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Lithium-ion intercalation by coupled ion-electron transfer
No full textLithium-ion batteries are powering a revolution in electrification, but the underlying intercalation mechanism at the electrified interface remains poorly understood. Here, we provide experimental and theoretical evidence that lithium intercalation occurs by coupled ion-electron transfer (CIET), in which classical ion transfer from the electrolyte is coupled with quantum-mechanical electron transfer from the electrode to form an ion-electron pair in the reduced state. Current-voltage responses and reaction-limited capacities, corresponding to small and large overpotentials, respectively, were measured for common electrode materials and linked by the theory. The experiments showed universal dependence of the (de-)intercalation rate on Li-ion filling fraction, as well as temperature and electrolyte effects consistent with the theory. These results could be used to guide the design of high-rate battery interfaces that maximize the CIET reaction-limited current
Possibilities and limits of DNA-enabled programmable 2D self-assembly
No full textProgrammable self-assembly provides a promising avenue to improve upon traditional synthesis and create multi-component materials with emergent properties and arbitrary nanoscale complexity. However, its most successful realizations utilizing DNA often use complicated arduous procedures that result in low yields. Here, we employ coarse-grained molecular dynamics to uncover the ranges of temperatures and misbinding strengths needed for successful one-pot self-assembly of generic, two-dimensional (2D), and distinguishable blocks. Analysis of the energies associated with a single-stranded DNA interacting with all other sequences within a mixture revealed that the success of DNA-based assembly is primarily determined by the strongest misbinding a given sequence can encounter with a sequence highly similar to its reverse complement. This enabled us to design optimized sequence ensembles with acceptably weak and consequently rare misbinding. An estimate is provided for the maximum size of, and complexity of sequences needed to synthesize self-assembled structures with high accuracy and yield, with potential relevance for DNA-functionalized low-dimensional materials for electronics and energy storage
Characterization of a monoclonal antibody by native and denaturing top-down mass spectrometry
No full textEstablished in recent years as an important approach to unraveling the heterogeneity of intact monoclonal antibodies, native mass spectrometry has been rarely utilized for sequencing these complex biomolecules via tandem mass spectrometry. Typically, top-down mass spectrometry has been performed starting from highly charged precursor ions obtained via electrospray ionization under denaturing conditions (i.e., in the presence of organic solvents and acidic pH). Here we systematically benchmark four distinct ion dissociation methods – namely higher-energy collisional dissociation, electron transfer dissociation, electron transfer dissociation/higher-energy collisional dissociation, and 213 nm ultraviolet photodissociation – in their capability to characterize a therapeutic monoclonal antibody, trastuzumab, starting from denatured and native-like precursor ions. Interestingly, native top-down mass spectrometry results in higher sequence coverage than the experiments carried out under denaturing conditions, with the exception of ultraviolet photodissociation. Globally, electron transfer dissociation followed by collision-based activation of product ions generates the largest number of backbone cleavages in disulfide protected regions, including the complementarity determining regions, regardless of electrospray ionization conditions. Overall, these findings suggest that native mass spectrometry can certainly be used for the gas-phase sequencing of whole monoclonal antibodies, although the dissociation of denatured precursor ions still returns a few backbone cleavages not identified in native experiments. Finally, a comparison of the fragmentation maps obtained under denaturing and native conditions strongly points towards disulfide bonds as the primary reason behind the largely overlapping dissociation patterns
Photoexcitation and One-Electron Reduction Processes of a CO2 Photoreduction Dyad Catalyst Having a Zinc(II) Porphyrin Photosensitizer
No full textWe have explored the photophysical properties and one electron reduction process in the dyad photocatalyst for CO2 photoreduction, ZnP-phen=Re, in which the catalyst of fac-[Re(1,10-phenanthoroline)(CO)3Br] (phen=Re) is directly connected with the photosensitizer of zinc (II) porphyrin (ZnP), using time-resolved infrared spectroscopy, transient absorption spectroscopy, and quantum chemical calculations. We revealed the photophysical properties that (1) the intersystem crossing occurs with a time constant of ~20 ps, which is more than 50 times faster than that of zinc (II) porphyrin, and (2) the charge density in the excited singlet and triplet states is mainly localized on ZnP, which means the excited state is assignable to the π -π* transition in ZnP. The one electron reduction using the reductant, 1,3-dimethyl-2-,3-dihydro-1H-benzo[d]imidazole (BIH), occurs via the triplet excited state with time constant of ~170 ns and directly from the ground state by the deprotonated BIH with the time constant of ~3 μs. The charge in the one electron reduction species spans ZnP and the phenanthroline ligand and the dihedral angle between ZnP and the phenanthroline ligand is rotated by ~24° with respect to that in the ground state, which presumably offers an advantage for proceeding to the next CO2 reduction reaction step. These findings on the initial processes of CO2 photoreduction would help us to design novel dyad photocatalysts using porphyrin photosensitizers
Establishment and characterization of noro-VLP measurement by digital ELISA
No full textHighly sensitive viral analytical techniques are essential tools for preventing the spread of infections. In this study, we established a digital enzyme-linked immunosorbent assay (ELISA) system to quantify norovirus proteins with high sensitivity. We used norovirus-like particles (noro-VLPs) as a surrogate for norovirus and constructed two digital ELISA systems using two different antibody pairs. The quantitative performance of the noro-VLP measurement using each digital ELISA system was evaluated. Both assay systems exhibited high sensitivity, good linearity, and high stability. The first system exhibited a limit of detection (LOD) of 87 pg/mL, correlation coefficient (R2) of 0.9984, inter-assay variation of 5.5 %, and intra-assay variation of 5.2 %. The second system exhibited an LOD of 19 pg/mL, R2 of 0.9984, inter-assay variation of 4.5 %, and intra-assay variation of 2.5 %. Comparison of the two systems using the same calibrant for unpurified and fractionated noro-VLPs revealed that the quantitative values for unpurified noro-VLPs were the same, whereas those for fractionated noro-VLPs were dramatically different. Our findings indicate that the reactivity to various components in the noro-VLP solution was altered depending on the different antibodies. Furthermore, our study highlights the importance of using appropriate calibrants, which contain the same ratio of components as the noro-VLP analyte, to afford accurate measurements
Effect of Filler Surface Chemistry on the Multifunctional Properties of GNP Epoxy Nanocomposites
No full textPlasma reactors can be used to surface functionalise industrial scale (tonnes/annum) quantities of graphene nanoplatelets (GNPs). When used as fillers in polymer nanocomposites, surface functionalisation of GNPs can modify the chemical interactions at the filler-matrix interphase. In this work baseline (PG-10), plasma fluorinated (PG-CF), and aminated (PG-NH) GNPs were used to manufacture GNP epoxy nanocomposites, and their multifunctional properties tested. We find that the high aspect ratio and homogeneous dispersion of PG-NH enables a ~75% increase in filler modulus and reduces the thermal conductivity. While the high density of low lateral size particulates in PG-CF nanocomposites, reduces the filler modulus by ~50%, and increases the thermal conductivity. We link filler surface chemistry, to the dispersion and morphology of flakes in the matrix, and the resultant nanocomposite multifunctional properties. Demonstrating that surface functionalisation can be carried out in a scalable manner to improve filler-matrix property transfer in GNP epoxy nanocomposites
Nanospike Nickel-Iron Oxalate as an Efficient Electrocatalyst for the Oxygen Evolution Reaction
No full textObtaining hydrogen as a renewable fuel through water splitting is severely hindered by the energy-intensive oxygen evolution reaction (OER). Transition metal oxides based on low-cost and earth-abundant elements have been shown to provide high OER rivaling that of commercial IrO2, with nickel iron oxide/oxyhydroxide systems exhibiting some of the lowest reported overpotentials. Here, we report a nickel-iron oxalate material with a nanospike morphology synthesized via a simple and novel hydrothermal method, in which oxalate is generated in situ during material preparation under mild conditions. The as-synthesized nanostructured material displays high catalytic activity for OER, requiring a low overpotential of only 284 mV at a current density of 10 mA·cm−2, lower than that of its amorphous counterpart and commercial IrO2 (326 and 308 mV, respectively). This material also exhibits excellent long-term stability with retention of the nanospike morphology after several hours under OER conditions
Enabling Cellular Resolution Molecular Pathology for Surgical Interventions Using Laser Desorption – Rapid Evaporative Ionization Mass spectrometry
No full textLaser desorption ionization (LDI) is generally considered to be an inferior ionization modality to matrix assisted LDI (MALDI), providing information solely on lipids with low sensitivity. The current study demonstrates that the combination of ambient LDI with in-source surface-induced declustering provides sensitivity and chemical coverage comparable to MALDI. The setup was characterised for infrared laser desorption using two different laser systems and was successfully used for ambient mass spectrometric imaging. 5 µm spatial resolution was achieved enabling single-cell resolution imaging, while metabolites and lipids ranging from amino acids through carbohydrates and nuclear bases to complex glycolipids were successfully detected. The technique was also tested as a platform for MS-guided surgery, raising the possibility of using a single technique for generating histological and in-vivo data. The results suggest that the method can be an important step forward in histological classification for surgery and pathology environments, potentially offering a versatile platform for generating both histological and in vivo data
A Skeletally Diverse Library of Bioactive Natural Product-Like Compounds Enabled by Late-Stage P450-Catalyzed Oxyfunctionalization
No full textThe discovery of small-molecule agents for chemical biology and therapeutic applications depends upon the ability to access and explore new biologically relevant regions of chemical space, a goal often pursued through diversity-oriented synthesis (DOS). In this report, we describe the design and implementation of P450-mediated chemoenzymatic diversity-oriented synthesis (CeDOS), a strategy that leverages chemo- and regiodivergent P450-catalyzed oxyfunctionalizations as key steps for enabling the synthesis of complex molecules that resemble natural products, a major source of bioactive molecules and drugs. Using this strategy, a library of over 50 novel and structurally diverse natural product-like compounds was generated through skeletal rearrangement and diversification of a plant-derived terpene via divergent chemoenzymatic routes enabled by selective C–H hydroxylation and epoxidation reactions catalyzed by engineered P450s. This CeDOS library encompass many unique and unprecedented organic scaffolds, many of which were determined to exhibit notable cytotoxicity against human cancer cells as well as diversified anticancer activity profiles. This work demonstrates the power of the present chemoenzymatic diversity-oriented synthesis strategy for directing the construction and discovery of novel bioactive molecules and it offers a blueprint for the broader application of this approach toward the creation and exploration of natural product-like chemical libraries
Theoretical Investigation of Interactions between HIV-1 Tat and p53 proteins
No full textHIV-1 Tat (transactivator of transcription) protein is the main arsenal of HIV, playing numerous roles during viral infection. This protein is inherently disordered, lacking any secondary structures. This plasticity allows HIV-1 Tat to engage in interaction with multiple proteins and biological molecules, resulting in either collapse of the immune system or severe damage to tissues. Proteomic studies previously revealed p53, commonly cited as the guardian angel of the genome to interact with the Tat protein through its tetramerization domain. As p53 is crucial in terms of whether the cell dies or lives, its interaction with the Tat protein is of broad interest in the pathogenesis of HIV infection. For this reason, we investigated the complexation between the Tat protein and the tetramerization domain of p53 using molecular docking and molecular dynamics simulations. We believe that the results reported in this manuscript are of great significance for developing novel therapeutic agents targeting the p53/Tat interaction