Combined High-Speed Single Particle Tracking of Membrane Proteins and Super-resolution of Membrane-Associated Structures

Many experiments have shown that the diffusive motion of lipids and membrane proteins are slower on the cell surface than those in artificial lipid bilayers or blebs. One hypothesis that may partially explain this mystery is the effect of the cytoskeleton structures on the protein dynamics. A model proposed by Kusumi [1] is the Fence-Picket Model which describes the cell membrane as a set of compartment regions, each ~ 10 to 200 nm in size, created by direct or indirect interaction of lipids and proteins with actin filaments just below the membrane. To test this hypothesis, we have assembled a high-speed single particle tracking microscope and use a hybrid tracking and super-resolution approach on the same cell. We labeled the high-affinity FceRI receptor in Rat Basophilic Leukemia (RBL) cells and tracked these transmembrane proteins at up to 1000 frames per second. The cells were fixed immediately after tracking and further labeled for super-resolution imaging of actin filaments and other membrane-associated components were collected. For best correlation of tracking and super-resolution, we refined a fixation protocol to prevent morphology changes during the fixation process that often go unnoticed. Bright field images allow re-alignment of cell with about ~ 10 nm precision. This sequential approach allows use of far-red dyes for tracking and super-resolution, ameliorating chromatic aberrations. We will present the results of this high-speed tracking within the context of actin and other membrane associated proteins imaged with ~ 20 nm resolution. [1].Ritchie, K.; Iino, R.; Fujiwara, T.; Murase, K.; Kusumi, A. The fence and picket structure of the plasma membrane of live cells as revealed by single molecule techniques (Review). Mol. Membr. Biol. 2003, 20, 13−18

The Commodities Fetish? Financialisation and Finance Capital in the US Oil Industry

This is the author accepted manuscript. The final version is available from Brill via the DOI in this recordThis article explores the financialisation of the world's most important commodity, oil. It argues that much of the literature on the financialisation of commodities tends to adopt a dualistic approach to financial markets and physical producers, where financial and non-financial activities are assumed to be externally-related and counterposed to one another. The article locates the roots of this analytical separation in a mistaken acceptance of the fetish character of interest-bearing capital (IBC) - a view that the exchange of loanable sums of capital represents a relationship between money-capitalists rather than a relationship to the moment of production. Against such dichotomous readings, the article argues that the financialisation of oil needs to be understood as part of the reworking of ownership and control across the oil commodity circuit, expressed through the combined centralisation and concentration of capital over the money, productive and commercial moments. This argument is demonstrated through an original empirical investigation of the US oil industry, including 20 years of weekly trading data on the New York Mercantile Exchange (NYMEX) and a detailed study of more than 160 oil and energy-related firms in the US. By mapping the structural weight and connections between different capitalist actors involved in accumulation across the oil sector, we gain a better understanding of the ultimate dynamics (and beneficiaries) of the carbon economy

Sustaining Participant Involvement in Crowdsourcing Contests through Collaboration

With the advances in internet technologies and the emergence of crowdsourcing, organizations are now increasingly looking outside their boundaries for solving problems. Yet, the success of crowdsourcing processes depends on the sustained participation of crowdsourcing individuals. Previous studies have mainly focused on understanding individuals’ initial motivation for participation with few focusing on the factors that affect individuals’ sustained participation in crowdsourcing contests. None of these studies examined how collaboration affects individuals’ participation behavior in crowdsourcing contests. This study attempts to understand how individuals’ collaboration (in the form of comments and votes) affects their sustained participation in online problem solving contests. This study uses data from the Kaggle website that holds online data science competitions in which individuals submit their proposed solutions with the best solutions being rewarded. Our results show that individuals who receive more attention from other members tend to come back and maintain their participation in the platform

Passivating effect of ternary alloyed AgZnSe shell layer on the structural and luminescent properties of CdS quantum dots

The surface passivation of luminescent CdS quantum dots (QDs) via epitaxial overgrowth of new alloyed ternary AgZnSe shell layer is reported here. Two synthetic fabrication strategies were used to tune the optical properties of CdS/AgZnSe core/alloyed shell QDs across the visible region. Transmission electron microscopy, powder X-ray diffraction, Raman, UV/vis and fluorescence spectrophotometric techniques were used to characterize the nanocrystals. Analysis of the internal structure of the QDs revealed that homogeneity of the particle reduced as the size increased, thus indicating that the QDs growth transitioned from an interfacial epitaxial homogenous state to a heterogeneous state. The crystal structure of the QDs revealed a distinct zinc-blende diffraction pattern for CdS while CdS/AgZnSe core/alloyed shell QDs kinetically favoured a phase change process from the zinc-blende phase to a wurtzite phase. Analysis of the photophysical properties revealed varying degrees of interfacial defect state suppression in CdS/AgZnSe QDs which was dependent on the QDs size. Specifically, the fluorescence quantum yield (QY) of CdS/AgZnSe QDs was at most ~5-fold higher than the CdS core and varied from 35% to 73%. We found that band gap modulation via the synthetic fabrication strategy employed, influenced the optical properties of the core/alloyed shell QDs. The CdS/AgZnSe QDs produced in this work hold great promise in light-emitting optoelectronic applications.The Water Research Council (WRC) project K5/2752, South Africa and the University of Pretoria.http://www.elsevier.com/locate/mssphj2020Chemistr

Pandemic effects: COVID-19 and the crisis of development in the Middle East

This is the final version. Available from Wiley via the DOI in this record. This article explores the effects of the COVID-19 pandemic on socio-economic development and political mobilization in the Middle East. It argues that beyond its direct public health implications, the pandemic is serving to intensify the extreme differences in wealth and power that have characterized the region for many years. The article gives an overview of the region's political economy prior to the pandemic, examining the legacies of the 2011 uprisings and the ways in which notions of 'crisis' were mobilized to re-embed market-led development models over the last decade. Within this broader context, it maps the generalized deterioration in living conditions that has occurred since mid-2020. Following this, it discusses the pandemic's exacerbation of regional unevenness, exploring the strengthened position of more powerful states, notably Israel and the Gulf states, within the political and economic hierarchies of the Middle East. Finally, the article takes a closer look at Lebanon, Tunisia and Sudan, three countries that have been sharply hit by the pandemic, but that were also marked by substantial mass protests and political mobilization immediately prior to 2020. These countries illustrate the political complexities involved in situations where a profound socio-economic crisis intersects with a long-standing erosion of political hegemony.British Academ

Decoration of nanovesicles with pH (low) insertion peptide (pHLIP) for targeted delivery

Acidity at surface of cancer cells is a hallmark of tumor microenvironments, which does not depend on tumor perfusion, thus it may serve as a general biomarker for targeting tumor cells. We used the pH (low) insertion peptide (pHLIP) for decoration of liposomes and niosomes. pHLIP senses pH at the surface of cancer cells and inserts into the membrane of targeted cells, and brings nanomaterial to close proximity of cellular membrane. DMPC liposomes and Tween 20 or Span 20 niosomes with and without pHLIP in their coating were fully characterized in order to obtain fundamental understanding on nanocarrier features and facilitate the rational design of acidity sensitive nanovectors. The samples stability over time and in presence of serum was demonstrated. The size, ζ-potential, and morphology of nanovectors, as well as their ability to entrap a hydrophilic probe and modulate its release were investigated. pHLIP decorated vesicles could be useful to obtain a prolonged (modified) release of biological active substances for targeting tumors and other acidic diseased tissues

Fine and hyperfine resolved empirical energy levels of VO

A MARVEL (measured active rotational-vibrational energy levels) analysis of the spectra of vanadium oxide (VO) is performed, involving thirteen electronic states (6 quartets and 7 doublets). VO data from 14 sources are used to form three networks: hyperfine-resolved quartets, hyperfine-unresolved quartets and hyperfine-unresolved doublets. A single quartet network is formed by deperturbing the hyperfine lines and 191 lines are assigned to an intercombination 2 –X band system in the visible region previously recorded by Hopkins et al. (J. Chem. Phys. 130 (2009) 144308), allowing the doublet and quartet networks to be merged. As a result 6 603/4 402 validated transitions/final energies were obtained from analysis of the hyperfine-resolved network and 9 087/4 712 from the unresolved. energy values and other molecular constants are determined for all doublet states within the networks

Liquid-liquid displacement in slippery liquid-infused membranes (SLIMs)

Liquid-infused membranes inspired by slippery liquid-infused porous surfaces (SLIPS) have been recently introduced to membrane technology. The gating mechanism of these membranes is expected to give rise to anti-fouling properties and multi-phase transport capabilities. However, the long-term retention of the infusion liquid has not yet been explored. To address this issue, we investigate the retention of the infusion liquid in slippery liquid-infused membranes (SLIMs) via liquid-liquid displacement porometry (LLDP) experiments combined with microscopic observations of the displacement mechanism. Our results reveal that pores will be opened corresponding to the capillary pressure, leading to preferential flow pathways for water transport. The LLDP results further suggest the presence of liquid-lined pores in SLIM. This hypothesis is analyzed theoretically using an interfacial pore flow model. We find that the displacement patterns correspond to capillary fingering in immiscible displacement in porous media. The related physics regarding two-phase flow in porous media is used to confirm the permeation mechanism appearing in SLIMs. In order to experimentally observe liquid-liquid displacement, a microfluidic chip mimicking a porous medium is designed and a highly ramified structure with trapped infusion liquid is observed. The remaining infusion liquid is retained as pools, bridges and thin films around pillar structures in the chip, which further confirms liquid-lining. Fractal dimension analysis, along with evaluation of the fluid (non-wetting phase) saturation, further confirms that the fractal patterns correspond to capillary fingering, which is consistent with an invasion percolation with trapping (IPT) model

Chemo-enzymatic saccharification strategy of microalgae chlorella sorokiniana

Biofuel production using microalgae attracted much attention because it can be cultured using CO2 and sunlight. With high carbohydrate content, microalgae have the potential to be used as a fermentation feedstock for bioethanol production. In present work, chemo-enzymatic saccharification of Chlorella sorokiniana microalgae were investigated. Chemical hydrolysis of the biomass followed by enzymatic hydrolysis and was also evaluated the effect of combining the two enzymes and the sequential addition. The effect of α-amylase concentrations was analyzed in ranged between 50 and 8000 U/g of biomass and for amyloglucosidase between 90 and 600 U/g of biomass. The higher concentrations showed the highest conversion of reducing sugars. The α-amylase concentration 8000 U/g of biomass presented a conversion of 43.06 ± 2.92% (w/w), while amyloglucosidase with 600 U/g of biomass obtained 76.57 ± 6.42% (w/w). The combination of two enzymes simultaneously was more efficient than the sequential addition for low enzyme concentrations (α-amylase 50 U/g and amyloglucosidase 90 U/g) with a total reducing sugar of 22.78 ± 3.06 and 16.92 ± 2.06% (w/w), respectively. On the other hand, using the higher enzymes concentrations, no difference was observed between the two addition strategies, 58.9 ± 3.55 and 57.05 ± 2.33% (w/w) for the sequential and simultaneous, respectively. Both strategies didn’t present advantage, since the amyloglucosidase enzyme alone produced slightly higher results. Even thought, the obtained results showed successfully performed saccharification of microalgal biomass and clearly point to microalgae use for saccharification and subsequent bioethanol production.Part of this work has been supported by European governments (INTERREG VA-POCTEP- 2014-2020; 0055_ALGARED_PLUS_5_E) and the Portuguese Science Foundation (FCT) through the grant UID/MAR/00350/2013 to the CIMA of the University of Algarve.info:eu-repo/semantics/publishedVersio

Structure‐guided Capacitance Relationships in Oxidized Graphene Porous Materials Based Supercapacitors

Supercapacitors formed from porous carbon and graphene-oxide (GO) materials are usually dominated by either electric double-layer capacitance, pseudo-capacitance, or both. Due to these combined features, reduced GO materials have been shown to offer superior capacitance over typical nanoporous carbon materials; however, there is a significant variation in reported values, ranging between 25 and 350 F g−1. This undermines the structure (e.g., oxygen functionality and/or surface area)-performance relationships for optimization of cost and scalable factors. This work demonstrates important structure-controlled charge storage relationships. For this, a series of exfoliated graphene (EG) derivatives are produced via thermal-shock exfoliation of GO precursors and following controlled graphitization of EG (GEG) generates materials with varied amounts of porosity, redox-active oxygen groups and graphitic components. Experimental results show significantly varied capacitance values between 30 and 250 F g−1 at 1.0 A g−1 in GEG structures; this suggests that for a given specific surface area the redox-active and hydrophilic oxygen content can boost the capacitance to 250–300% higher compared to typical mesoporous carbon materials. GEGs with identical oxygen functionality show a surface area governed capacitance. This allows to establish direct structure-performance relationships between 1) redox-active oxygen functional concentration and capacitance and 2) surface area and capacitance