Synthesis and antioxidant properties of dendritic polyphenols

Three dendritic polyphenols (generation 1) were synthesized: a syringaldehyde-based dendrimer (1), a vanillin-based dendrimer (2), and an iodinated vanillin-based dendrimer (3). They all showed strong antioxidant activity according to the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical assay. The syringaldehyde dendrimer was twice and 10 times stronger than quercetin and Trolox, respectively. The vanillin-based dendrimer and its more hydrophobic iodinated derivative were also more potent antioxidants than quercetin and Trolox. The DPPH order of potency was 1 > 2, 3 > quercetin > Trolox. All three dendrimers also protected human LDL from free radical attack in a dose-dependent manner. Their order of free radical scavenging was 1 > 3 > 2 > quercetin > Trolox. The increased hydrophobic nature of the iodinated derivative may have contributed to its better LDL protection than 2. Protection of linoleic acid oxidation was studied by the β-carotene–linoleate assay. Dendrimer 1 was clearly superior to the other antioxidants in protecting the fatty acid. In case of DNA protection against free radical damage, the order of activity was 1 > quercetin > 2 > 3, Trolox. Pro-oxidant effect on copper-induced DNA oxidation showed the following order: quercetin, Trolox > 1 > 2 > 3. Results of the study show that dendritic antioxidants, even at the generation 1 level, provide promising antioxidant properties for their potential use as drug candidates for diseases associated with oxidative stress.     

Characterization of binding proteins that recognize oligoglucoside elicitors of phytoalexin synthesis in soybean

We are studying the cellular signaling pathway leading to pterocarpan phytoalexin biosynthesis in soybean that is induced by a branched hepta-β-glucoside originally isolated from the mycelial walls of the phytopathogenic oomycete Phytophthora sojae. Our research has focused on the specific recognition of the hepta-β-glucoside elicitor by binding proteins in soybean cells. Elicitor-binding proteins with properties expected of physiological receptors for the hepta-β-glucoside elicitor have been identified in soybean root membranes. These elicitor-binding proteins co-migrate with a plasma membrane marker (vanadate-sensitive H⁺-ATPase) on linear sucrose density gradients. Binding of a radio-iodinated derivative of the hepta-β-glucoside elicitor by membrane-localized elicitor-binding proteins is specific, reversible, saturable, and of high affinity (K_d? 1 nM). After solubilization with the nonionic detergent, n-dodecylsucrose, the elicitor-binding proteins retain their high affinity (K_d= 1.8 nM) for the radiolabeled elicitor and their binding specificity for elicitor-active oligoglucosides. A direct correlation is observed between the ability of oligoglucosides to displace labeled elicitor from the elicitor-binding proteins and the elicitor activity of the oligosaccharides. Thus, the elicitor-binding proteins recognize the same structural elements of the hepta-β-glucoside elicitor that are essential for its phytoalexin-inducing activity, suggesting that the binding proteins are physiological receptors for the elicitor. Current research is directed toward the purification of the hepta-β-glucoside elicitor-binding proteins by using ligand affinity chromatography. Purification and characterization of the hepta-β-glucoside binding proteins are among the first steps toward elucidating how the hepta-β-glucoside elicitor triggers the signal transduction pathway that ultimately leads to the synthesis of phytoalexins in soybean.     

Universal Strategy with Structural and Chemical Crosslinking Interface for Efficient and Stable Perovskite Solar Cells

Due to the limited interface contact and weak interfacial interaction, planar heterojunction perovskite solar cells (PSCs) have space for further improvement. Herein, a structural and chemical crosslinking interface is proposed and constructed by introducing an extra layer, which blends tin dioxide (SnO₂) nanoparticles with chloride salts. Since the incorporated materials can be dissolved during the fabrication of perovskite, the quality of perovskite films is improved, leading to larger grain size and reduced trap-state density. Also, more chloride ions at the SnO₂/perovskite interface are observed and the interaction between Cl⁻ and Sn⁴⁺ is confirmed. It results in more pronounced n-type SnO₂ with better conductivity and deeper conduction bands, leading to preferable energy level alignment between SnO₂ and perovskite. Consequently, the open-circuit voltage and fill factor of the devices increase, and target cells present better stability, retaining 98% of initial efficiencies after >10 000 h storage in dry air (≈5% relative humidity) and maintaining 85.50% of the initial efficiency after 1000 h of operation under light. This strategy enables the achievement of 25.28% efficiency with a low bandgap (1.53 eV) perovskite composition, and it is confirmed to be universal when other related materials are utilized.     

A dominant complement fixation pathway for pneumococcal polysaccharides initiated by SIGN-R1 interacting with C1q

The intricate system of serum complement proteins provides resistance to infection. A pivotal step in the complement pathway is the assembly of a C3 convertase, which digests the C3 complement component to form microbial binding C3 fragments recognized by leukocytes. The spleen and C3 provide resistance against blood-borne S. pneumoniae infection. To better understand the mechanisms involved, we studied SIGN-R1, a lectin that captures microbial polysaccharides in spleen. Surprisingly, conditional SIGN-R1 knockout mice developed deficits in C3 catabolism when given S. pneumoniae or its capsular polysaccharide intravenously. There were marked reductions in proteolysis of serum C3, deposition of C3 on organisms within SIGN-R1(+) spleen macrophages, and formation of C3 ligands. We found that SIGN-R1 directly bound the complement C1 subcomponent, C1q, and assembled a C3 convertase, but without the traditional requirement for either antibody or factor B. The transmembrane lectin SIGN-R1 therefore contributes to innate resistance by an unusual C3 activation pathway.     

Expression and characterization of the integral membrane domain of bacterial histidine kinase SCO3062 for structural studies

Bacterial histidine kinases play an important role in the response to external stimuli. Structural studies of the histidine kinase transmembrane domain are challenging due to difficulties in protein expression and sample preparation. After carrying out expression screening of a series of histidine kinases, we investigated sample preparation methods for obtaining high quality samples of the periplasmic and transmembrane domain (PTD) of the bacterial histidine kinase SCO3062. Various sample conditions were tested for their ability to give homogeneous NMR spectra of the SCO3062 PTD with well-resolved resonances. Circular dichroism and 3D ¹⁵N-edited NOESY spectrum results demonstrate that the SCO3062 PTD is predominantly α-helical. This method should be applicable to the NMR analysis of other transmembrane proteins.     

Association of CHRDL1 Mutations and Variants with X-linked Megalocornea,Neuh?user Syndrome and Central Corneal Thickness

We describe novel CHRDL1 mutations in ten families with X-linked megalocornea (MGC1). Our mutation-positive cohort enabled us to establish ultrasonography as a reliable clinical diagnostic tool to distinguish between MGC1 and primary congenital glaucoma (PCG). Megalocornea is also a feature of Neuhäuser or megalocornea-mental retardation (MMR) syndrome, a rare condition of unknown etiology. In a male patient diagnosed with MMR, we performed targeted and whole exome sequencing (WES) and identified a novel missense mutation in CHRDL1 that accounts for his MGC1 phenotype but not his non-ocular features. This finding suggests that MMR syndrome, in some cases, may be di- or multigenic. MGC1 patients have reduced central corneal thickness (CCT); however no X-linked loci have been associated with CCT, possibly because the majority of genome-wide association studies (GWAS) overlook the X-chromosome. We therefore explored whether variants on the X-chromosome are associated with CCT. We found rs149956316, in intron 6 of CHRDL1, to be the most significantly associated single nucleotide polymorphism (SNP) (p = 6.81×10⁻⁶) on the X-chromosome. However, this association was not replicated in a smaller subset of whole genome sequenced samples. This study highlights the importance of including X-chromosome SNP data in GWAS to identify potential loci associated with quantitative traits or disease risk.     

Synergistic activation of lipopolysaccharide-stimulated glial cells by propofol

Despite the extensive use of propofol in general anesthetic procedures, the effects of propofol on glial cell were not completely understood. In lipopolysaccharide (LPS)-stimulated rat primary astrocytes and BV2 microglial cell lines, co-treatment of propofol synergistically induced inflammatory activation as evidenced by the increased production of NO, ROS and expression of iNOS, MMP-9 and several cytokines. Propofol augmented the activation of JNK and p38 MAPKs induced by LPS and the synergistic activation of glial cells by propofol was prevented by pretreatment of JNK and p38 inhibitors. When we treated BV2 cell culture supernatants treated with LPS plus propofol on cultured rat primary neuron, it induced a significant neuronal cell death. The results suggest that the repeated use of propofol in immunologically challenged situation may induce glial activation in brain.     

Micropropagation of chinese redbud (<Emphasis Type="Italic">Cercis yunnanensis</Emphasis>) through axillary bud breaking and induction of adventitious shoots from leaf pieces

Summary Factors affecting in vitro shoot production and regeneration of Cercis yunnanensis Hu et Cheng were investigated by comparing various growth regulators and explant types. For optimum shoot production from axillary buds, Murashige and Skoog (MS) media containing 6-benzyladenine, either alone or in combination with a low concentration of thidiazuron, resulted in the greatest number of shoots formed per explant (>3). Explants (2 mm long) containing one axillary bud placed in directcontact with the medium yielded the most shoots per bud (1.6) when grown on growth regulator-free medium. Root formation on 70–80% of shoot explants was accomplished using either indole-3-butyric acid or α-naphthaleneacetic acid in the medium, with significantly more roots formed on explants possessing and apical bud than those without the bud. Direct shoot organogenesis from leaf explants occurred on MS medium containing 10–30 μM thidiazuron, with up to 42% of leaf explants producing shoots.