Genome-sequencing studies indicate that all humans carry many genetic variants predicted to cause loss of function (LoF) of protein-coding genes, suggesting unexpected redundancy in the human genome. ...Here we apply stringent filters to 2951 putative LoF variants obtained from 185 human genomes to determine their true prevalence and properties. We estimate that human genomes typically contain ~100 genuine LoF variants with ~20 genes completely inactivated. We identify rare and likely deleterious LoF alleles, including 26 known and 21 predicted severe disease—causing variants, as well as common LoF variants in nonessential genes. We describe functional and evolutionary differences between LoF-tolerant and recessive disease genes and a method for using these differences to prioritize candidate genes found in clinical sequencing studies.
Asphaltenes have traditionally been conceived as highly aromatic, alkyl-deficient compounds enriched in pericondensed aromatic “island” motifs. This structural definition evolved into the general ...notion that aromatic core-dominated interactions (π-stacking) drive asphaltene aggregation, and heteroatom-based intermolecular forces have no significant effect on the overall solubility and aggregation behavior. However, the exclusion of heteroatoms in asphaltene chemistry is inconsistent with the Boduszynski continuum and known asphaltene properties, such as increased heteroatom content relative to maltenes, interfacial activity, and strong adsorption to polar stationary phases. Thus, to determine whether or not heteroatoms are involved in solubility, we have separated asphaltene fractions enriched in single-core (island) or multicore motifs (archipelago) according to their partitioning in n-heptane by two fractionation methods. In the first separation procedure, the acetone fraction from Wyoming deposit n-heptane asphaltenes (island-enriched) was adsorbed on polytetrafluoroethylene powder and Soxhlet extracted with n-heptane. Subfractions were collected after one day, one week, one month, and three months of extraction, and the residue, n-heptane insoluble material, was recovered with a mixture of toluene and dichloromethane. In the second method, the acetone fraction from Athabasca bitumen n-heptane asphaltenes (archipelago-enriched) was fractionated by differential precipitation in mixtures of n-heptane and toluene. The molecular composition of the asphaltene subfractions was accessed by positive-ion atmospheric pressure photoionization coupled to 9.4 T Fourier transform ion cyclotron resonance mass spectrometry and structures were determined by infrared multiphoton dissociation. The compositional trends for heteroatom content, double bond equivalents, and alkyl substitution suggest that the Boduszynski continuum can be extended to asphaltenes. In particular, the compositional range of polyoxygenated asphaltene compounds shifts toward lower aromaticity, whereas oxygen-depleted species are more aromatic. Moreover, the results demonstrate that polyoxygenated species (e.g., O3 and S2O3 classes) are pivotal in asphaltene solubility, as they concentrate in the most polarizable and insoluble asphaltene subfractions. Therefore, the results support the existence of atypical asphaltene species with remarkably low aromaticity that reside in the most insoluble asphaltene subfractions because of their high heteroatom content. Such asphaltene compounds preferentially ionize as protonated molecules rather than radical cations and overlap the compositional range of interfacially active species, consistent with their tendency to participate in hydrogen bonding. Collectively, the results highlight the need for an asphaltene molecular model based on the existence of polyfunctional species capable of interacting with neighboring asphaltene molecules through several intermolecular forces, including London dispersion forces between aliphatic moieties, π-stacking of aromatic cores, hydrogen bonding between nitrogen and oxygen-containing functionalities, and acid/base interactions between carboxylic acids and pyridine rings.
Detailed characterization of complex biological surfaces by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) requires instrumentation that is capable of high mass ...resolving power, mass accuracy, and dynamic range. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) offers the highest mass spectral performance for MALDI MSI experiments, and often reveals molecular features that are unresolved on lower performance instrumentation. Higher magnetic field strength improves all performance characteristics of FT-ICR; mass resolving power improves linearly, while mass accuracy and dynamic range improve quadratically with magnetic field strength. Here, MALDI MSI at 21T is demonstrated for the first time: mass resolving power in excess of 1 600 000 (at m/z 400), root-mean-square mass measurement accuracy below 100 ppb, and dynamic range per pixel over 500:1 were obtained from the direct analysis of biological tissue sections. Molecular features with m/z differences as small as 1.79 mDa were resolved and identified with high mass accuracy. These features allow for the separation and identification of lipids to the underlying structures of tissues. The unique molecular detail, accuracy, sensitivity, and dynamic range combined in a 21T MALDI FT-ICR MSI experiment enable researchers to visualize molecular structures in complex tissues that have remained hidden until now. The instrument described allows for future innovative, such as high-end studies to unravel the complexity of biological, geological, and engineered organic material surfaces with an unsurpassed detail.
Veterinary medicine has undergone sweeping changes in the last few decades. Women now account for 55 percent of the active veterinarians in the field, and nearly 80 percent of veterinary students are ...women. However, average salaries have dropped as this shift has occurred, and even with women in the vast majority, only 25 percent of leadership roles are held by women. These trends point to gender-based inequality that veterinary medicine, a profession that tilts so heavily toward women, is struggling to address. How will the profession respond? What will this mean for our students and schools? What will it mean for our pets entrusted to veterinarian care? Who has succeeded in these situations? Who is taking action to lead change? What can we learn from them to lead the pack in our lives? Leaders of the Pack, by Julie Kumble and Dr. Donald Smith, explores key themes in leadership and highlights women in veterinary medicine whose stories embody those themes. In it, Kumble and Smith cull over three years of interviews to profile a wide variety of women as they share triumphs and challenges, lucky as well as tough breaks, and the sound advice and words that inspired them to take their careers in unanticipated directions. By sharing unique stories that illuminate different paths to leadership and reflecting on best practices through commentary and research, Leaders of the Pack will allow more female leaders to create wider pathways to the top of their profession.
High magnetic field Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry provides the highest mass resolving power and mass measurement accuracy for detailed characterization of ...complex chemical mixtures. Here, we report the coupling of online liquid chromatography of complex mixtures with a 21 tesla FT-ICR mass spectrometer. The high magnetic field enables large ion populations to be analyzed for each spectrum for a high dynamic range, with 3.2 million mass resolving power at m/z 400 (6.2 s transient duration) or 1.6 million (3.1 s transient duration) while maintaining high mass accuracy for molecular formula assignment (root-mean-square assignment error < 0.150 ppm). Thousands of unique elemental compositions are assigned per mass spectrum, which can be grouped by the heteroatom class, double bond equivalents (the number of rings and double bonds to carbon), and carbon number. Figures of merit are discussed, as well as characterization of an Arabian heavy vacuum gas oil in terms of the ring number, compound class, double bond equivalents, and ion type. Consideration of elemental composition and retention order provides additional structural information.
The Age of Westerlund 1 Revisited Beasor, Emma R.; Davies, Ben; Smith, Nathan ...
Astrophysical journal/The Astrophysical journal,
05/2021, Letnik:
912, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract
The cluster Westerlund 1 (Wd1) is host to a large variety of post-main-sequence (MS) massive stars. The simultaneous presence of these stars can only be explained by stellar models if the ...cluster has a finely tuned age of 4–5 Myr, with several published studies independently claiming ages within this range. At this age, stellar models predict that the cool supergiants (CSGs) should have luminosities of
log
(
L
/
L
⊙
)
≈
5.5
, close to the empirical luminosity limit. Here, we test that prediction using archival data and new photometry from Stratospheric Observatory for Infrared Astronomy to estimate bolometric luminosities for the CSGs. We find that these stars are on average 0.4 dex too faint to be 5 Myr old, regardless of which stellar evolutionary model is used, and instead are indicative of a much older age of
10.4
−
1.2
+
1.3
Myr. We argue that neither systematic uncertainties in the extinction law nor stellar variability can explain this discrepancy. In reviewing various independent age estimates of Wd1 in the literature, we first show that those based on stellar diversity are unreliable. Second, we reanalyze Wd1's pre-MS stars employing the Damineli extinction law, finding an age of
7.2
−
2.3
+
1.1
Myr; older than that of previous studies, but which is vulnerable to systematic errors that could push the age close to 10 Myr. However, there remains significant tension between the CSG age and that inferred from the eclipsing binary W13. We conclude that stellar evolutionary models cannot explain Wd1 under the single-age paradigm. Instead, we propose that the stars in the Wd1 region formed over a period of several megayears.
Positron emission tomography (PET) provides a means of studying physiological and pharmacological processes as they occur in the living brain. Mice, rats, dogs, cats, pigs and non-human primates are ...often used in studies using PET. They are commonly anaesthetized with ketamine, propofol or isoflurane in order to prevent them from moving during the imaging procedure. The use of anaesthesia in PET studies suffers, however, from the drawback of possibly altering central neuromolecular mechanisms. As a result, PET findings obtained in anaesthetized animals may fail to correctly represent normal properties of the awake brain. Here, we review findings of PET studies carried out either in both awake and anaesthetized animals or in animals given at least two different anaesthetics. Such studies provide a means of estimating the extent to which anaesthesia affects the outcome of PET neuroimaging in animals. While no final conclusion can be drawn concerning the ‘best’ general anaesthetic for PET neuroimaging in laboratory animals, such studies provide findings that can enhance an understanding of neurobiological mechanisms in the living brain.
Insulin receptor signalling has a central role in mammalian biology, regulating cellular metabolism, growth, division, differentiation and survival. Insulin resistance contributes to the pathogenesis ...of type 2 diabetes mellitus and the onset of Alzheimer's disease; aberrant signalling occurs in diverse cancers, exacerbated by cross-talk with the homologous type 1 insulin-like growth factor receptor (IGF1R). Despite more than three decades of investigation, the three-dimensional structure of the insulin-insulin receptor complex has proved elusive, confounded by the complexity of producing the receptor protein. Here we present the first view, to our knowledge, of the interaction of insulin with its primary binding site on the insulin receptor, on the basis of four crystal structures of insulin bound to truncated insulin receptor constructs. The direct interaction of insulin with the first leucine-rich-repeat domain (L1) of insulin receptor is seen to be sparse, the hormone instead engaging the insulin receptor carboxy-terminal α-chain (αCT) segment, which is itself remodelled on the face of L1 upon insulin binding. Contact between insulin and L1 is restricted to insulin B-chain residues. The αCT segment displaces the B-chain C-terminal β-strand away from the hormone core, revealing the mechanism of a long-proposed conformational switch in insulin upon receptor engagement. This mode of hormone-receptor recognition is novel within the broader family of receptor tyrosine kinases. We support these findings by photo-crosslinking data that place the suggested interactions into the context of the holoreceptor and by isothermal titration calorimetry data that dissect the hormone-insulin receptor interface. Together, our findings provide an explanation for a wealth of biochemical data from the insulin receptor and IGF1R systems relevant to the design of therapeutic insulin analogues.
A recently developed extrography separation method fractionates petroleum asphaltenes based on their ionization efficiency, which correlates with polarity, aggregation tendency, and asphaltene ...structure (single-core or island versus multicore or archipelago). Archipelago asphaltenes were recently demonstrated to coexist with island structures in a variety of petroleum samples; however, archipelago compounds ionize much less efficiently than island compounds, making the former difficult to observe by mass spectrometry without prior separation. Highly processed coal-derived asphaltenes have been studied previously to reveal only small, single-core structure asphaltenes; however, the structure(s) of asphaltenes from unaltered coal extracts has not been extensively studied. Thus, this work focuses on the application of the extrography separation to an unaltered Illinois coal No. 6 asphaltene extract to reveal the coexistence of island and archipelago structural motifs by positive-ion (+) atmospheric pressure photoionization (APPI) Fourier transform ion cyclotron resonance mass spectrometry. Asphaltenes from a Wyoming crude oil sample are also characterized for comparison with coal asphaltenes. The results reveal that Wyoming crude oil asphaltenes contain mainly island species, whereas coal asphaltenes contain archipelago and island compounds with high oxygen content. The structural analysis is enabled by a new “multinotch” stored-waveform inverse Fourier transform isolation, which selectively isolates high-aromaticity precursor ions at each of several nominal mass ranges prior to fragmentation by infrared multiphoton dissociation, and enables unambiguous determination of island versus archipelago species in samples that contain compounds with high and low aromaticity. The more polarizable fractions from each asphaltene sample reveal low-aromaticity polyfunctional oxygenated species, with a solubility behavior consistent with asphaltenes but a compositional range typical of maltenes. These atypical asphaltene species, which ionize poorly, are hypothesized to participate in multiple hydrogen bonding interactions and thus exhibit strong adsorption on polar stationary phases such as SiO2. Furthermore, these polarizable polyfunctional species ionize preferentially as protonated cations by (+) APPI, accounting for their capability to hydrogen-bond in solution. Collectively, the results demonstrate the existence of archipelago structures in both coal and petroleum asphaltenes, along with polyoxygenated species with low aromaticity that behave like asphaltenes in terms of solubility, because they can establish stronger intermolecular forces such as hydrogen bonding.
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