Biosynthesis of arachidonic acid in the oleaginous microalga Parietochloris incisa (Chlorophyceae): Radiolabeling studies

The fresh-water green alga Parietochloris incisa is the richest plant source of the PUFA arachidonic acid (20∶4n−6, AA). To elucidate the biosynthesis of AA in this alga we labeled cultures of P. incisa with radioactive precursors. Pulse chase labeling with acetate resulted in its incorporation via the de novo biosynthesis pathway of FA. However, labeled acetate was also utilized for the elongation of C₁₆ and C₁₈ PUFA. Labeling with [1-¹⁴C]oleic acid has shown that the first steps of the lipid-linked FA desaturations utilize cytoplasmic lipids. PC and diacylglyceryltrimethylhomoserine are the major lipids involved as acyl carriers for the Δ12 and Δ6 desaturations of oleic acid, leading sequentially to linoleic and γ-linolenic acids. The latter is released from its lipid carrier and elongated to 20∶3n−6, which is reincorporated primarily into PF and PC and finally desaturated to AA. Galactolipids, mostly monogalctosyldiacylglycerol (MGDG), serve as substrates for the chloroplastic Δ12 desaturase and, apparently, the ω3 desaturation, common to higher plants and many green algae. The predominant sequence desaturates the 18∶1/16∶0 molecular species of MGDG stepwise to the 18∶3n−3/16∶3n−3 molecular species similar to the prokaryotic pathway of higher plants and green algae.     

Identification of Highly Potent Protein Kinase C‐Related Kinase 1 Inhibitors by Virtual Screening,Binding Free Energy Rescoring,and in vitro Testing

Despite the considerable interest in protein kinase C‐related kinase 1 (PRK1) as a target in cancer research, there is still a lack of PRK1 inhibitors with suitable selectivity profiles and physicochemical properties. To identify new PRK1 inhibitors we applied a virtual screening approach, which combines ensemble docking, minimization of the protein–ligand complex, binding free energy calculations, and application of quantitative structure–activity relationship (QSAR) models for predicting in vitro activity. The developed approach was then applied in a prospective manner to screen available libraries of kinase inhibitors from Selleck and GlaxoSmithKline (GSK). Compounds that showed favorable prediction were then tested in vitro for PRK1 inhibition. Some of the hits were found to inhibit PRK1 in the low‐nanomolar range. Three in vitro hits were additionally tested in a mass‐spectrometry‐based cellular kinase profiling assay to examine selectivity. Our findings show that nanomolar and drug‐like inhibitors can be identified by the virtual screening approach presented herein. The identified inhibitors are valuable tools for gaining a better understanding of PRK1 inhibition, and the identified hits can serve as starting points for further chemical optimization.     

Dealing with Zero Flows in the Simulation of Water Distribution Networks with Low-Resistance Pipes Using the Global Gradient Algorithm

Water Resources Management - This paper shows that the zero flow treatment algorithm and the convergence criteria of EPANET 2.2, the latest version of the EPANET 2 open-source software package, may...     

A single center,open‐label,randomized, parallel group study assessing the relationship between asymptomatic bacteriuria and inflammation in maintenance hemodialysis patients

Introduction: The significance of asymptomatic bacteriuria in maintenance hemodialysis (MHD) patients remains controversial. We hypothesized that the presence of asymptomatic bacteriuria as a sole clinical manifestation of urinary tract infection (UTI) in asymptomatic MHD patient may contribute to the chronic inflammatory response. Our aim was to explore the relationship between asymptomatic bacteriuria and elevated levels of inflammatory markers in MHD patients. Methods: A randomized open‐label single center study of 114 MHD patients was conducted. Forty‐six patients presented negative urine culture and 41 subjects were excluded due to different reasons. The remaining 27 patients (mean age of 71.5 ± 12.2 years, 63% men), fulfilling the criteria for having asymptomatic bacteriuria, were randomly assigned to either the treatment group (13 patients) or the observational group (14 subjects). The treatment group received 7 days of antibiotic treatment given according to bacteriogram sensitivity. After 3 months of follow‐up all measurements of the study were repeated. The primary end point was change in inflammatory biomarkers from baseline by the end of the study. Findings: There were no statistically significant differences in white blood cell changes (P = 0.27), ferritin (P = 0.09), C‐reactive protein (P = 0.90), and interleukin‐6 (P = 0.14) levels between the groups from baseline to the end of study or at the end of the study. Analyzing cross‐sectional data, asymptomatic bacteriuria was found to not be a predictor of higher levels of inflammatory parameters at baseline. Discussion: Asymptomatic bacteriuria is not a modifiable risk factor for chronic inflammation in the MHD population.     

Formation of branched polyethylenes by ethylene homopolymerization using LNiBr2 homo- and heterogeneous precatalysts: Interpretation of the polymer structures in comparison with commercial LLDPE

Comparative data on the micro-structures and properties of branched polyethylenes (BPE) produced via ethylene homopolymerization over homogeneous N,N-α-diimine LNiBr₂ complexes with different ligand composition (AlEt₂Cl as a cocatalyst) and corresponding supported catalysts LNiBr₂/SiO₂(Al) (Al[iso-Bu]₃ as a cocatalyst) are presented. Noticeable differences were observed between micro-structures of BPEs obtained using homo- and heterogeneous LNiBr₂ complexes as catalysts. Supported catalysts produce BPEs with the majority of methyl branches (17–18 CH₃(1000 C)⁻¹ characterized by different molecular masses (1800–210 kg mol⁻¹) and molecular weight distributions (M_w[M_n]⁻¹ = 5.9 and 2.6). Thermal and mechanical properties of these BPE samples obtained over supported Ni catalysts are similar to those of commercial LLDPE samples prepared with metallocene and Ziegler-Natta catalysts.     

Reactive Surfactants for Achieving Open-Cell PolyHIPE Foams from Pickering Emulsions

PolyHIPEs, highly porous polymers synthesized within high internal phase emulsions (HIPEs), emulsions with over 74% internal phase, are of interest for applications such as absorbents, reaction supports, and tissue engineering scaffolds. Typically, the surfactant contents for HIPE stabilization are relatively high, ranging from 20 to 30 wt% of the external phase, with the monomers usually being the remainder. One drawback of using surfactants for these applications is the potential for leachables, necessitating intensive purification processes for their removal. Pickering HIPEs, HIPEs stabilized using amphiphilic solid nanoparticles that spontaneously migrate to the oil–water interface, can be used as an alternative HIPE stabilization strategy. Although nanoparticles can add surface functionality advantageous for the application, polyHIPEs from Pickering HIPEs often lack the interconnecting holes needed for the high permeability required for such applications. This work describes a successful approach for designing an HIPE stabilization system that is based on a combination of nanoparticles and reactive surfactants and that generates the desired surface functionality, an interconnected porous structure, and a low leachable content. Such an approach can extend the applicative utility of such polyHIPEs by circumventing the need for extensive purification.     

Cloning and Characterization of the ∆6 Polyunsaturated Fatty Acid Elongase from the Green Microalga <Emphasis Type="Italic">Parietochloris incisa</Emphasis>

The very-long-chain polyunsaturated fatty acid (VLC-PUFA), arachidonic acid (ARA, 20:4ω-6) is a component of neuron tissues such as brain and retina cells and a primary substrate for the biosynthesis of biologically active eicosanoids. The green freshwater microalga Parietochloris incisa (Trebouxiophyceae) has been shown to accumulate an extraordinary high content of ARA-rich triacylglycerols. It was thus interesting to characterize the genes involved in lipid biosynthesis in this alga. We report here the identification of a cDNA encoding for a P. incisa PUFA elongase (PiELO1) and demonstrate that the expression of PiELO1 in yeast Saccharomyces cereviseae confers its elongase activity on C18 ∆6 PUFA. Phylogenetic analysis indicated that PiELO1 is highly similar to functionally characterized ∆6 PUFA elongase genes from other green algae and lower plants. Quantitative real-time PCR expression studies showed that PiELO1 is upregulated under nitrogen starvation, the condition triggering and enhancing storage oil and ARA accumulation in P. incisa.