancy drug safety surveillance in the FDA Sentinel System.

PURPOSE: It is a priority of the US Food and Drug Administration (FDA) to monitor the safety of medications used during pregnancy. Pregnancy exposure registries and cohort studies utilizing electronic health record data are primary sources of information but are limited by small sample sizes and limited outcome assessment. TreeScan™, a statistical data mining tool, can be applied within the FDA Sentinel System to simultaneously identify multiple potential adverse neonatal and infant outcomes after maternal medication exposure. METHODS: We implemented TreeScan using the Sentinel analytic tools in a cohort of linked live birth deliveries and infants nested in the IBM MarketScan® Research Database. As a case study, we compared first trimester fluoroquinolone use and cephalosporin use. We used the Bernoulli and Poisson TreeScan statistics with compatible propensity score-based study designs for confounding control (matching and stratification) and used multiple propensity score models with various strategies for confounding control to inform best practices. We developed a hierarchical outcome tree including major congenital malformations and outcomes of gestational length and birth weight. RESULTS: A total of 1791 fluoroquinolone-exposed and 8739 cephalosporin-exposed mother-infant pairs were eligible for analysis. Both TreeScan analysis methods resulted in single alerts that were deemed to be due to uncontrolled confounding or otherwise not warranting follow-up. CONCLUSIONS: In this implementation of TreeScan using Sentinel analytic tools, we did not observe any new safety signals for fluoroquinolone use in the first trimester. TreeScan, with tailored or high-dimensional propensity scores for confounding control, is a valuable tool in addition to current safety surveillance methods for medications used during pregnancy.

Pre-Dewar structure modulates protonated azaindole photodynamics.

Recent experimental work revealed that the lifetime of the S3 state of protonated 7-azaindole is about ten times longer than that of protonated 6-azaindole. We simulated the nonradiative decay pathways of these molecules using trajectory surface hopping dynamics after photoexcitation into S3 to elucidate the reason for this difference. Both isomers mainly follow a common ππ* relaxation pathway involving multiple state crossings while coming down from S3 to S1 in the subpicosecond time scale. However, the simulations reveal that the excited-state topographies are such that while the 6-isomer can easily access the region of nonadiabatic transitions, the internal conversion of the 7-isomer is delayed by a pre-Dewar bond formation with a boat conformation.

IRFEL Selective Irradiation of Amorphous Solid Water: from Dangling to Bulk Modes.

Amorphous solid water (ASW) is one of the most widely studied solid phase systems. A better understanding of the nature of inter- and intramolecular forces in ASW is, however, still required to correctly interpret the catalytic role of ASW in the formation and preservation of molecular species in environments such as the icy surfaces of Solar System objects, on interstellar icy dust grains, and potentially even in the upper layers of the Earth's atmosphere. In this work, we have systematically exposed porous ASW (pASW) to mid-infrared radiation generated by a free-electron laser at the HFML-FELIX facility in The Netherlands to study the effect of vibrational energy injection into the surface and bulk modes of pASW. During multiple sequential irradiations on the same ice spot, we observed selective effects both at the surface and in the bulk of the ice. Although the density of states in pASW should allow for a fast vibrational relaxation through the H-bonded network, part of the injected energy is converted into structural ice changes as illustrated by the observation of spectral modifications when performing Fourier transform infrared spectroscopy in reflection-absorption mode. Future studies will include the quantification of such effects by systematically investigating ice thickness, ice morphology, and ice composition.

Energy Transfer and Restructuring in Amorphous Solid Water upon Consecutive Irradiation.

Interstellar and cometary ices play an important role in the formation of planetary systems around young stars. Their main constituent is amorphous solid water (ASW). Although ASW is widely studied, vibrational energy dissipation and structural changes due to vibrational excitation are less well understood. The hydrogen-bonding network is likely a crucial component in this. Here, we present experimental results on hydrogen-bonding changes in ASW induced by the intense, nearly monochromatic mid-IR free-electron laser (FEL) radiation of the FELIX-2 beamline at the HFML-FELIX facility at the Radboud University in Nijmegen, The Netherlands. Structural changes in ASW are monitored by reflection-absorption infrared spectroscopy and depend on the irradiation history of the ice. The experiments show that FEL irradiation can induce changes in the local neighborhood of the excited molecules due to energy transfer. Molecular dynamics simulations confirm this picture: vibrationally excited molecules can reorient for a more optimal tetrahedral surrounding without breaking existing hydrogen bonds. The vibrational energy can transfer through the hydrogen-bonding network to water molecules that have the same vibrational frequency. We hence expect a reduced energy dissipation in amorphous material with respect to crystalline material due to the inhomogeneity in vibrational frequencies as well as the presence of specific hydrogen-bonding defect sites, which can also hamper the energy transfer.

Loss of CO2 from Monodeprotonated Phthalic Acid upon Photodissociation and Dissociative Electron Detachment.

The decarboxylation (CO2 loss) mechanism of cold monodeprotonated phthalic acid was studied in a photodissociation action spectrometer by quantifying mass-selected product anions and neutral particles as a function of the excitation energy. The analysis proceeded by interpreting the translational energy distribution of the generated uncharged products, and with the help of quantum calculations. In particular, this study reveals different fragmentation pathways in the deprotonated anion and in the radical generated upon electron photodetachment. Unlike the behavior found in other deprotonated aryl carboxylic acids, which do not fragment in the anion excited state, a double loss of CO2 molecules takes place in the phthalic monoanion. Moreover, at higher excitation energies the phthalic monoanion experiences decarboxylative photodetachment with a statistical distribution of product translational energies, which contrasts with the impulsive dissociation reactions characteristic of other aryl carboxylic anions.

Influence of the N atom and its position on electron photodetachment of deprotonated indole and azaindole.

Electron photodetachment of cold deprotonated indole and azaindole anions has been studied by use of a mass-selective photofragmentation spectrometer capable of negative ion and neutral particle detection. The electron affinities of the indolyl radical and the 5-, 6- and 7-azaindolyl radicals have been measured with an uncertainty of less than 0.002 eV. The presence of the nitrogen atom in the six-membered ring of the azaindolide anions stabilises the electron by 0.3 to 0.4 eV, i.e. about 10-15%, compared to the indolide anion. No fragmentation was observed in either the anionic or radical forms of the species studied. The appearance of dipole-bound states in the spectra of deprotonated 6- and 7-azaindole anions allowed us to analyse the vibrational structure of the neutral 6- and 7-azaindolyl radicals produced following photodetachment. Although no dipole-bound states were clearly identified for deprotonated indole or 5-azaindole, the shape of the photodetachment threshold suggests the presence of a very weakly dipole-bound state or dipole resonance, which cannot be resolved with our laser resolution.

Influence of the N atom position on the excited state photodynamics of protonated azaindole.

We present a study of the photofragmentation of three protonated azaindole molecules - 7-azaindole, 6-azaindole, and 5-azaindole - consisting of fused pyrrole-pyridine bicyclic aromatic systems, in which the pyridinic (protonated) nitrogen heteroatom is located at the 7, 6, and 5 positions, respectively. Photofragmentation electronic spectra of the isolated aforementioned azaindolinium cations reveal that their photodynamics extends over timescales covering nine orders of magnitude and provide evidence about the resultant fragmentation pathways. Moreover, we show how the position of the heteroatom in the aromatic skeleton influences the excited state energetics, fragmentation pathways, and fragmentation timescales. Computed ab initio adiabatic transition energies are used to assist the assignation of the spectra, while geometry optimisation in the excited electronic states as well as ab initio calculations along the potential surfaces demonstrate the role of ππ*/πσ* coupling and/or large geometry changes in the dynamics of these species. Evidence supporting the formation of Dewar valence isomers as intermediates involved in sub-picosecond relaxation processes is discussed.

Photoinduced water oxidation in pyrimidine-water clusters: a combined experimental and theoretical study.

The photocatalytic oxidation of water with molecular or polymeric N-heterocyclic chromophores is a topic of high current interest in the context of artificial photosynthesis, that is, the conversion of solar energy to clean fuels. Hydrogen-bonded clusters of N-heterocycles with water molecules in a molecular beam are simple model systems for which the basic mechanisms of photochemical water oxidation can be studied under well-defined conditions. In this work, we explored the photoinduced H-atom transfer reaction in pyrimidine-water clusters yielding pyrimidinyl and hydroxyl radicals with laser spectroscopy, mass spectrometry and trajectory-based ab initio molecular dynamics simulations. The oxidation of water by photoexcited pyrimidine is unequivocally confirmed by the detection of the pyrimidinyl radical. The dynamics simulations provide information on the time scales and branching ratios of the reaction. While relaxation to local minima of the S1 potential-energy surface is the dominant reaction channel, the H-atom transfer reaction occurs on ultrafast time scales (faster than about 100 fs) with a branching ratio of a few percent.

Analgesia Use in Children with Acute Long Bone Fractures in the Pediatric Emergency Department.

BACKGROUND: Practice variation exists in pain management of children with long bone fractures (LBFs). OBJECTIVE: The objectives of this study were to describe current pain management in children with LBFs and the factors associated with the undertreatment of pain. METHODS: We retrospectively studied children (aged 0-18 years) with a diagnosis of LBF in a pediatric emergency department (PED) from November 2015 through August 2016. Demographic characteristics and quality measures were noted. We determined the impact of PED crowding using the National Emergency Department Overcrowding Scale. RESULTS: A total of 905 patients (63% male, 48% African American) were enrolled. Median age was 6 years (interquartile range [IQR] 7 years), 72% had upper extremity injuries, falls were the most common mechanism (74%), and the majority were discharged (77%). Median time to pain score was 6 min (IQR 14 min). Seventy-two percent received analgesia with a median time to order of 63 min and medication receipt of 87 min. Ibuprofen was the analgesia prescribed most commonly. There were no identified factors associated with oligoanalgesia. Nonuse of narcotics was associated with African-American race, public insurance, single fractures, and arrival via private vehicle. Ambulance arrivals, lower extremity fractures, and disaster mode were associated with receiving analgesia within 60 min. CONCLUSIONS: In our study, 28% of children with LBFs did not receive pain medications, especially during normal PED volumes. Additional studies are required to explore triage as a venue for analgesia delivery for LBFs.

A 7-Year-Old Boy With Recurring Episodes of Abdominal Pain.

Recurrent abdominal pain is a relatively common complaint in children who present to the emergency department. The etiology is often thought to be psychogenic, with an underlying organic cause present in less than 10% of patients. Intermittent ureteropelvic junction obstruction is usually not considered in the differential diagnosis of recurrent acute abdominal pain in children, which can cause a significant delay in diagnosis. In this condition, intermittent obstruction of the flow of urine from the renal pelvis to the proximal ureter occurs, which causes intermittent acute colicky abdominal pain and vomiting. This acute event, often referred to as a Dietl's crisis, either subsides after several hours or prompts a visit to the emergency department. Management often focuses on the identification of psychosocial issues or constipation, and routine abdominal imaging is not a common practice. The frequency of these events over time and the duration of each acute event are 2 components that factor into determining the loss of function in the affected kidney. The purpose of this case report is to increase awareness of intermittent ureteropelvic junction obstruction as a cause of recurring episodes of acute abdominal pain in children. Emphasis in this case report is on Dietl's crisis, how it presents, and how it is diagnosed and managed.

The Role of LORELEI in Pollen Tube Reception at the Interface of the Synergid Cell and Pollen Tube Requires the Modified Eight-Cysteine Motif and the Receptor-Like Kinase FERONIA.

In angiosperms, pollen tube reception by the female gametophyte is required for sperm release and double fertilization. In Arabidopsis thaliana lorelei (lre) mutants, pollen tube reception fails in most female gametophytes, which thus remain unfertilized. LRE encodes a putative glycosylphosphatidylinositol (GPI)-anchored surface protein with a modified eight-cysteine motif (M8CM). LRE fused to citrine yellow fluorescent protein (LRE-cYFP) remains functional and localizes to the synergid plasma membrane-rich filiform apparatus, the first point of contact between the pollen tube and the female gametophyte. Structure-function analysis using LRE-cYFP showed that the role of LRE in pollen tube reception requires the M8CM, but not the domains required for GPI anchor addition. Consistently, LRE-cYFP-TM, where GPI anchor addition domains were replaced with a single-pass transmembrane domain, fully complemented the pollen tube reception defect in lre-7 female gametophytes. Ectopically expressed and delivered LRE-cYFP from pollen tubes could non-cell-autonomously complement the pollen tube reception defect in lre female gametophytes, only if they expressed FERONIA. Additionally, pollen tube-expressing LRE variants lacking domains critical for GPI anchor addition also rescued lre female gametophyte function. Therefore, LRE and FERONIA jointly function in pollen tube reception at the interface of the synergid cell and pollen tube.

Foraging strategies of individual silky pocket mice over a boom-bust cycle in a stochastic dryland ecosystem.

Small mammals use multiple foraging strategies to compensate for fluctuating resource quality in stochastic environments. These strategies may lead to increased dietary overlap when competition for resources is strong. To quantify temporal contributions of high (C3) versus low quality (C4) resources in diets of silky pocket mice (Perognathus flavus), we used stable carbon isotope (δ13C) analysis of 1391 plasma samples collected over 2 years. Of these, 695 samples were from 170 individuals sampled ≥ 3 times across seasons or years, allowing us to assess changes in dietary breadth at the population and individual levels across a boom-bust population cycle. In 2014, the P. flavus population increased to 412 captures compared to 8 captures in prior and subsequent years, while populations of co-occurring small mammals remained stable. As intraspecific competition increased, the population-wide dietary niche of P. flavus did not change, but individual specialization increased significantly. During this period, ~ 27% (41/151) of individuals sampled specialized on C3 resources, which were abundant during the spring and previous fall seasons. Most of the remaining individuals were C3-C4 generalists (64%) (96/151), and only 9% (14/151) specialized on C4 resources. In 2015, P. flavus population density and resource availability declined, individual dietary breadth expanded (84% generalists), no C3 specialists were found, and specialization on C4 resources increased (16%). Our results demonstrate a high degree of inter-individual plasticity in P. flavus foraging strategies, which has implications for how this species will respond to environmental change that is predicted to decrease C3 resources in the future.

Photodetachment of deprotonated aromatic amino acids: stability of the dehydrogenated radical depends on the deprotonation site.

While aromatic amino acids in their deprotonated form have been well characterized by IR and photoelectron spectroscopies, no information is available on the neutral dehydrogenated radicals and, in particular, on their stability when the deprotonation site is changed. This is investigated by observing the neutral fragment issued from either simple photodetachment or dissociative photodetachment of the deprotonated aromatic amino acids phenylalanine, tyrosine, and tryptophan. We show that the dehydrogenated radicals of aromatic amino acids produced upon photodetachment of molecules deprotonated on the carbonyl group dissociate without barrier, leading to the formation of CO2 and a radical amine. However, when the system is deprotonated on functional groups located on the chromophore, the radicals produced by photodetachment are stable, indicating the important photostabilizing role played by functional groups.