Surface Transport Properties of Pb-Intercalated Graphene

Intercalation experiments on epitaxial graphene are attracting a lot of attention at present as a tool to further boost the electronic properties of 2D graphene. In this work, we studied the intercalation of Pb using buffer layers on 6H-SiC(0001) by means of electron diffraction, scanning tunneling microscopy, photoelectron spectroscopy and in situ surface transport. Large-area intercalation of a few Pb monolayers succeeded via surface defects. The intercalated Pb forms a characteristic striped phase and leads to formation of almost charge neutral graphene in proximity to a Pb layer. The Pb intercalated layer consists of 2 ML and shows a strong structural corrugation. The epitaxial heterostructure provides an extremely high conductivity of σ=100 mS/□. However, at low temperatures (70 K), we found a metal-insulator transition that we assign to the formation of minigaps in epitaxial graphene, possibly induced by a static distortion of graphene following the corrugation of the interface layer.

Mycobacterium abscessus Genetic Determinants Associated with the Intrinsic Resistance to Antibiotics

Mycobacterium abscessus subsp. abscessus (MAB) is a fast-growing nontuberculous mycobacterium causing pulmonary infections in immunocompromised and immunocompetent individuals. The treatment of MAB infections in clinics is extremely challenging, as this organism is naturally resistant to most available antibiotics. There is limited knowledge on the mechanisms of MAB intrinsic resistance and on the genes that are involved in the tolerance to antimicrobials. To identify the MAB genetic factors, including the components of the cell surface transport systems related to the efflux pumps, major known elements contributing to antibiotic resistance, we screened the MAB transposon library of 2000 gene knockout mutants. The library was exposed at either minimal inhibitory (MIC) or bactericidal concentrations (BC) of amikacin, clarithromycin, or cefoxitin, and MAB susceptibility was determined through the optical density. The 98 susceptible and 36 resistant mutants that exhibited sensitivity below the MIC and resistance to BC, respectively, to all three drugs were sequenced, and 16 mutants were found to belong to surface transport systems, such as the efflux pumps, porins, and carrier membrane enzymes associated with different types of molecule transport. To establish the relevance of the identified transport systems to antibiotic tolerance, the gene expression levels of the export related genes were evaluated in nine MAB clinical isolates in the presence or absence of antibiotics. The selected mutants were also evaluated for their ability to form biofilms and for their intracellular survival in human macrophages. In this study, we identified numerous MAB genes that play an important role in the intrinsic mechanisms to antimicrobials and further demonstrated that, by targeting components of the drug efflux system, we can significantly increase the efficacy of the current antibiotics.

MmpA, a Conserved Membrane Protein Required for Efficient Surface Transport of Trehalose Lipids in Corynebacterineae

Cell walls of bacteria of the genera Mycobacterium and Corynebacterium contain high levels of (coryno)mycolic acids. These very long chain fatty acids are synthesized on the cytoplasmic leaflet of the inner membrane (IM) prior to conjugation to the disaccharide, trehalose, and transport to the periplasm. Recent studies on Corynebacterium glutamicum have shown that acetylation of trehalose monohydroxycorynomycolate (hTMCM) promotes its transport across the inner membrane. Acetylation is mediated by the membrane acetyltransferase, TmaT, and is dependent on the presence of a putative methyltransferase, MtrP. Here, we identify a third protein that is required for the acetylation and membrane transport of hTMCM. Deletion of the C. glutamicum gene NCgl2761 (Rv0226c in Mycobacterium tuberculosis) abolished synthesis of acetylated hTMCM (AcTMCM), resulting in an accumulation of hTMCM in the inner membrane and reduced synthesis of trehalose dihydroxycorynomycolate (h2TDCM), a major outer membrane glycolipid. Complementation with the NCgl2761 gene, designated here as mmpA, restored the hTMCM:h2TDCM ratio. Comprehensive lipidomic analysis of the ΔtmaT, ΔmtrP and ΔmmpA mutants revealed strikingly similar global changes in overall membrane lipid composition. Our findings suggest that the acetylation and membrane transport of hTMCM is regulated by multiple proteins: MmpA, MtrP and TmaT, and that defects in this process lead to global, potentially compensatory changes in the composition of inner and outer membranes.

The kinesin KIF4 mediates HBV/HDV entry through regulation of surface NTCP localization and can be targeted by RXR agonists in vitro.

Intracellular transport via microtubule-based dynein and kinesin family motors plays a key role in viral reproduction and transmission. We show here that Kinesin Family Member 4 (KIF4) plays an important role in HBV/HDV infection. We intended to explore host factors impacting the HBV life cycle that can be therapeutically addressed using siRNA library transfection and HBV/NLuc (HBV/NL) reporter virus infection in HepG2-hNTCP C4 cells. KIF4 silencing resulted in a 3-fold reduction in luciferase activity following HBV/NL infection and suppressed both wild-type HBV and HDV infection. Transient KIF4 depletion reduced surface and raised intracellular NTCP (HBV/HDV entry receptor) levels, according to both cellular fractionation and immunofluorescence analysis (IF). Overexpression of wild-type KIF4 but not ATPase-null KIF4 regains the surface localization of NTCP in these cells. Furthermore, IF revealed KIF4 and NTCP colocalization across microtubule filaments, and a co-immunoprecipitation study revealed that KIF4 physically binds to NTCP. KIF4 expression is regulated by FOXM1. Interestingly, we discovered that RXR agonists (Bexarotene, and Alitretinoin) down-regulated KIF4 expression via FOXM1 mediated suppression, resulting in a substantial decrease in HBV-Pre-S1 protein attachment to HepG2-hNTCP cell surface and subsequent HBV infection in HepG2-hNTCP and primary human hepatocytes (PXB) (Bexarotene, IC 50 1.89 ± 0.98 μM). Overall, our findings show that human KIF4 is a critical regulator of NTCP surface transport and localization, which is required for NTCP to function as a receptor for HBV/HDV entry. Furthermore, small molecules that suppress or alleviate KIF4 expression would be potential antiviral candidates that target HBV and HDV entry phase.

Laboratory studies of the role of bandwidth in surface transport and energy dissipation of deep-water breaking waves

This paper presents laboratory measurements of surface transport due to non-breaking and breaking deep-water focusing surface wave packets and examines the dependence of the transport on the wave packet bandwidth, $\varDelta$ . This extends the work of Deike et al. (J. Fluid Mech., vol. 829, 2017, pp. 364–391) and Lenain et al. (J. Fluid Mech., vol. 876, 2019, p. R1), where similar numerical and laboratory experiments were conducted, but the bandwidth was held constant. In this paper, it is shown that the transport is strongly affected by the bandwidth. A model for the horizontal length scale of the breaking region is proposed that incorporates the bandwidth, central frequency, the linear prediction of the slope at focusing and the breaking threshold slope of the wave packet. This is then evaluated with data from archived and new laboratory experiments, and agreement is found. Furthermore, the horizontal length scale of the breaking region implies modifications to the model of the energy dissipation rate from Drazen et al. (J. Fluid Mech., vol. 611, 2008, pp. 307–332). This modification accounts for differing trends in the dissipation rate caused by the bandwidth in the available laboratory data.

Impact of Regional Air connectivity on Regional Economic Growth in India

In this study, we have used the panel data of 15 federal states to evaluate the empirical linkages between regional economic growth, air transport traffic, and surface transport indicators. There is a dearth of academic articles focusing on inter-dependence between these factors in the context of India. Pedroni panel cointegration, FMOLS, panel VECM causality techniques, and variance decomposition analysis have been used to evaluate dynamics between the three variables. The evaluation of linkages between the regional air connectivity and the regional economic growth holds practical implications since it forms the basis of various policy and regulatory measures instituted in the Indian air transport sector. The bidirectional relationship between air transport and surface transport indicators calls for making multi-modal studies by experts as guiding force behind planning processes instead of relying purely on bureaucratic consultation.