Monthly Archives: September 2023

Electron Transport through Hydrogen Bonded Single‐Molecule Junctions

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Electron Transport through Hydrogen Bonded Single-Molecule Junctions†


Comprehensive Summary

Hydrogen bonding is a vital driving force for organizing the hierarchy of molecular structure, especially in biologic field. Due to its directionality, selectivity and moderate strength, hydrogen bonding has been extensively introduced into the molecular recognition, sensing and electronic devices. Electric measurements at single-molecule level facilitate the investigation of hydrogen bonds and provide a comprehensive understanding of the electron transport properties governed by the hydrogen bonding, which is essential for the development of self-assembled electronic systems. This review provides a detailed overview of recent advancements in constructing single-molecule junctions utilizing intramolecular and intermolecular hydrogen bonding. We first introduce the methods utilized for characterizing the electric and dynamic properties of non-covalent interactions. Next, we discuss the mechanisms of electron transport, relevant influencing factors, and typical applications utilizing electrical signals based on single-molecule junctions. Finally, we propose our perspective on the existing challenges and prospective opportunities in utilizing hydrogen bonding for electronic device applications.

Recent Progress of Inorganic Hole‐Transport Materials for Perovskite Solar Cells

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Recent Progress of Inorganic Hole-Transport Materials for Perovskite Solar Cells†


Comprehensive Summary

Perovskite solar cells (PSCs) have achieved significant progress in the past decade and a certified power conversion efficiency (PCE) of 26.0% has been achieved. The widely used organic hole transport materials (HTMs) in PSCs are typically sensitive to the moisture environment and continuous light exposure. In contrast, the inorganic HTMs benefiting from their outstanding merits, such as excellent environmental stability, are considered as alternatives and have attracted much attention in PSCs. In this review, we provide a comprehensive summary of the fundamental properties and recent progress of inorganic HTMs in n-i-p and p-i-n structured PSCs. Additionally, we emphasize the importance of inorganic HTMs in the development of highly efficient and stable PSCs.

Dual Functional Diblock Amino Acid Copolymer Displaying Synergistic Effect with Curcumin against MRSA and Encapsulation of Curcumin

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Dual Functional Diblock Amino Acid Copolymer Displaying Synergistic Effect with Curcumin against MRSA and Encapsulation of Curcumin†

Dual functional diblock copolymer PLL20-b-PBLG20 was prepared by superfast and water-insensitive polymerization initiated by tetraalkylammonium carboxylate. In addition to direct antimicrobial activity, PLL20-b-PBLG20 also exerts a synergistic bactericidal effect against MRSA with curcumin, a plant extract with antibacterial property. Moreover, PLL20-b-PBLG20 successfully encapsulates curcumin to form nanoparticles via self-assembly. The combination of dual functional PLL20-b-PBLG20 and curcumin holds promise in combating MRSA infections.


Comprehensive Summary

The intensive use of antibiotics intensifies the development of bacterial resistance, which has become a serious problem globally. Methicillin-resistant Staphylococcus aureus (MRSA) has resulted in significant morbidity and mortality. Therefore, it is an urgent need to develop new antimicrobial drugs and administration methods. Herein, we report a dual functional diblock copolymer PLL20-b-PBLG20, which was prepared by superfast and water-insensitive polymerization on N-carboxyanhydrides (NCA) initiated by tetraalkylammonium carboxylate. In addition to direct antimicrobial activity, PLL20-b-PBLG20 also exerts a synergistic bactericidal effect against MRSA with curcumin, a plant extract with antibacterial property. Moreover, PLL20-b-PBLG20 successfully encapsulates curcumin to form nanoparticles via self-assembly. The combination of dual functional PLL20-b-PBLG20 and curcumin holds promise in combating MRSA infections.

Construction of Tumor Microenvironment‐Responsive Gene Carriers

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Construction of Tumor Microenvironment-Responsive Gene Carriers

(EK)10 prevents plasma protein adsorption, and MMP-2-responsive PLGLAG exposes Tat near tumors. A leucine zipper connects (EK)10-PLGLAG-Tat to ELP, creating the environmentally responsive gene carrier (ERGV). ERGV efficiently targets tumors by modifying surface charge in MMP-2 environments, ensuring safe and effective gene delivery.


Abstract

Peptide- and polypeptide-based self-assembling gene delivery systems have received considerable attention owing to their inherent biocompatibility and bioactivity. Gene carriers based on elastin-like polypeptides (ELPs) have been extensively studied because of their controllability and unique temperature responsiveness. The (EK)10-PLGLAG-Tat polypeptide sequence was selected for tumor gene delivery, with ELP serving as the hydrophobic core. In this sequence, a hydration layer can be formed on the surface of the carrier using the zwitterionic peptide segment (EK)10, which helps prevent the nonspecific adsorption of plasma proteins. Additionally, the MMP-2 enzyme-responsive PLGLAG peptide segment is responsible for exposing the cell-penetrating peptide Tat specifically near tumor cells, facilitating the penetration of tumor cells. To introduce (EK)10-PLGLAG-Tat into the self-assembling carrier while ensuring its bioactivity, a leucine zipper ZR/ZE with opposite charges was used to link it to the ELP. Because of its high specificity and low systemic toxicity, the carrier was named environmentally responsive gene carrier (ERGV). Experimental results demonstrated that the ERGV effectively removed (EK)10 in MMP-2 overexpressed environments, altering the surface charge from negative to positive and facilitating ssDNA delivery into tumor cells. These findings highlight the potential of ERGVs as a safe and efficient method for targeted gene delivery to tumors.

Physicochemical and Nonlinear Optical Properties of a Stilbazolium Family Single Crystal with Third Order Nonlinear Optical Activity

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Physicochemical and Nonlinear Optical Properties of a Stilbazolium Family Single Crystal with Third Order Nonlinear Optical Activity

A third-order nonlinear optical 4-[2-(4-dimethylamino-phenyl)-vinyl]-1-methyl-pyridinium 2-nitroaniline-4-sulfonate (DSNA) single crystal was successfully grown for the first time by incorporating a novel counter anion in the stilbazolium cation. Characterization results suggest that the DSNA crystal can be used for optoelectronic and optical limiting applications.


Abstract

A novel counter anion group was incorporated with the organic stilbazolium cation (C16H19N2 +) to yield a new third-harmonic-generation-active single crystal of 4-[2-(4-dimethylamino-phenyl)-vinyl]-1-methyl-pyridinium 2-nitroaniline-4-sulfonate (DSNA). The slow evaporation solution growth technique is employed to obtain DSNA crystals, whose nonlinear responses are analysed through a continuous wave laser Z scan experiment. The thermally induced strong reverse saturation absorption and self-defocusing behaviour of the DSNA crystal suggests that the material could be used as an optical limiting device. Optical characterization shows that the lower absorption edge falls in the visible region (530 nm), with a broad transparency range of 0.53 to 1 μm. Exploration of other optical constants, such as extinction coefficient (k=10−4), emission wavelength (602 nm – red light), optical (σopt=1010 Ωm−1) and electrical conductivity (σelc=1011 Ωm−1) also concludes that the DSNA crystal could be potentially employed in optoelectronic devices. The various bonds and their corresponding lengths and angles involved in the formation of DSNA ionic crystal are evaluated by means of single-crystal X-ray diffraction (SCXRD). Linear and nonlinear optical property findings undoubtedly affirm that the titular DSNA crystal is an effective nonlinear optical (NLO) crystal.

The Importance of Precise Reaction Condition Control for the Comparison of Photocatalyst Materials on the Example of Hydrogen Peroxide Formation over Polymeric Carbon Nitrides

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The Importance of Precise Reaction Condition Control for the Comparison of Photocatalyst Materials on the Example of Hydrogen Peroxide Formation over Polymeric Carbon Nitrides

Our study uses the photocatalytic production of hydrogen peroxide by various polymeric carbon nitride materials to demonstrate the importance of precisely adjusting various reaction conditions in the reactor, such as light intensity, oxygen flow, and wavelength. In addition, reaction parameters were chosen to achieve extremely high hydrogen peroxide concentrations.


Abstract

In our study, we aimed to show how different reaction parameters can affect production rates using photocatalytic hydrogen peroxide formation by different polymeric carbon nitrides (PCN). For this purpose, selected materials were first compared under the same reaction conditions and compared with TiO2 (P25). We also show that different light intensities can have a different influence on seemingly similar materials. Since hydrogen peroxide production in the presence of an electron donor proceeds mainly by reduction of oxygen, we also show an influence of the oxygen flow on the formation rates. Thus, with high oxygen fluxes and high intensities of irradiated light, we were able to achieve an H2O2 concentration of 125 mM after about 25 h. Finally, the two best PCN materials were selected to measure light intensity dependence at different wavelengths up to visible light. It was found that they behaved differently at the different wavelengths and thus it could be shown that an exact specification of the reaction parameters is indispensable for comparisons in the literature.

Garcinolic Acid Distinguishes Between GACKIX Domains and Modulates Interaction Networks

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Garcinolic Acid Distinguishes Between GACKIX Domains and Modulates Interaction Networks

Garcinolic acid is a topologically complex natural product derived from Garcinia hanburyi. It engages the KIX domain in the master coactivator CBP/p300 selectively over other closely related motifs and in doing so disrupts CBP/p300 KIX protein-protein interactions. In the cellular context this enables downregulation of transcriptional circuits essential for cMyb-dependent leukemias.


Abstract

Natural products are often uniquely suited to modulate protein-protein interactions (PPIs) due to their architectural and functional group complexity relative to synthetic molecules. Here we demonstrate that the natural product garcinolic acid allosterically blocks the CBP/p300 KIX PPI network and displays excellent selectivity over related GACKIX motifs. It does so via a strong interaction (K D 1 μM) with a non-canonical binding site containing a structurally dynamic loop in CBP/p300 KIX. Garcinolic acid engages full-length CBP in the context of the proteome and in doing so effectively inhibits KIX-dependent transcription in a leukemia model. As the most potent small-molecule KIX inhibitor yet reported, garcinolic acid represents an important step forward in the therapeutic targeting of CBP/p300.

Caulobacter segnis Dioxygenase CsO2: A Practical Biocatalyst for Stilbenoid Ozonolysis

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Caulobacter segnis Dioxygenase CsO2: A Practical Biocatalyst for Stilbenoid Ozonolysis

The Caulobacter segnis dioxygenase has been employed for the enzymatic alkene cleavage of several stilbenoids, thus generating the corresponding aldehydes. CsO2-mediated ozonolysis represents a greener, safer, and more selective process with respect to conventional chemistry. To further assess the CsO2 usability as a preparative biocatalyst, a 50–mL scale biotransformation of resveratrol has been carried out obtaining the corresponding aldehydes with excellent yields (98 %), rapid reaction times (1.5 h) and unprecedented substrate-to-catalyst ratio (5 103).


Abstract

Ozonolysis is a useful as well as dangerous reaction for performing alkene cleavage. On the other hand, enzymes are considered a more sustainable and safer alternative. Among them, Caulobacter segnis dioxygenase (CsO2) known so far for its ability to catalyze the coenzyme-free oxidation of vinylguaiacol into vanillin, was selected and its substrate scope evaluated towards diverse natural and synthetic stilbenoids. Under optimized conditions, CsO2 catalyzed the oxidative cleavage of the C=C double bonds of various trans-stilbenes, providing that a hydroxyl moiety was necessary in para-position of the phenyl group (e. g., resveratrol and its derivatives) for the reaction to take place, which was confirmed by modelling studies. The reactions occurred rapidly (0.5–3 h) with high conversions (95–99 %) and without formation of by-products. The resveratrol biotransformation was carried out on 50–mL scale thus confirming the feasibility of the biocatalytic system as a preparative method.

Synergistic Effect Enhancing Baeyer‐Villiger Oxidation Performance of Resin‐Derived‐Carbon Supported FeCe Bimetallic Catalyst

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Synergistic Effect Enhancing Baeyer-Villiger Oxidation Performance of Resin-Derived-Carbon Supported FeCe Bimetallic Catalyst

Benefiting from the synergistic effect of supported bimetallic CeFe which induces higher metal dispersion and higher content of reactive oxygen, and the buffering effect of resin-derived-carbon on free radicals, the aerobic oxidation of cyclohexanone to ϵ-caprolactone (ϵ-CL) is performed over CeFe@RDC-x, and the catalytic efficiency is significantly improved. Especially, when solvent-free and green solvents (such as ethyl acetate) are used, excellent catalytic conversion effects are achieved.


Abstract

Upgrading cyclohexanone to ϵ-caprolactone (ϵ-CL) is of great importance to the synthesis of high value-added downstream chemicals and the reduction of foam plastic. The catalytic synthesis of ϵ-CL from cyclohexanone through O2/aldehyde method is an environmentally benign one-pot tandem reaction without using peroxy acid, balancing the requirements of safety and efficiency. However, due to lack of elaborate design and collaboration of multiple active sites for catalysts, the catalytic efficiency of O2/aldehyde method still remains to be improved. Herein, a pitaya-like catalyst (CeFe@RDC-3) with Ce and Fe highly dispersed on resin-derived-carbon is synthesized through high temperature self-assembly. On this bimetallic catalyst, high yield (97 %) of ϵ-CL is achieved through aerobic oxidation of cyclohexanone with only 1.5 equivalent benzaldehyde. Moreover, considerable yields of ϵ-CL, 88.3 % and 74.7 %, respectively, are also obtained over CeFe@RDC-3 with green solvent (EtOAc) or even without solvent. No loss of activity is observed after five successive cycles, demonstrating high stability of CeFe@RDC-3. The mechanism study reveals that the high performance of CeFe@RDC-3 is ascribed to the Ce−Fe bimetallic synergy, uniform metal dispersion, abundant active oxygen and stabilizing effect of resin-derived-carbon to free radicals. This work provides prospect for a green, safe and low-cost strategy for Baeyer-Villiger process.

Engineering an O‐methyltransferase for the Regioselective Biosynthesis of Hesperetin Dihydrochalcone

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Engineering an O-methyltransferase for the Regioselective Biosynthesis of Hesperetin Dihydrochalcone

Engineering enhanced regioselectivity: Directed evolution of an O-methyltransferase resulted in variants with increased regioselectivity for the para-methylation of dihydrochalcones and related catecholic compounds (regioisomeric ratio up to 99 : 1). This allows now the biocatalytic production of the taste active hesperetin dihydrochalcone.


Abstract

Directed evolution of the O-methyltransferase ZgOMT from Zooshikella ganghwensis focusing on active site residues resulted in highly regioselective biocatalysts (regioisomeric ratios up to 99 : 1) for the preparation of the taste active hesperetin dihydrochalcone and related compounds. These newly constructed enzyme variants provide an attractive synthesis route for para-methylation of catechol scaffolds, which is challenging to perform with high regioselectivity utilizing wild-type O-methyltransferases.