Probing the structure-function relationship of hemoglobin in living human red blood cells

Hemoglobin (Hb) is a key component of respiratory system and as such plays important role in human physiology. The studies of Hb's structure and functions are usually performed on cell-free protein; however, it has been shown that there are functionally relevant differences between isolated Hb and Hb present inside red blood cells (RBCs). It is clear that new experimental approaches are needed to understand the origin of these differences and to gain insight into the structure-function relationship of Hb within intact living cells. In this work we present a novel application of Resonance Raman spectroscopy to study heme active site of different forms of human Hb within living RBCs using laser excitation lines in resonance with their Soret absorption bands. These studies revealed that there are no significant changes in the disposition of the Fe-O-O fragment or the Fe-NHis linkage for Hb molecules enclosed in RBCs and these in free isolated states. However, some changes in the orientation of the heme vinyl groups were observed which might account for the differences in the protein activity and ligand affinity. This work highlights importance of protein-based studies and presents a new opportunity to translate these results to physiological cell systems

Surface Potential Driven Water Harvesting from Fog.

Access to clean water is a global challenge, and fog collectors are a promising solution. Polycarbonate (PC) fibers have been used in fog collectors but with limited efficiency. In this study, we show that controlling voltage polarity and humidity during the electrospinning of PC fibers improves their surface properties for water collection capability. We experimentally measured the effect of both the surface morphology and the chemistry of PC fiber on their surface potential and mechanical properties in relation to the water collection efficiency from fog. PC fibers produced at high humidity and with negative voltage polarity show a superior water collection rate combined with the highest tensile strength. We proved that electric potential on surface and morphology are crucial, as often designed by nature, for enhancing the water collection capabilities via the single-step production of fibers without any postprocessing needs

What are the career implications of ‘seeing eye to eye’? Examining the role of leader-member exchange (LMX) agreement on employability and career outcomes

Are there career benefits to leaders and followers agreeing about the quality of their leader‐member exchange (LMX) relationship? Is LMX disagreement always detrimental for a follower's career? Can the examination of LMX agreement as a substantive variable help us cast new light on some of the inconclusive findings of past research on LMX and career outcomes? These questions motivate our research. Using theories of social exchange and sponsorship, and responses from 967 leader–follower dyads of Information and Communication Technology (ICT) professionals in seven European countries, we examined the role of LMX agreement on subjective and objective career outcomes. After conducting polynomial regression combined with response surface analysis, we found that both follower‐rated and leader‐rated employability were higher when the leader agreed with the follower at a high level of LMX (versus a low level of LMX). In case of disagreement, strong support was found for leader‐rated employability being higher when the leader's perceptions of LMX exceeded those of their follower. Furthermore, follower‐rated employability was found to mediate the relationship between LMX (dis)agreement and perceived career success, promotions, salary, and bonuses. Support was also found for the mediating role of leader‐rated employability in the case of perceived career success, promotions, and salary but not for bonuses. Our findings highlight the importance of LMX (dis)agreement for career outcomes and further point to the possibility of employability offering an alternative explanation for the mixed findings of past LMX‐career research

Surface potential and roughness controlled cell adhesion and collagen formation in electrospun PCL fibers for bone regeneration

Surface potential of biomaterials is a key factor regulating cell responses, driving their adhesion and signaling in tissue regeneration. In this study we compared the surface and zeta potential of smooth and porous electrospun polycaprolactone (PCL) fibers, as well as PCL films, to evaluate their significance in bone regeneration. The ' surface potential of the fibers was controlled by applying positive and negative voltage polarities during the electrospinning. The surface properties of the different PCL fibers and films were measured using X-ray photoelectron spectroscopy (XPS) and Kelvin probe force microscopy (KPFM), and the zeta potential was measured using the electrokinetic technique. The effect of surface potential on the morphology of bone cells was examined using advanced microcopy, including 3D reconstruction based on a scanning electron microscope with a focused ion beam (FIB-SEM). Initial cell adhesion and collagen formation were studied using fluorescence microscopy and Sirius Red assay respectively, while calcium mineralization was confirmed with energy-dispersive x-ray (EDX) and Alzarin Red staining. These studies revealed that cell adhesion is driven by both the surface potential and morphology of PCL fibers. Furthermore, the ability to tune the surface potential of electrospun PCL scaffolds provides an essential electrostatic handle to enhance cell-material interaction and cellular activity, leading to controllable morphological changes

Temperature Effects Explain Continental Scale Distribution of Cyanobacterial Toxins

Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect effects of temperature were the main drivers of the spatial distribution in the toxins produced by the cyanobacterial community, the toxin concentrations and toxin quota. Generalized linear models showed that a Toxin Diversity Index (TDI) increased with latitude, while it decreased with water stability. Increases in TDI were explained through a significant increase in toxin variants such as MC-YR, anatoxin and cylindrospermopsin, accompanied by a decreasing presence of MC-LR. While global warming continues, the direct and indirect effects of increased lake temperatures will drive changes in the distribution of cyanobacterial toxins in Europe, potentially promoting selection of a few highly toxic species or strains.Peer reviewe

Bound water freezing in Antarctic Umbilicaria aprina from Schirmacher Oasis

The effect of low temperature on Umbilicaria aprina collected from Schirmacher Oasis, East Antarctica, was determined over a wide range of hydration using proton free induction decays, proton nuclear magnetic resonance (NMR) spectra and differential scanning calorimetry methods. The proton NMR line is a superposition of the broad component from the solid matrix of the thallus and a narrower component from the averaged bound water pool. Proton free induction decays may be resolved into three components: a solid component well described by the Abragam function and two exponentially decaying components from water loosely bound and water tightly bound in the thallus. With decreased temperature the loosely bound water pool (freezing water) is transferred to the tightly bound water pool (non-freezing water), and vanishes below -40°C. Bound water freezing and melting temperatures decrease with the decrease of hydration level, suggesting that heterogeneous ice nucleation is responsible for water freezing. The onset of bound water freezing temperature is c. 10°C lower than the melting temperature. The U. aprina thalli do not reveal the ability to stimulated ice nucleation at higher temperature. Freeze-thaw cycles showed that for n > 5 cycles no substantial change occurs in the difference between melting and freezing temperatures