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Sequence-Controlled Divergent Supramolecular Assembly of Polyproline Helices into Metallo-Peptide Nanoparticles
No full textThe field of peptide based supramolecular biomaterials is fast evolving. These types of constructs have been shown to find applications in the fields of bioimaging, drug delivery and scaffolds for chemical reactions. However, the community typically focuses on the use of two specific class of structured peptides: alpha-helices and beta-sheets, clearly neglecting a unique peptide secondary structure:
the polyproline helix. Herein, we report the first design, synthesis and characterization of polyproline based metallo-peptide nanoparticles. We demonstrate that rationally engineered polyproline helices can assemble in a divergent manner, into two types of nanoparticles. We also demonstrate that the primary sequence of the functionalised polyproline peptide, is crucial to ensure a controlled assembly. This work clearly demonstrates that polyproline helices can be a powerful tool to achieve
supramolecular assemblies of complex and responsive bioinspired nanomaterials
Isomerization Cationic Ring-Opening Polymerization of CO2-Based Disubstituted-δ-Valerolactone
No full textThe challenging ring-opening homo-polymerization of α-ethylidene-δ-vinyl-δ-valerolactone (EVL), de-rived from CO2 and 1,3-butadiene, has aroused ex-tensive attention in consideration of economic effi-ciency and functionalization potential. Here, we achieve the first cationic ring-opening polymeriza-tion (CROP) of EVL, yielding well-defined polyester PEVL with number average molecular weight up to 12.8 kg/mol and low dispersity of 1.2. The obtained PEVL contains two kinds of structural units derived from EVL and three kinds of alkenyl groups, indicat-ing an isomerization during propagation. The isom-erization is necessary to the propagation, evidenced by density functional theory (DFT) calculation and unavailable CROP of the semi-hydrogenated EVL de-rivative without δ-vinyl group (α-ethylidene-δ-ethyl-δ-valerolactone). The fast intramolecular transfer reaction and slow initiation result in the cyclic to-pology fidelity of PEVL, providing the first example of quantitative formation of cyclic polyester in CROP. PEVL is degradable and recyclable, possessing a low glass transition temperature (Tg) of -33.6 ℃, while the product after modification with 1-octadecanethiol exhibits a melting point (Tm) of 42.2 ℃
Development and translation of a method of clinical utility for LC-MS/MS analysis to detect SARS-CoV-2 antigens from ONP swabs and saliva
No full textDuring the COVID-19 pandemic, development of diagnostic tests was vital to chart the course and to reduce the impact of the infection. Continued testing and surveillance of vaccine escape will continue for years to come which presents an opportunity to integrate such testing into clinical biochemistry laboratories that form part of integrated healthcare testing. Here we describe a protocol for a targeted mass spectrometry based proteomic assay (COVIDCAP) developed to detect SARS-CoV-2 peptides from oro-nasopharyngeal swabs (ONP) and saliva. This uses novel SISCAPA antibodies bound to magnetic beads and subsequent analysis of captured and purified SARS-CoV-2 nucleocapsid (NCAP) peptides. The method involves immediate deactivation of the sample using an ethanolic solution. This simultaneously inactivates the virus and denatures viral proteins at sampling in contrast to the approach for RT-PCR testing, with benefits for the assay as well as for downstream processing. A plate-based preparation of the samples involving acetone precipitation followed by a short tryptic digestion and subsequent immunocapture allows LC-MS detection and quantification of peptides from the NCAP protein, in a 3-minute inject-to-inject assay with an LOD of 20 attomoles from starting sample. For 576 ONP swab samples taken as exemplars here, the sensitivity and specificity of this analysis is shown to be 97.0% and 96.6% respectively
Methylammonium Lead Iodide across Physical Space -- Phase Boundaries and Structural Collapse
No full textHybrid perovskites exhibit complex structures and phase behavior under different thermodynamic conditions and chemical environments, the understanding of which continues to be of pivotal importance for tailoring their properties towards improved operational stability. To this end, we present for the first time a comprehensive neutron and synchrotron diffraction investigation over the pressure--temperature phase diagram of the paradigmatic hybrid organic-inorganic perovskite methylammonium lead iodide (MAPI). This ambitious experimental campaign down to cryogenic temperatures and tens of kbar was supported by extensive ab initio molecular dynamics simulations validated by the experimental data, to track the structural evolution of MAPI under external physical stimuli at the atomic and molecular levels. These combined efforts enable us to identify the mechanisms underpinning structural phase transitions, including those exhibiting negative thermal expansion across the boundary between the cation-ordered low-temperature phase and the dynamically disordered high-pressure cubic phase. Our results bring to the fore how pronounced octahedral distortions at high pressures ultimately drive the structural collapse and amorphization of this material
Investigating the origin of Automatic Rhodopsin Modeling outliers using the microbial Gloeobacter rhodopsin as testbed
No full textThe Automatic Rhodopsin Modeling (ARM) approach is a computational workflow devised for the automatic build up of hybrid quantum mechanics/molecular mechanics (QM/MM) models of wild-type rhodopsins and mutants, with the purpose of establish- ing trends in their photophysical and photochemical properties. Despite the success of ARM for accurately describing the visible light absorption maxima of many rhodopsins, for few cases, called outliers, it might lead to large deviations with respect to exper- iments. Applying ARM to Gloeobacter Rhodopsin (GR), a microbial rhodopsin with important applications in optogenetics, we analyze the origin of such outliers in the absorption energies obtained for GR wild-type and mutants at neutral pH, with a total root mean square deviation (RMSD) of 0.42 eV with respect to the experimen- tal GR excitation energies. Having discussed the importance and the uncertainty of one particular amino-acid pKa , namely histidine at position 87, we propose and test several modifications to the standard ARM protocol: (i) improved pKa predictions along with the consideration of several protonation microstates, (ii) attenuation of the opsin electrostatic potential at short-range, (iii) substitution of the state-average com- plete active space (CAS) electronic structure method by its state-specific approach, and (iv) complete replacement of CAS with mixed-reference spin-flip time-dependent density functional theory (MRSF-TDDFT). The best RMSD result we obtain is 0.2 eV combining the protonation of H87 and using MRSF/CAMH-B3LYP
Photocyclization of Fluorinated Acetophenones Unlocks an Efficient Way to Solar Energy Storage
No full textThe development of light-driven isomerization offers a promising avenue for energy storage applications. However, a persistent challenge lies in controlling the stability of the photoisomeric state and in catalyzing the thermal reversal effec-tively. In this work, we introduce the molecular pair ortho-methylacetophenone ⇄ benzocyclobutenol as a promising platform for long-term energy storage. To obtain an overall good performance, a trifluoromethyl group is strategically introduced. This group prevents unproductive reaction pathways during the photochemical cyclization (yield >99%), ensures stable photoisomers, and facilitates back-isomerization by critically lowering the pKa of the benzocyclobutenol scaffold. Thus, efficient reversal using simple organic bases is achieved, capitalizing on substantial rate differences for normal vs. anionic electrocyclic ring-openings. Ultimately, this discovery enables controlled heat release under ambient conditions
Visible Light-Controlled Intracellular Synthesis of Supramolecular Peptide Nanostructures
No full textThe complex dynamics and transience of supramolecular pathways in living cellular environments impede the correlation between diverse hierarchical species and their biological functions. The necessary breakthrough requires the precise control of supramolecular events at discrete time points via synthetic chemistry and their real-time visualization in native cells. Herein, we designed two peptide sequences that undergo a cascade of visible light-induced molecular and supramolecular transformations to form various assembly species in cells. In contrast to endogenous stimulus-responsive self-assembling systems, the irradiation with light enable full control over the reaction cascade where the monomer generation and concentration in turn regulates the assembly kinetics. Phasor-fluorescence lifetime imaging (phasor-FLIM) traced the formation of various assembly states in cells and revealed subsequent out-of-equilibrium dynamics associated with monomer activation and consumption. These temporally resolved assemblies show that the emergence of cytotoxicity is correlated to the accumulation of oligomers beyond the cellular efflux threshold
Structural and electronic properties of polyethylene terephthalate (PET) from polarizable molecular dynamics simulations
No full textThe environmental and economic challenges posed by the widespread use and disposal of plastics, particularly polyethylene terephthalate (PET), require innovative solutions to mitigate their impact. Such mitigation begins with understanding physical properties of the polymer that could enable new recycling technologies. Although molecular simulations have provided valuable insights into PET interactions with various PET hydrolases, current additive force fields neglect the electronic polarization effects inherent to PET interactions. Here, we present parameters for PET polymer and its derivatives that are compatible with the Drude polarizable force field. Our parameter fitting protocol accurately reproduces electrostatic properties from quantum mechanical calculations. We then studied electronic properties of PET amorphous slabs and PET crystal films, revealing a crucial electronic polarization response of PET residues at the interface with water or vacuum, yielding insights into the modulation of electrostatic properties by solvent molecules. Finally, we showcase the interaction between a carbohydrate-binding protein and the PET crystal film, revealing the role of electronic polarization in enhancing binding affinity. This study represents the first extension of the Drude polarizable force field to a synthetic polymer, offering a robust tool for exploring PET material properties and advancing the design of efficient (bio)technologies for addressing plastic pollution
Stable 25 % Efficiency Inorganic Perovskite/Organic Tandem Solar Cells Enabled by Methoxy-free D-A-D\u27-A-D Interconnecting Layer
No full textDeveloping dopant-free hole-transporting materials (HTMs) with high hole mobilities is essential to achieve efficient and stable inorganic perovskite solar cells (PVSCs). Herein, two linear organic small molecules IDTT-EtCz and IDTT-PhCz with D–A–D’–A–D configurations are designed and synthesized via two high yield steps, and they are successfully employed as HTMs with effective defect passivation in all-inorganic PVSCs. Notably, the IDTT-PhCz exhibits a deeper highest occupied molecular orbital energy level comparing with that of IDTT-EtCz, along with the enhancement of antioxidant activity towards iodine. Interestingly, IDTT-PhCz with aromatized terminal groups shows significantly increased short contacts and higher hole mobilities than IDTT-EtCz. Furthermore, the IDTT-PhCz has been proven to possess effective surface passivation capability and appropriate energy level alignment at the hole-extraction interface, efficiently suppressing recombination loss and enhancing charge collection. Finally, CsPbI3-based PVSCs with IDTT-PhCz as dopant-free HTM achieve a champion power conversion efficiency (PCE) of 21.0 %, which is one of the highest values reported thus far for all-inorganic PVSCs. The optimized device maintains over 90 % of the initial PCE after 500 hours at 60°C, indicating superior thermal stability. Additionally, the CsPbI2Br PVSC based on IDTT-PhCz exhibits an impressive PCE of 18.0 %, and a CsPbI2Br/organic tandem solar cell based on IDTT-PhCz achieves a record-high PCE of 25.0 % (24.66 % certified), which is the highest efficiency among the n-i-p perovskite/organic tandem solar cells to date. Overall, this work demonstrates the superiority and generalizability of the D–A–D’–A–D-type design strategy for achieving efficient PVSCs
A free-standing sulfone-based solid-state electrolyte mitigating the release of crystal water from the Prussian blue cathode for high voltage potassium batteries
No full textPrussian blue (PB) and its analogues are emerging cathode materials for potassium batteries due to their 3D open framework allowing facile ion diffusion. However, the crystal water, an inherent component of PB structure, can be released into the electrolytes especially during high voltage operation, causing detrimental side reactions and rapid degradation of potassium batteries. To address this challenge, we present a free-standing sulfone-based solid-state electrolyte (FSSE) comprising potassium bis(fluorosulfonyl)imide, dimethyl sulfone, and UV-cured trimethylolpropane ethoxylate triacrylate network. The FSSE effectively prevents the release of crystal water from PB cathode while exhibiting suitable electrolyte properties including decent ionic conductivity (2.2 × 10−4 S cm−1 at 25 °C), exceptional oxidative stability (~4.8 V vs. K+/K), and intimate contact with porous composite PB electrodes. K||PB cells utilizing FSSE demonstrate superior cyclability compared to a liquid carbonate electrolyte (74.6% vs 53.3 % capacity retention over 200 cycles). The solid-state electrolyte possessing the ability to block crystal water provides a promising avenue for exploring diverse PB cathode materials for high-voltage potassium batteries