Biocatalytic Transfer of Pseudaminic Acid (Pse5Ac7Ac) Using Promiscuous Sialyltransferases in a Chemoenzymatic Approach to Pse5Ac7Ac-Containing Glycosides

Pseudaminic acid (Pse5Ac7Ac) is a nonmammalian sugar present on the cell surface of a number of bacteria including Pseudomonas aeruginosa, Campylobacter jejuni, and Acinetobacter baumannii. However, the role Pse5Ac7Ac plays in host–pathogen interactions remains underexplored, particularly compared to its ubiquitous sialic acid analogue Neu5Ac. This is primarily due to a lack of access to difficult to prepare Pse5Ac7Ac glycosides. Herein, we describe the in vitro biocatalytic transfer of an activated Pse5Ac7Ac donor onto glycosyl acceptors, enabling the enzymatic synthesis of Pse5Ac7Ac-containing glycosides. In a chemoenzymatic approach, chemical synthesis initially afforded access to a late-stage Pse5Ac7Ac biosynthetic intermediate, which was subsequently converted to the desired CMP-glycosyl donor in a one-pot two-enzyme process using biosynthetic enzymes. Finally, screening a library of 13 sialyltransferases (SiaT) with the unnatural substrate enabled the identification of a promiscuous inverting SiaT capable of turnover to afford β-Pse5Ac7Ac-terminated glycosides.</p

Short synthesis of the common trisaccharide core of kankanose and kankanoside isolated from Cistanche tubulosa

A short synthetic approach was developed for the synthesis of a common trisaccharide core found in kankanose, kankanoside F, H1, H2, and I isolated from the medicinally active plant Cistanche tubulosa. All glycosylations were carried out under nonmetallic reaction conditions. Yields were very good in all intermediate steps

Solution-Processed 2D PbS Nanoplates with Residual Cu₂S Exhibiting Low Resistivity and High Infrared Responsivity

We report the synthesis of colloidal 2D PbS nanoplates with residual Cu₂S domains via a partial cation-exchange process involving Pb²⁺ and presynthesized hexagonal Cu₂S nanoplates with an average thickness of ∼3 nm and edge lengths of ∼150 nm. Different from previously reported PbS nanosheets whose basal planes are ±{100}_PbS, our approach yields nanoplates whose basal planes are ±{111}_PbS, which was previously theoretically predicted to have better surface ligand passivation. Subsequently, we found that the PbS nanoplates showed improved colloidal stability and did not suffer from severe aggregation despite numerous solvent wash steps. We further incorporated a film of nanoplates into a planar photodetector device with lateral Au electrodes. The amount of residual Cu₂S in the PbS nanoplates, which can be tuned by adjusting the reaction time of the cation-exchange process, was found to play a crucial role in determining the in-plane conductivity of the film and therefore its photodetection efficiency. For PbS nanoplates with 7.8% residual Cu⁺, the responsivity and specific detectivity at 808 nm was ∼1739 A/W and ∼2.55 × 10¹¹ Jones, respectively. The high responsivity was attributed to the very low PbS nanoplate film resistivity of 8.04 ohm·cm, which is comparable to commercial doped semiconductors

Hybrid Antibiotic Overcomes Resistance in P. aeruginosa by Enhancing Outer Membrane Penetration and Reducing Efflux

Therapeutic interventions to treat multidrug-resistant (MDR) Pseudomonas aeruginosa infections are severely limited and often require the use of colistin as drug of last resort. The major challenges impeding the development of novel antipseudomonal agents are the lack of cell penetration and extensive efflux. We have discovered a tobramycin–moxifloxacin hybrid core structure which enhances outer membrane permeability and reduces efflux by dissipating the proton motive force of the cytoplasmic membrane in P. aeruginosa. The optimized hybrid protects Galleria mellonella larvae from the lethal effects of MDR P. aeruginosa. Attempts to select for resistance over a period of 25 days resulted in a 2-fold increase in the minimal inhibitory concentration (MIC) for the hybrid, while moxifloxacin or tobramycin resulted in a 16- and 512-fold increase in MIC. Although the hybrid possesses potent activity against MDR, P. aeruginosa isolates the activity that can be synergized when used in combination with other classes of antibiotics

Hybrid Antibiotic Overcomes Resistance in P. aeruginosa by Enhancing Outer Membrane Penetration and Reducing Efflux

Therapeutic interventions to treat multidrug-resistant (MDR) Pseudomonas aeruginosa infections are severely limited and often require the use of colistin as drug of last resort. The major challenges impeding the development of novel antipseudomonal agents are the lack of cell penetration and extensive efflux. We have discovered a tobramycin–moxifloxacin hybrid core structure which enhances outer membrane permeability and reduces efflux by dissipating the proton motive force of the cytoplasmic membrane in P. aeruginosa. The optimized hybrid protects Galleria mellonella larvae from the lethal effects of MDR P. aeruginosa. Attempts to select for resistance over a period of 25 days resulted in a 2-fold increase in the minimal inhibitory concentration (MIC) for the hybrid, while moxifloxacin or tobramycin resulted in a 16- and 512-fold increase in MIC. Although the hybrid possesses potent activity against MDR, P. aeruginosa isolates the activity that can be synergized when used in combination with other classes of antibiotics

Effect of TaN intermediate layer on the back contact reaction of sputter-deposited Cu poor Cu2ZnSnS4 and Mo

Ultrathin tantalum nitride (TaN) intermediate layers (IL) with thickness from 3 nm to 12 nm have been used to limit the undesirable interfacial reaction between molybdenum (Mo) and copper-zinc-tin-sulphide (CZTS). The morphology, chemical and structural properties of the samples were characterized by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, X-ray diffraction analysis, and scanning transmission electron microscopy (STEM). Time-of-flight secondary ion mass spectrometry (TOFSIMS), energy-dispersive X-ray spectroscopy (EDX), and electron energy loss spectroscopy (EELS) have been used for elemental analysis. Thin TaN IL shows chemical reactivity towards sulphur (S) vapor at 600 °C and the incorporation of S in TaN reduces the S concentration in Mo films at the sub-surface region and thus improves electrical conductivity of sulphurised Mo. The use of a non-stoichiometric quaternary compound CZTS target along with TaN IL enables to minimise thickness of MoS 2 layer and reduce void formation at the Mo/CZTS interface. Furthermore, incorporation of TaN IL improves scratch hardness of CZTS/Mo films to soda-lime glass substrate

Tin oxide for optoelectronic, photovoltaic and energy storage devices: a review

Tin dioxide (SnO2), the most stable oxide of tin, is a metal oxide semiconductor that finds its use in a number of applications due to its interesting energy band gap that is easily tunable by doping with foreign elements or by nanostructured design such as thin film, nanowire or nanoparticle formation, etc., and its excellent thermal, mechanical and chemical stability. In particular, its earth abundance and non-toxicity make it very attractive for use in a number of technologies for sustainable development such as energy harvesting and storage. This article attempts to review the state of the art of synthesis and properties of SnO2, focusing primarily on its application as a transparent conductive oxide (TCO) in various optoelectronic devices and second in energy harvesting and energy storage devices where it finds its use as an electron transport layer (ETL) and an electrode material, respectively. In doing so, we discuss how tin oxide meets the requirements for the above applications, the challenges associated with these applications, and how its performance can be further improved by adopting various strategies such as doping with foreign metals, functionalization with plasma, etc. The article begins with a review on the various experimental approaches to doping of SnO2 with foreign elements for its enhanced performance as a TCO as well as related computational studies. Herein, we also compare the TCO performance of doped tin oxide as a function of dopants such as fluorine (F), antimony (Sb), tantalum (Ta), tungsten (W), molybdenum (Mo), phosphorus (P), and gallium (Ga). We also discuss the properties of multilayer SnO2/metal/SnO2 structures with respect to TCO performance. Next, we review the status of tin oxide as a TCO and an ETL in devices such as organic light emitting diodes (OLEDs), organic photovoltaics (OPV), and perovskite solar cells (including plasma treatment approaches) followed by its use in building integrated photovoltaic (BIPV) applications. Next, we review the impact of SnO2, mainly as an electrode material on energy storage devices starting from the most popular lithium (Li)-ion batteries to Li–sulfur batteries and finally to the rapidly emerging technology of supercapacitors. Finally, we also compare the performance of doped SnO2 with gallium (Ga) doped zinc oxide (ZnO), the main sustainable alternative to SnO2 as a TCO and summarize the impact of SnO2 on circular economies and discuss the main conclusions and future perspectives. It is expected that the review will serve as an authoritative reference for researchers and policy makers interested in finding out how SnO2 can contribute to the circular economy of some of the most desired sustainable and clean energy technologies including the detailed experimental methods of synthesis and strategies for performance enhancement