8 research outputs found
3D-imaging of Printed Nanostructured Networks using High-resolution FIB-SEM Nanotomography
Networks of solution-processed nanomaterials are important for multiple
applications in electronics, sensing and energy storage/generation. While it is
known that network morphology plays a dominant role in determining the physical
properties of printed networks, it remains difficult to quantify network
structure. Here, we utilise FIB-SEM nanotomography to characterise the
morphology of nanostructured networks. Nanometer-resolution 3D-images were
obtained from printed networks of graphene nanosheets of various sizes, as well
as networks of WS2 nanosheets, silver nanosheets and silver nanowires.
Important morphological characteristics, including network porosity,
tortuosity, pore dimensions and nanosheet orientation were extracted and linked
to network resistivity. By extending this technique to interrogate the
structure and interfaces within vertical printed heterostacks, we demonstrate
the potential of this technique for device characterisation and optimisation.Comment: 6 figure
Cyclic production of biocompatible few-layer graphene ink with in-line shear-mixing for inkjet-printed electrodes and Li-ion energy storage
The scalable production of two-dimensional (2D) materials is needed to accelerate their adoption to industry. In this work, we present a low-cost in-line and enclosed process of exfoliation based on high-shear mixing to create aqueous dispersions of few-layer graphene, on a large scale with a Yw ~ 100% yield by weight and throughput of ϕ ~ 8.3 g h−1. The in-line process minimises basal plane defects compared to traditional beaker-based shear mixing which we attribute to a reduced Reynolds number, Re ~ 105. We demonstrate highly conductive graphene material with conductivities as high as σ ∼ 1.5 × 104 S m−1 leading to sheet-resistances as low as Rs ∼ 2.6 Ω □−1 (t ∼ 25 μm). The process is ideal for formulating non-toxic, biocompatible and highly concentrated (c ∼ 100 mg ml−1) inks. We utilise the graphene inks for inkjet printable conductive interconnects and lithium-ion battery anode composites that demonstrate a low-rate lithium storage capability of 370 mAh g−1, close to the theoretical capacity of graphite. Finally, we demonstrate the biocompatibility of the graphene inks with human colon cells and human umbilical vein endothelial cells at high c ∼ 1 mg ml−1 facilitating a route for the use of the graphene inks in applications that require biocompatibility at high c such as electronic textiles.publishedVersio
Structural basis of the membrane intramolecular transacylase reaction responsible for lyso-form lipoprotein synthesis
Abstract: Lipoproteins serve diverse functions in the bacterial cell and some are essential for survival. Some lipoproteins are adjuvants eliciting responses from the innate immune system of the host. The growing list of membrane enzymes responsible for lipoprotein synthesis includes the recently discovered lipoprotein intramolecular transacylase, Lit. Lit creates a lipoprotein that is less immunogenic, possibly enabling the bacteria to gain a foothold in the host by stealth. Here, we report the crystal structure of the Lit enzyme from Bacillus cereus and describe its mechanism of action. Lit consists of four transmembrane helices with an extracellular cap. Conserved residues map to the cap-membrane interface. They include two catalytic histidines that function to effect unimolecular transacylation. The reaction involves acyl transfer from the sn-2 position of the glyceryl moiety to the amino group on the N-terminal cysteine of the substrate via an 8-membered ring intermediate. Transacylation takes place in a confined aromatic residue-rich environment that likely evolved to bring distant moieties on the substrate into proximity and proper orientation for catalysis
Quantifying the contribution of material and junction resistances in nano-networks
Networks of nanowires and nanosheets are important for many applications in
printed electronics. However, the network conductivity and mobility are usually
limited by the inter-particle junction resistance, a property that is
challenging to minimise because it is difficult to measure. Here, we develop a
simple model for conduction in networks of 1D or 2D nanomaterials, which allows
us to extract junction and nanoparticle resistances from
particle-size-dependent D.C. resistivity data of conducting and semiconducting
materials. We find junction resistances in porous networks to scale with
nanoparticle resistivity and vary from 5 Ohm for silver nanosheets to 25 GOhm
for WS2 nanosheets. Moreover, our model allows junction and nanoparticle
resistances to be extracted from A.C. impedance spectra of semiconducting
networks. Impedance data links the high mobility (~7 cm2/Vs) of aligned
networks of electrochemically exfoliated MoS2 nanosheets to low junction
resistances of ~670 kOhm. Temperature-dependent impedance measurements allow us
to quantitatively differentiate intra-nanosheet phonon-limited band-like
transport from inter-nanosheet hopping for the first time.Comment: 5 figure
The SARS-CoV-2 envelope (E) protein forms a calcium-and voltage-activated calcium channel
Computational Design of Cyclic Peptide Inhibitors of a Bacterial Membrane Lipoprotein Peptidase
There remains a critical need for new antibiotics against multi-drug-resistant Gram-negative bacteria, a major global threat that continues to impact mortality rates. Lipoprotein signal peptidase II is an essential enzyme in the lipoprotein biosynthetic pathway of Gram-negative bacteria, making it an attractive target for antibacterial drug discovery. Although natural inhibitors of LspA have been identified, such as the cyclic depsipeptide globomycin, poor stability and production difficulties limit their use in a clinical setting. We harness computational design to generate stable de novo cyclic peptide analogues of globomycin. Only 12 peptides needed to be synthesized and tested to yield potent inhibitors, avoiding costly preparation of large libraries and screening campaigns. The most potent analogues showed comparable or better antimicrobial activity than globomycin in microdilution assays against ESKAPE-E pathogens. This work highlights computational design as a general strategy to combat antibiotic resistance. </p
Computational design of cyclic peptide inhibitors of a bacterial membrane lipoprotein peptidase
There remains a critical need for new antibiotics against multi-drug-resistant Gram-negative bacteria, a major global threat that continues to impact mortality rates. Lipoprotein signal peptidase II is an essential enzyme in the lipoprotein biosynthetic pathway of Gram-negative bacteria, making it an attractive target for antibacterial drug discovery. Although natural inhibitors of LspA have been identified, such as the cyclic depsipeptide globomycin, poor stability and production difficulties limit their use in a clinical setting. We harness computational design to generate stable de novo cyclic peptide analogues of globomycin. Only 12 peptides needed to be synthesized and tested to yield potent inhibitors, avoiding costly preparation of large libraries and screening campaigns. The most potent analogues showed comparable or better antimicrobial activity than globomycin in microdilution assays against ESKAPE-E pathogens. This work highlights computational design as a general strategy to combat antibiotic resistance.</p
Computational Design of Cyclic Peptide Inhibitors of a Bacterial Membrane Lipoprotein Peptidase
There remains a critical need for new antibiotics against multi-drug-resistant Gram-negative bacteria, a major global threat that continues to impact mortality rates. Lipoprotein signal peptidase II is an essential enzyme in the lipoprotein biosynthetic pathway of Gram-negative bacteria, making it an attractive target for antibacterial drug discovery. Although natural inhibitors of LspA have been identified, such as the cyclic depsipeptide globomycin, poor stability and production difficulties limit their use in a clinical setting. We harness computational design to generate stable de novo cyclic peptide analogues of globomycin. Only 12 peptides needed to be synthesized and tested to yield potent inhibitors, avoiding costly preparation of large libraries and screening campaigns. The most potent analogues showed comparable or better antimicrobial activity than globomycin in microdilution assays against ESKAPE-E pathogens. This work highlights computational design as a general strategy to combat antibiotic resistance. </p