Heme Binding and Transfer in the Isd Heme Scavenging Pathway of Staphylococcus aureus

The antibiotic resistant bacterium Staphylococcus aureus is a significant problem in hospitals and communities worldwide. Survival of the bacterium in the host is reliant on iron scavenging. Staphylococcus aureus has adopted specialized mechanisms for scavenging iron from the host. The cell wall and membrane-associated iron regulated surface determinant (Isd) proteins allow Staphylococcus aureus to scavenge iron from the heme in hemoglobin. There are nine Isd proteins (IsdH, IsdB, IsdA, IsdC, IsdE, IsdD, IsdF, IsdG and IsdI) located at different depths in the cell wall and membrane. Magnetic circular dichroism (MCD) spectroscopy and electrospray ionization mass spectrometry (ESI-MS) have been used to determine the direction, mechanistic details and heme binding ligands of the Isd heme transfer system. Ferric heme extracted from metHb by IsdB and has been demonstrated to transfer in a unidirectional fashion with the heme transferring along the pathway in the sequence (proximal amino acid) IsdB-N2 (Tyr) -\u3e IsdA-N (Tyr) -\u3e IsdC-N (Tyr) -\u3e IsdE (His) or, alternatively, when initiating from IsdH-N3 (Tyr) the transfer sequence is -\u3e IsdA-N (Tyr) -\u3e IsdC-N (Tyr) -\u3e IsdE (His). Heme transfer through the cell wall must occur through IsdC indicating that IsdC acts as the central conduit of the Isd system. MCD and ESI-MS data show that disruption of unidirectional heme transfer occurs with heme analogs and protein mutational studies. Finally kinetic analysis provides rate constants for the major unidirectional reaction steps

Age-dependent mating tactics in male bushbuck (Tragelaphus scriptus)

Intra-specific variation in mating behaviour has been described for a number of taxa including arthropods, fishes, amphibians, reptiles, birds and mammals. Several mechanisms have been proposed to explain the various mating behavioural variations observed in mammals. For example, an individual’s behaviour may be constrained by its condition or status (making-the- best of-a-bad-job strategy) or an alternative phenotype may be maintained by frequency-dependent selection influencing a genetic polymorphism (alternative strategies). In the majority of ungulates, variation in mating tactics is most likely maintained as a conditional strategy influenced by multiple internal factors like age, health or body size, as well as external factors such as population density, number of competitors and social dominance rank. In the present study, we investigated male mating tactics in a cryptic, bush-dwelling antelope from tropical Africa, the bushbuck, Tragelaphus scriptus (Figures.1, 2). Different mating strategies are expected to emerge, if variation in mating tactic is maintained as a conditional strategy influenced by age and / or body size: 1) Defending a territory when old and strong, what allows the owner to associating more frequently with females within the combined territory and home-range area. 2) No territory defence when young and weak, thereby associating with females less frequently and therefore sneak-mating with them

Strained Silicon Complementary TFET SRAM: Experimental Demonstration and Simulations

A half SRAM cell with strained Si nanowire complementary tunnel-FETs (TFETs) was fabricated and characterized to explore the feasibility and functionality of 6T-SRAM based on TFETs. Outward-faced n-TFETs are used as access-transistors. Static measurements were performed to determine the SRAM butterfly curves, allowing the assessment of cell functionality and stability. The forward p-i-n leakage of the access-transistor at certain bias configurations leads to malfunctioning storage operation, even without the contribution of the ambipolar behavior. At large VDD, lowering of the bit-line bias is needed to mitigate such effect, demonstrating functional hold, read and write operations. Circuit simulations were carried out using a Verilog-A compact model calibrated on the experimental TFETs, providing a better understanding of the TFET SRAM operation at different supply voltages and for different cell sizing and giving an estimate of the dynamic performance of the cell

Photoionization of (H 2

Photoionizationof (H{sub 2}){sub 2} and clusters of O{sub 2} are investigated in a molecular beam experiment. No evidence was found for the existence of stable (H{sub 2}){sub 2}{sup +}. Photoionization spectra of (H{sub 2}){sub 2}+h{nu}{yields} {yields} H{sub 3}{sup +} + H + e is quite similar to that of H{sup 2} +h{nu} {yields} H{sub 2}{sup +} + e, yet the appreciable differences in some features of spectra suggests that there is a competition between the autoionization and vibrational predissociation of vibronically excited (H{sub 2}){sub 2}. From the photoionization thresholds of (O{sub 2}){sub n}, n = 1-5, it is concluded that (O{sub 2}){sub 2}{sup +} is bound by 0.26 ± 0.02 eV, but the additional binding energies for higher clusters of O{sub 2}{sup +} are much smaller; just about what one would expect from a charge induced dipole interaction

Investigating harbor porpoise (Phocoena phocoena) population differentiation using RAD-tag genotyping by sequencing

The population status of the harbor porpoise ( Phocoena phocoena ) in the Baltic Sea and adjacent regions is still not fully resolved. Here, we present a pilot study using the double digest restriction-site associated DNA sequencing (ddRAD-seq) genotyping- by -sequencing method on specimens from the Baltic Sea, eastern North Sea, Spain and the Black Sea. From a single Illumina lane and a set of 49 individuals, w e obtained around 6000 SNPs. We used these markers to estimate population structure and differentiation, and identified splits between porpoises from the North Sea and the Baltic, and within regions in the Baltic Sea (between the Belt Sea and the Inner Baltic Sea). The SNP analysis confirms population structure elucidated by previous mtDNA/microsatellite studies. We demonstrate the feasibility of SNP analysis on opportunistically sampled cetacean samples, with varying DNA quality, for population diversity and divergence analysis

Correction of joint angles from kinect for balance exercising and assessment

[EN] The new generation of videogame interfaces such as Microsoft's Kinect opens the possibility of implementing exercise programs for physical training, and of evaluating and reducing the risks of elderly people falling. However, applications such as these might require measurements of joint kinematics that are more robust and accurate than the standard output given by the available middleware. This article presents a method based on particle filters for calculating joint angles from the positions of the anatomical points detected by PrimeSense's NITE software. The application of this method to the measurement of lower limb kinematics reduced the error by one order of magnitude, to less than 10 degrees, except for hip axial rotation, and it was advantageous over inverse kinematic analysis, in ensuring a robust and smooth solution without singularities, when the limbs are out-stretched and anatomical landmarks are aligned.This work has been undertaken within the framework of the iStoppFalls project, which has received funding from the European Community (grant agreement FP7-ICT-2011-7-287361) and the Australian Government.De Rosario Martínez, H.; Belda Lois, JM.; Fos Ros, F.; Medina Ripoll, E.; Poveda Puente, R.; Kroll, M. (2014). Correction of joint angles from kinect for balance exercising and assessment. Journal of Applied Biomechanics. 30(2):294-299. https://doi.org/10.1123/jab.2013-0062S29429930