Metabolite profiling reveals comprehensive effects of Chaetomium globosum on citrus preservation.

The huge economic loss of citrus fruit after harvest called for safe and efficient preservatives, as chemically synthesized agents threatened the environment and human health. Herein a biocontrol fungus Chaetomium globosum QY-1 near the orchard in riparian area was identified to have antimicrobial, antioxidant and tyrosinase inhibition activity, which meets the requirements of an ideal preservative. Metabolite profiling based on bioassay-guided fractionation was carried out, and eight polyketones were determined by MS and NMR. The most abundant CheA exhibited strong inhibition to Penicillium digitatum, the main pathogen caused citrus fruit rot. Among these metabolites, Epicoccone and Epicoccolide B showed higher antioxidant activity, while Epicoccone and CheA had higher tyrosinase inhibitory activity. All the activities were close to or even better than the positive control (Vc; glutathione; Vc and arbutin; Bellkute), implying that the metabolites of C. globosum had comprehensive effects as natural preservatives.

Sanxiapeptin, a linear pentapeptide from Penicillium oxalicum, inhibited the growth of citrus green mold.

Penicillium oxalicum has been used as a biocontrol fungus in agriculture for many years, but the antimicrobial substances are still uncertain. Herein, we isolated a linear peptide named Sanxiapeptin in the culture broth of Penicillium oxalicum SG-4 collecting from the Three Gorges riparian zone. Sanxiapeptin exhibited potent inhibitory effect on citrus green mold Penicillium digitatum, the main fungi responsible for postharvest decay. Sanxiapeptin was elucidated as composing of five amino acids, which were ß-amino-α-methoxybutyric acid (Amoba), N-Me-l-Thr, d-Thr, N-Me-l-Val and l-Ser. By analyzing three chemically synthesized oligopeptides with similar structures, we found that the first amino acid of Amoba was crucial to the antifungal activity, as was the methylation of peptide bond. Sanxiapeptin may act as an antimicrobial agent by affecting the function of cell membranes or walls. The antimicrobial spectrum, safety and stability analysis supported that Sanxiapeptin was a promising antifungal agent for citrus preservation.

Chiral Os(II) Polypyridyl Complexes as Enantioselective Nuclear DNA Imaging Agents Especially Suitable for Correlative High-Resolution Light and Electron Microscopy Studies.

The high-resolution technique transmission electron microscopy (TEM), with OsO4 as the traditional fixative, is an essential tool for cell biology and medicine. Although OsO4 has been extensively used, it is far from perfect because of its high volatility and toxicity. Os(II) polypyridyl complexes like [Os(phen)2(dppz)]2+ (phen = 1,10-phenanthroline; dppz = dipyridophenazine) are not only the well-known molecular DNA "light-switches" but also the potential ideal candidates for TEM studies. Here, we report that the cell-impermeable cationic [Os(phen)2(dppz)]2+ can be preferentially delivered into the live-cell nucleus through ion-pairing with chlorophenolate counter-anions, where it functions as an unparalleled enantioselective nuclear DNA imaging reagent especially suitable for correlative light and electron microscopy (CLEM) studies in both living and fixed cells, which can clearly visualize chromosome aggregation and decondensation during mitosis simultaneously. We propose that the chiral Os(II) polypyridyl complexes can be used as a distinctive group of enantioselective high-resolution CLEM imaging probes for live-cell nuclear DNA studies.

Protective effect of tomatine against hydrogen peroxide-induced neurotoxicity in neuroblastoma (SH-SY5Y) cells.

OBJECTIVES: Reactive oxygen species can induce cell apoptosis, and oxidative stress has been implicated in a variety of neurodegenerative disorders. Tomatine, which is a naturally occurring steroidal glycoalkaloid isolated from Solanum cathayanum, has shown potent anti-oxidant properties. METHODS: In this study, we used the SH-SY5Y cell line as an in vitro model and investigated the protective effect of tomatine against hydrogen peroxide (H2 O2 )-induced neurotoxicity in SH-SY5Y cells. KEY FINDINGS: Tomatine might inhibit the release of cellular lactate dehydrogenase, increase anti-oxidant enzyme activity and glutathione content, reverse the downregulated protein expression of the brain-derived neurotrophic factor (BDNF), inhibit expression of Bax and activations of caspase-3 and caspase-9 in H2 O2 -induced SH-SY5Y cells. CONCLUSIONS: Tomatine exerted beneficially neuroprotective effect on H2 O2 -induced SH-SY5Y cells, mainly enhancing intracellular anti-oxidant enzyme activity and BDNF expression, inhibiting H2 O2 -induced oxidative stress as well as expression of Bax and activations of caspase-3 and caspase-9, alleviating H2 O2 -induced SH-SY5Y cell injury and cell death.

Tupisteroide A-C, three new polyhydroxylated steroidal constituents from the roots of Tupistra chinensis.

Three new steroidal compounds with polyhydroxy groups, tupisteroide A-C (1-3), were obtained from the roots of Tupistra chinensis, together with one known compound (4) that was isolated from this plant for the first time. The structures of tupisteroide A-C were determined on the basis of one- and two-dimensional NMR spectroscopy, including (1) H-(1) H Correlation Spectroscopy, Heteronuclear Multiple Bond Correlation, and Heteronuclear Single Quantum Coherence experiments. The isolated compounds were evaluated for their cytotoxic activities against A549, HepG2, and CaSki cancer cell lines in vitro. Among them, compounds 1, 2, and 4 did not show significant inhibitory activity, but compound 3 showed cytotoxicity against A549 cancer cell lines with IC(50) values of 25.0 µM.

Five new furostanol saponins from the rhizomes of Tupistra chinensis.

Five new furostanol saponins (1-5), together with three known compounds (6-8) were obtained from the n-butanol soluble fraction of ethanol extract from Tupistra chinensis. Their structures were determined on the basis of chemical methods and spectral data. The isolated compounds were tested in vitro for their cytotoxic activities against the A549, HepG 2 and Caski cancer cell lines. Among them, compounds 6, 7, and 8 showed cytotoxicity against A549 cancer cell lines with IC(50) values of 6.6, 6.7 and 29.1 µM, respectively.

[Research progress in ARF-GEF gene family].

ARF-GEFs are a family of guanine-nucleotide exchange factors catalyzing the exchange of GDP for GTP on ADP-ribosylation factor. Large ARF-GEFs are highly conserved in all eukaryotes. It is an important regulator in both membrane dynamics and protein trafficking. Significant progress has been made in elucidating the structure, subcellular localization, and physiological functions of ARF-GEFs as a hot topic of cell biology recently. In this review, the character-istics and distribution of ARF-GEFs in different species, and recent research progress of ARF-GEFs and their regulation system are summarized.

Fundamental studies on the intermediate layer of a bipolar membrane V. Effect of silver halide and its dope in gelatin on water dissociation at the interface of a bipolar membrane.

The effect of silver ions on the water dissociation of bipolar membranes was first investigated in this paper. To do this, the bipolar membranes were prepared by immersing the anion exchange layers in an AgNO3 solution and then coating a solution of sulfonated polyphenylene oxide (SPPO) on the anion exchange layers. XPS and AES observations indicated that silver at the intermediate layer was in the form of AgCl. The experimental results proved that AgCl has an excellent catalytic function for water dissociation in terms of I-V curves, and the quantity of AgCl played an important role in the behavior of a bipolar membrane. The bipolar membranes with gelatin and the gelatin doped with silver as a catalytic layer were also prepared in the same way, and their I-V behavior and the water dissociation pilot tests were also investigated. The experimental results showed that in the case of gelatin alone, the voltage drop increased slightly at high gelatin concentrations, due mainly to the steric effect and electrostatic interaction, but decreased at low gelatin concentrations due to the hydrophilicity. However, when gelatin was doped with AgCl, the bipolar membranes have an appreciable improvement in both stability and catalytic function, in comparison with those prepared from silver or gelatin.

Fundamental studies on the intermediate layer of a bipolar membrane part IV. Effect of polyvinyl alcohol (PVA) on water dissociation at the interface of a bipolar membrane.

This paper investigates the effect of polyvinyl alcohol (PVA) as the intermediate layer of bipolar membranes on water dissociation. The bipolar membranes are prepared by coating a solution of sulfonated polyphenylene oxide (SPPO) on the anion exchange layers, which had been immersed in PVA aqueous solutions with different concentrations in advance. The experimental results show that the effect of PVA on water dissociation is significantly affected by its concentration: at low concentration range PVA solution catalyzes water dissociation and at high concentration range PVA solution shows a retardant effect. The phenomenon is different from the situation where polyethylene glycol (PEG) is used as the intermediate layer. Based on the adsorption data and the measurements of X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy, it is found that (1) the effect of PVA concentration on water dissociation can be explained by the competition and compromise of two effects--the catalytic and hydrophilic effect of the PVA molecule and the steric effect of the enlargement of junction thickness; (2) the reason that at high concentration range PVA and PEG show different effects on water dissociation is that the junction thickness is enlarged excessively by PVA, which is based on the intrinsic characteristics of PVA molecules.