Genetic and Morphometric Evidence for the Conspecific Status of the Bumble Bees, Bombus melanopygus and Bombus edwardsii

The taxonomic status of closely related bumble bee species is often unclear. The relationship between the two nominate taxa, Bombus melanopygus Nylander (Hymenoptera: Apidae) and Bombus edwardsii Cresson (Hymenoptera: Apidae), was investigated using genetic (enzyme electrophoretic) and morphometric analyses. The taxa differ in the color of the abdominal terga two and three, being ferruginous in B. melanopygus and black in B. edwardsii. B. edwardsii occurs throughout California, while B. melanopygus extends north through Oregon, to Alaska and Canada. They are sympatric only in southern Oregon and northern California. The taxonomic status of these taxa was questioned when Owen and Plowright (1980) reared colonies from queens collected in the area of sympatry, and discovered that pile coloration was due to a single, biallelic Mendelian gene, with the red (R) allele dominant to the black (r). Here it is shown that all the taxa, whether from California, Oregon, or Alberta, have the same electrophoretic profile and cannot be reliably distinguished by wing morphometrics. This strongly supports the conclusion that B. melanopygus and B. edwardsii are conspecific and should be synonymized under the name B. melanopygus. Hence, there is a gene frequency cline running from north to south, where the red allele is completely replaced by the black allele over a distance of about 600 km

Determination of X-ray flux using silicon pin diodes

Accurate measurement of photon flux from an X-ray source is a parameter required to calculate the dose absorbed by a sample. The development of a model for determining the photon flux incident on pin diodes, and experiments to test this model, are described for incident energies between 4 and 18 keV used in macromolecular crystallography

Serial synchrotron and XFEL crystallography for studies of metalloprotein catalysis

Research into the earliest development of inhibitory control is limited by a lack of suitable tasks. In particular, commonly used inhibitory control tasks frequently have too high language and working memory demands for children under 3 years of age. Furthermore, researchers currently tend to shift to a new set of inhibitory control tasks between infancy, toddlerhood, and early childhood, raising doubts about whether the same function is being measured. Tasks that are structurally equivalent across age could potentially help resolve this issue. In the current report, a new response inhibition task, the Early Childhood Inhibitory Touchscreen Task (ECITT), was developed. This task can be minimally modified to suit different ages, whilst remaining structurally equivalent. In the new task, participants have to overcome a tendency to respond to a frequently rewarded location on a touchscreen and instead make an alternative response. The ECITT was validated in three independent studies (with additional data, N = 166, reported in Supporting Information). In Study 1 (N = 81), cross-sectional data indicated that inhibitory performance on the task improved significantly between 24 and 30 months of age. In Study 2 (N = 38), longitudinal data indicated steady improvement in inhibitory control between 18, 21 and 24 months, with significant stability in individual performance differences between each consecutive age in terms of accuracy (but not in terms of reaction time). Finally, in Study 3 (N = 64), inhibitory performance on a faster-paced version of the same task showed a similar developmental course across the lifespan (4–84 years) to other response inhibition tasks and was significantly correlated with Stop-signal performance. The ECITT extends the assessment of response inhibition earlier than previous tasks–into early toddlerhood. Because the task is simple and structurally equivalent across age, future longitudinal studies should benefit from using the ECITT to investigate the development of inhibitory control in a consistent manner across the toddler years and beyond

The effect of irradiation-induced disorder on the conductivity and critical temperature of the organic superconductor κ\kappa-(BEDT-TTF)2_2Cu(SCN)2_2

We have introduced defects into clean samples of the organic superconductor $\kappa$-(BEDT-TTF)$_2$Cu(SCN)$_2$ in order to determine their effect on the temperature dependence of the conductivity and the critical temperature $T_{\rm c}$. We find a violation of Matthiessen's rule that can be explained by a model of the conductivity involving a defect-assisted interlayer channel which acts in parallel with the band-like conductivity. We observe an unusual dependence of $T_{\rm c}$ on residual resistivity which is not consistent with the generalised Abrikosov-Gor'kov theory for an order parameter with a single component, providing an important constraint on models of the superconductivity in this material

A new on-axis multimode spectrometer for the macromolecular crystallography beamlines of the Swiss Light Source

Complementary techniques greatly aid the interpretation of macromolecule structures to yield functional information, and can also help to track radiation-induced changes. A new on-axis spectrometer being integrated into the macromolecular crystallography beamlines of the Swiss Light Source is presented

Variability in X-ray induced effects in [Rh(COD)Cl]₂ with changing experimental parameters

X-ray characterisation methods have undoubtedly enabled cutting-edge advances in all aspects of materials research. Despite the enormous breadth of information that can be extracted from these techniques, the challenge of radiation-induced sample change and damage remains prevalent. This is largely due to the emergence of modern, high-intensity X-ray source technologies and the growing potential to carry out more complex, longer duration in situ or in operando studies. The tunability of synchrotron beamlines enables the routine application of photon energy-dependent experiments. This work explores the structural stability of [Rh(COD)Cl]2, a widely used catalyst and precursor in the chemical industry, across a range of beamline parameters that target X-ray energies of 8 keV, 15 keV, 18 keV and 25 keV, on a powder X-ray diffraction synchrotron beamline at room temperature. Structural changes are discussed with respect to absorbed X-ray dose at each experimental setting associated with the respective photon energy. In addition, the X-ray radiation hardness of the catalyst is discussed, by utilising the diffraction data collected at the different energies to determine a dose limit, which is often considered in protein crystallography and typically overlooked in small molecule crystallography. This work not only gives fundamental insight into how damage manifests in this organometallic catalyst, but will encourage careful consideration of experimental X-ray parameters before conducting diffraction on similar radiation-sensitive organometallic materials

Automated eukaryotic gene structure annotation using EVidenceModeler and the Program to Assemble Spliced Alignments

EVidenceModeler (EVM) is an automated annotation tool that predicts protein-coding regions, alternatively spliced transcripts and untranslated regions of eukaryotic genes

Revealing low-dose radiation damage using single-crystal spectroscopy

Data on the rapid reduction of haem proteins in the X-ray beam at synchrotron sources are presented. The use of single-crystal spectroscopy to detect these changes and their implication for diffraction data collection from oxidized species is also discussed

Aspartate or arginine? Validated redox state X-ray structures elucidate mechanistic subtleties of FeIV = O formation in bacterial dye-decolorizing peroxidases

Structure determination of proteins and enzymes by X-ray crystallography remains the most widely used approach to complement functional and mechanistic studies. Capturing the structures of intact redox states in metalloenzymes is critical for assigning the chemistry carried out by the metal in the catalytic cycle. Unfortunately, X-rays interact with protein crystals to generate solvated photoelectrons that can reduce redox active metals and hence change the coordination geometry and the coupled protein structure. Approaches to mitigate such site-specific radiation damage continue to be developed, but nevertheless application of such approaches to metalloenzymes in combination with mechanistic studies are often overlooked. In this review, we summarize our recent structural and kinetic studies on a set of three heme peroxidases found in the bacterium Streptomyces lividans that each belong to the dye decolourizing peroxidase (DyP) superfamily. Kinetically, each of these DyPs has a distinct reactivity with hydrogen peroxide. Through a combination of low dose synchrotron X-ray crystallography and zero dose serial femtosecond X-ray crystallography using an X-ray free electron laser (XFEL), high-resolution structures with unambiguous redox state assignment of the ferric and ferryl (FeIV = O) heme species have been obtained. Experiments using stopped-flow kinetics, solvent-isotope exchange and site-directed mutagenesis with this set of redox state validated DyP structures have provided the first comprehensive kinetic and structural framework for how DyPs can modulate their distal heme pocket Asp/Arg dyad to use either the Asp or the Arg to facilitate proton transfer and rate enhancement of peroxide heterolysis