Latest ArticlesSpin properties of organic molecules have attracted great interest for their potential applications in spintronic devices and quantum computing. Fe-tetraphenyl porphyrin (FeTPP) is of particular interest for its robust magnetic properties on metallic substrates. FeTPP is prepared in vacuum via on-surface synthesis. Molecular structure and spin-related transport properties are characterized by low-temperature scanning tunneling microscope and spectroscopy at 0.5 K. Density functional theory calculations are performed to understand molecular adsorption and spin distribution on Au(111). The molecular structure of FeTPP is distorted upon adsorption on the substrate. Spin excitations of FeTPP are observed on the Fe atom and high pyrrole groups in differential conductance spectra. The calculated spin density distribution indicates that the electron spin of FeTPP is mainly distributed on the Fe atom. The atomic transmission calculation indicates that electrons transport to substrate is mediated through Fe atom, when the tip is above the high pyrrole group.
Two chimeric sesterterpene synthases (AaTPS1 and AaTPS2) were functionally characterized from Alternaria alternata MB-30 isolated from the leaves of a sesterterpenoid-producing Lamiaceae plant Leucosceptrum canum. AaTPS1 generated a 5/8/6/5 tetracyclic sesteraltererol (1) and its absolute stereochemistry was determined by X-ray crystallographic analysis of its derivative 10, 11-epoxysesteraltererol (2), which enabled revision of the absolute configuration of C7 of sesterfisherol produced by NfSS and PTTS014 characterized previously and its derivative 10, 11-epoxysesterfisherol. AaTPS2 produced a 5/15 bicyclic preterpestacin I (3). Site-directed mutagenesis suggested that F192 in AaTPS1 was likely involved in controlling of the hydroxylation of C12, and eight amino acids were important for the enzyme activity of AaTPS1 and AaTPS2. The engineered Escherichia coli and Saccharomyces cerevisiae strains were constructed for the productions of compounds 1 and 3, and the highest titer of compound 1 reached 62.3 mg/L in shake-flask culture. Both compounds 1 and 2 showed anti-adipogenic activity.
Plaque plays a central role in atherosclerosis (AS) progression, whereas inflammation and destruction of the plaque microenvironment contribute to plaque advancement. As a result, a therapy regime, which combines anti-inflammation and inhibition-degradation of plaque matrix, appears to be a promising strategy to combat AS. Herein, we report a pH-sensitive liposome co-loading with the anti-inflammatory agent (oridonin, ORD) and plaque-collagen protector (marimastat) for anti-AS therapy. ORD was first conjugated with hyaluronic acid (HA) to target the inflammation contributor, pro-inflammatory macrophages. Then, the conjugate assembled onto the MATT-loaded liposomes. The co-loaded system (~150 nm) significantly improved pharmacokinetics over the liposomes without anchoring the conjugate and accumulated effectively in the plaque. The preparation administration allowed efficient anti-AS activities in high-fat diet (HFD)-Apoe-/- mice by decreasing the pro-inflammatory cytokine expression in the serum, lessening the lesion area, alleviating the plaque collagen degradation, promoting macrophage polarization from phenotypic M1 to M2, reducing T helper (Th) 17 cells (Th17)/T regulatory cells (Tregs) and Th1/Th2 ratio, etc. Furthermore, the serum determination in AS patients demonstrated high expression of the inflammatory cytokines, indicating our finding may offer a potential guideline for clinical practice.
Allenylboronates represent a very intriguing class of organoborons but are challenging to synthesis. In addition, these compounds are typically unstable, rendering the separation difficult. We report herein a practical and concise route to a new class of stable, easy-separable allenyl B(MIDA) via a hydrazination/fragmentation of B(MIDA)-propargylic alcohols. The synthesis of optically active allenyl B(MIDA) was also achieved. Interesting reactivity of the resulting product was observed.
The fabrication of highly effective photosensitizers has received considerable attention because of their attractive functions and applications in the fields of photodynamic therapy, photosynthesis, photocatalysis, etc. Thus, it is highly desirable to develop a new approach to enhance photosensitization efficiency. Herein, through coordination-driven self-assembly, a series of metallacycles with efficient fluorescence resonance energy transfer (FRET) were effectively constructed, which displayed higher photosensitization efficiency and photocatalytic activity than their model metallacycles without FRET due to broadband absorption and singlet energy transfer from the energy acceptor to the energy donor. Moreover, iodization of fluorophores induced a significant enhancement of the photosensitization efficiency and photocatalytic activity of the metallacycles. This research provides an efficient strategy for improving photosensitization efficiency and a promising platform for the preparation of effective photosensitizers and photocatalysts.
Gambogic acid (GA) is a potential clinical anticancer drug that can exert antitumor effects via various molecular mechanisms. Notwithstanding, GA's low water solubility, poor stability, short half-life, and unavoidable toxic side effects have significantly hampered its clinical application. Erythrocyte membrane-coated nanoparticles (RBCM-NPs) improve drug's physicochemical properties, biocompatibility, and pharmacokinetic behaviors, allowing for long-term drug circulation and passive targeting. In this study, a novel biomimetic drug delivery system (DDS) against hepatocellular carcinoma was prepared by covering RBCM on GPP-NPs (GA-loaded mPEG-PLA NPs) to develop the RBC@GPP-NPs. In comparison to RBCM-free nanoparticles and free GA, RBC@GPP-NPs improved the drug's water solubility, stability, safety, and anti-tumor activity in vivo. We expect that this bionic nanoparticle composite can expand the clinical applicability of GA and provide a feasible solution for the research and development of GA's nano-formulation.
Stability of liposomes plays a crucial role in drug delivery, especially in oral aspect. The structural modification of liposomes has been the orientation of efforts to improve their stability and enable the controllability of payload release. This study reported a selenylation strategy to optimize the liposomal structure in an attempt to enhance the nanocarrier's stability, hence the bioavailability of emodin (EM), an active compound with poor water-solubility. EM-loaded selenized liposomes (EM-Se@LPs) were prepared by thin film dispersion followed by in situ reduction technique. The results showed that EM-Se@LPs were provided with enhancive gastrointestinal stability and exhibited sustained release of drug compared with EM-loaded liposomes (EM-LPs). However, the modified liposomes with Se depositing onto the interior and exterior bilayers did not substantially facilitate absorption of EM. The reinforced structure of liposomes irrelevant to absorption was affirmed to be due to good stability and absorbability of EM itself. Nevertheless, the present work provides an alternative option for stabilization of liposomes instead of conventional methods, which may be promising for oral delivery of physiologically unstable and/or poorly absorbed drugs and systemic drug delivery.
In this paper, supra-amphiphilic compounds containing disaccharides and azobenzene ends have been constructed via dynamic covalent bond. It was found that the slight structural difference of the disaccharides made significant difference in the self-assembled morphologies. Namely, three kinds of azo-disaccharide supra-amphiphiles were found to assemble into different morphologies, with the only difference in chemical structure from the disaccharides. More importantly, the structural difference between the disaccharides, including lactoside, maltoside and cellobioside was trivial. Molecular simulation revealed the packing of molecules was due to the different contribution from hydrogen bonds. The above results clearly indicated the contribution of saccharide packing, especially the related hydrogen bonding, to the final morphology of the assembled structures.
An N-heterocyclic carbene (NHC)-catalyzed carbonyl nucleophilic substitution reaction between 1-cyclopropylcarbaldehydes and N-sulfonyl imines is developed for access to linear β-aminoenone products. The β-aminoenones containing cyclopropyl fragments can be afforded in moderate to excellent yields under mild conditions. The reaction features excellent trans-diastereoselectivities and the desired aminoenone products are all afforded as Z-isomers.
Repeated waves of influenza virus H7N9 epidemics after 2013 have caused severe influenza in humans, with mortality reaching approximately 40%–50%. To prevent possible pandemics, the development of highly effective vaccines against influenza virus H7N9 is highly desired. In the present study, by taking advantage of the d-tetra-peptide adjuvant (GDFDFDY), we reported a simple method to prepare H7N9 vaccines. Naproxen (Npx), with good anti inflammatory and broad anti-viral effects, was employed as an N-terminal capping group to construct a hydrogel precursor, Npx-GDFDFDY. The hydrogel adjuvant was prepared using a routine heating cooling protocol and the final vaccine was ready after mixing with the split A/Zhejiang/DTID-ZJU01/2013 (H7N9) antigen by vortexing. Compared with the traditional Al(OH)3 adjuvant vaccine and the split vaccine, our hydrogel adjuvant vaccine showed the best preventive effects against H7N9 infection. A mechanistic study illustrated that higher antibody responses and variations in cytokine expression might account for its increased protective effects. Our strategy demonstrated the advantages of a peptide hydrogel adjuvant in the application of vaccines against H7N9 and demonstrated its potential application in vaccines against emerging threats from other viruses.
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