Cloning, sequencing, analysis, and heterologous expression of the fredericamycin biosynthetic gene cluster from Streptomyces griseus

Fredericamycin (FDM) A, a pentadecaketide featuring two sets of peri-hydroxy tricyclic aromatic moieties connected through a unique chiral spiro carbon center, exhibits potent cytotoxicity and has been studied as a new type of anticancer drug lead because of its novel molecular architecture. The fdm gene cluster was localized to 33-kb DNA segment of Streptomyces griseus ATCC 49344, and its involvement in FDM A biosynthesis was proven by gene inactivation, complementation, and heterologous expression experiments. The fdm cluster consists of 28 open reading frames (ORFs), encoding a type II polyketide synthase (PKS) and tailoring enzymes as well as several regulatory and resistance proteins. The FDM PKS features a KSalpha subunit with heretofore unseen tandem cysteines at its active site, a KSbeta subunit that is distinct phylogenetically from KSbeta of hexa-, octa-, or decaketide PKSs, and a dedicated phosphopantetheinyl transferase. Further study of the FDM PKS could provide new insight into how a type II PKS controls chain length in aromatic polyketide biosynthesis. The availability of the fdm genes, in vivo characterization of the fdm cluster in S. griseus, and heterologous expression of the fdm cluster in Streptomyces albus set the stage to investigate FDM A biosynthesis and engineer the FDM biosynthetic machinery for the production of novel FDM A analogues.     

The Influence of Tyrosol-Enriched Rhodiola sachalinensis Extracts Bioconverted by the Mycelium of Bovista plumbe on Scopolamine-Induced Cognitive,Behavioral, and Physiological Responses in Mice

Alzheimer’s disease (AD) is an age-related neurodegenerative disorder characterized by cognitive deficits, which are accompanied by memory loss and cognitive disruption. Rhodiola sachalinensis (RSE) is a medicinal plant that has been used in northeastern Asia for various pharmacological activities. We attempted to carry out the bioconversion of RSE (Bio-RSE) using the mycelium of Bovista plumbe to obtain tyrosol-enriched Bio-RSE. The objective of this study was to investigate the effects of Bio-RSE on the activation of the cholinergic system and the inhibition of oxidative stress in mice with scopolamine (Sco)-induced memory impairment. Sco (1 mg/kg body weight, i.p.) impaired the mice’s performance on the Y-maze test, passive avoidance test, and water maze test. However, the number of abnormal behaviors was reduced in the groups supplemented with Bio-RSE. Bio-RSE treatment improved working memory and avoidance times against electronic shock, increased step-through latency, and reduced the time to reach the escape zone in the water maze test. Bio-RSE dramatically improved the cholinergic system by decreasing acetylcholinesterase activity and regulated oxidative stress by increasing antioxidant enzymes (superoxide dismutase (SOD) and catalase (CAT)). The reduction in nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) signaling in the brain tissue due to scopolamine was restored by the administration of Bio-RSE. Bio-RSE also significantly decreased amyloid-beta 1–42 (Aβ1–42) and amyloid precursor protein (APP) expression. Moreover, the increased malondialdehyde (MDA) level and low total antioxidant capacity in Sco-treated mouse brains were reversed by Bio-RSE, and an increase in Nrf2 and HO-1 was also observed. In conclusion, Bio-RSE protected against Sco-induced cognitive impairment by activating Nrf2/HO-1 signaling and may be developed as a potential beneficial material for AD.     

Fabrication and evaluation of bacterial cellulose-polyaniline composites by interfacial polymerization

The fabrication and evaluation of nanocomposites based on microbial cellulose and polyaniline (PANi) are described. Microbial cellulose, so called, bacterial cellulose (BC) was introduced to interfacial polymerization of aniline. Two different phases based on water and chloroform made it easy for nanosized PANi particles to be synthesized on BC. Without any help of a surfactant or templates, BC played a critical role of supporting the growth of PANi. As a function of aniline concentration, the corresponding PANi content and volume resistivity were checked. From morphological images observed by FE-SEM, PANi nanoparticles were densely arrayed along every fiber of BC. The conjugated backbone of PANi was thought to contribute to the improvements of thermal stability of PANi/BC composites. The stiffness and brittleness of PANi were compensated by more ductile BC, suggesting BC can be a promising substrate for it. By the simple and facile interfacial polymerization, the electrical conductivity of PANi/BC composites reached up to 3.8?×?10^?1?S/cm when 0.32?M of aniline was used. This PANi/BC nanocomposite can be useful in applications requiring biocompatibility and electrical conductivity such as biological and chemical sensors.     

Dimesogenic liquid crystal consisting of cholesterol and Schiff base moieties: dependence of LC properties on the spacer length and fluorination of the alkoxy tails

The liquid crystalline properties of two series of non‐symmetric liquid crystal dimers consisting of cholesterol and Schiff base moieties interconnected by ω‐oxyalkanoyl spacers of varying length are compared: one series (SBOC‐ n ) carry the octyloxy tail on the Schiff base mesogen, and the other (SBOF‐ n ) a perfluoroheptylmethyloxy tail. In general, compounds with the fluorinated alkoxy tail exhibited mesophases over a much wider temperature range than those with the alkoxy tail. The latter series favoured the formation of more diverse mesophases than the former. SBOC‐4, ‐5 and ‐7, and SBOF‐4, ‐5 and ‐10 formed the chiral smectic C phase.     

Quantitative determination of duloxetine and its metabolite in rat plasma by HPLC‐MS/MS

The major metabolite of duloxetine is a glucuronide conjugate of 4‐hydroxy duloxetine (4‐HD). However, interestingly, there have been no reports determining concentrations of 4‐HD and no fully validated method has been established for measuring duloxetine and 4‐HD in rat plasma. We developed a method for the simultaneous quantification of duloxetine and its metabolite in rat plasma using high‐performance liquid chromatography tandem mass spectrometry. Duloxetine and 4‐HD were analyzed on a reverse‐phase C₁₈ analytical column after protein precipitation of the plasma sample with methanol, using carbamazepine as an internal standard. The isocratic mobile phase of 5 mm ammonium acetate–methanol (4:6, v/v) was eluted at 0.4 mL/min. Quantification was performed on a triple‐quadrupole mass spectrometer using electrospray ionization, and the ion transition monitored in selective reaction monitoring mode. The coefficient of variation for assay precision was <18.0%, and the accuracy was 84.0–118.0%. This method was successfully used to measure the concentrations of duloxetine and its metabolite in plasma following the oral administration of a single 40 mg/kg dose in rats. Copyright © 2013 John Wiley & Sons, Ltd.