Natural products studies of the marine cyanobacteria Lyngbya semiplena and Lyngbya majuscula

This thesis details my investigations of marine cyanobacterial natural products that resulted in the discovery of eighteen new secondary metabolites. Isolation and characterization of these unique molecules were carried out using different chromatographic techniques and by careful analyses of 1D and 2D NMR data, respectively. Preliminary bioassays of the crude organic extract of the marine cyanobacterium Lyngbya semiplena collected from Papua New Guinea in 1999, showed good activity in the brine shrimp toxicity model at 10 ppm. Guided by this assay, seven new anandamide-like fatty acid amides, semiplenamides A to G, together with four cyclic depsipeptides, wewakpeptins A to D, were identified. Due to the structural resemblance of the novel ethanolamide derivatives (semiplenamide A-G) with anandamide, (N-arachidonoyl-ethanolamine), an endogenous agonist of cannabinoid receptors compounds, semiplenamide A-G were tested on the well characterized proteins of the endocannabinoid system: 1) the "central" cannabinoid CB₁ receptors; 2) the anandamide membrane transporter (AMT), which is responsible for anandamide cellular uptake; and 3) the fatty acid amide hydrolase (FAAH), which catalyses anandamide hydrolysis. Three showed modest potency in displacing radiolabeled anandamide from the cannabinoid receptor (CB₁), and one was a modest inhibitor of the anandamide membrane transporter (AMT). The wewakpeptins were tested for cytotoxicity to NCI-H460 human lung tumor and neuro-2a mouse neuroblastoma cells. Intriguingly, wewakpeptin A and B were approximately 10-fold more toxic than C and D to these cell lines. Lyngbya majuscula has been recognized as a chemically and biologically rich strain. Five new lyngbyabellin analogs, lyngbyabellins E-I, along with the known compound dolabellin, originally isolated from sea hare Dolabella auricularia, were identified from a 2002 Papua New Guinea collection of the marine cyanobacterium Lyngbya majuscula. The lyngbyabellins were tested for cytotoxicity to NCI-H460 human lung tumor and neuro-2a mouse neuroblastoma cells and had LC₅₀ values between 0.2 and 4.8 μM. Intriguingly, lyngbyabellin E and H appeared to be more active against the H460 cell line with LC₅₀ values of 0.4 μM and 0.2 μM, respectively, compared to LC₅₀ values of 1.2 and 1.4 μM in the neuro-2a cell line. Lynbyabellin I was the most toxic to neuro-2a cells (LC₅₀ 0.7 μM), whereas lyngbyabellin G, was the least cytotoxic of all compounds to either cell line. On the basis of this limited screening, it appears that lung tumor cell toxicity is enhanced in the cyclic representatives, and overall potency is increased in those containing an elaborated side chain. Additionally, two new cytotoxins, aurilides B and C, which are closely related to aurilide, originally isolated from the sea hare Dolabella auricularia, have been identified from the same extract where the lyngbyabellins E-I were isolated. Aurilides B and C were tested for cytotoxicity to NCI-H460 human lung tumor and neuro-2a mouse neuroblastoma cells. Interestingly, aurilide B was approximately 4-fold more toxic than C to these cell lines. The LC₅₀ for Aurilide B was 0.01 μM and 0.04 μM for neuro-2a and H460 cells, respectively, and 0.05 μM and 0.13 μM, respectively, for aurilide C. Aurilide B was evaluated in the NCI 60 cell line panel and found to exhibit a high level of growth inhibition in leukemia, renal, and prostate cancer cell lines with a GI₅₀ less than 10 nM. Aurilide B showed net tumor cell killing activity in the NCI's hollow fiber assay, an in vivo model for assessing a chemical's anticancer activity

The Spatial Correlation Analysis of China's Regional R&D Technical Efficiency

The paper uses SFA technique to measure the regional R&D technical efficiency in China during 1999~2008, applies spatial measurement economics technique to analyze the correlation and convergence characteristics, and builds a spatial convergency model to analyze the spatial convergency characteristics of the regional R&D technical efficiency. The analysis result shows that there appears positive correlation characteristic and an absolute convergence trend on the regional R&D technical efficiency in China, and the effect of spatial geographical factors on the regional R&D technical efficiency is significant

Assembly of lipase and P450 fatty acid decarboxylase to constitute a novel biosynthetic pathway for production of 1-alkenes from renewable triacylglycerols and oils

<p> Background: Biogenic hydrocarbons (biohydrocarbons) are broadly accepted to be the ideal &#39;drop-in&#39; biofuel alternative to petroleum-based fuels due to their highly similar chemical composition and physical characteristics. The biological production of aliphatic hydrocarbons is largely dependent on engineering of the complicated enzymatic network surrounding fatty acid biosynthesis.</p

Deep-Learning-Enabled Fast Optical Identification and Characterization of Two-Dimensional Materials

Advanced microscopy and/or spectroscopy tools play indispensable role in nanoscience and nanotechnology research, as it provides rich information about the growth mechanism, chemical compositions, crystallography, and other important physical and chemical properties. However, the interpretation of imaging data heavily relies on the "intuition" of experienced researchers. As a result, many of the deep graphical features obtained through these tools are often unused because of difficulties in processing the data and finding the correlations. Such challenges can be well addressed by deep learning. In this work, we use the optical characterization of two-dimensional (2D) materials as a case study, and demonstrate a neural-network-based algorithm for the material and thickness identification of exfoliated 2D materials with high prediction accuracy and real-time processing capability. Further analysis shows that the trained network can extract deep graphical features such as contrast, color, edges, shapes, segment sizes and their distributions, based on which we develop an ensemble approach topredict the most relevant physical properties of 2D materials. Finally, a transfer learning technique is applied to adapt the pretrained network to other applications such as identifying layer numbers of a new 2D material, or materials produced by a different synthetic approach. Our artificial-intelligence-based material characterization approach is a powerful tool that would speed up the preparation, initial characterization of 2D materials and other nanomaterials and potentially accelerate new material discoveries

Harnessing biodiesel-producing microbes : from genetic engineering of lipase to metabolic engineering of fatty acid biosynthetic pathway

Microbial production routes, notably whole-cell lipase-mediated biotransformation and fatty-acids-derived biosynthesis, offer new opportunities for synthesizing biodiesel. They compare favorably to immobilized lipase and chemically catalyzed processes. Genetically modified whole-cell lipase-mediated in vitro route, together with in vivo and ex vivo microbial biosynthesis routes, constitutes emerging and rapidly developing research areas for effective production of biodiesel. This review presents recent advances in customizing microorganisms for producing biodiesel, via genetic engineering of lipases and metabolic engineering (including system regulation) of fatty-acids-derived pathways. Microbial hosts used include Escherichia coli, Saccharomyces cerevisiae, Pichia pastoris and Aspergillus oryzae. These microbial cells can be genetically modified to produce lipases under different forms: intracellularly expressed, secreted or surface-displayed. They can be metabolically redesigned and systematically regulated to obtain balanced biodiesel-producing cells, as highlighted in this study. Such genetically or metabolically modified microbial cells can support not only in vitro biotransformation of various common oil feedstocks to biodiesel, but also de novo biosynthesis of biodiesel from glucose, glycerol or even cellulosic biomass. We believe that the genetically tractable oleaginous yeast Yarrowia lipolytica could be developed to an effective biodiesel-producing microbial cell factory. For this purpose, we propose several engineered pathways, based on lipase and wax ester synthase, in this promising oleaginous host

Harnessing biodiesel-producing microbes: from genetic engineering of lipase to metabolic engineering of fatty acid biosynthetic pathway

Microbial production routes, notably whole-cell lipase-mediated biotransformation and fatty-acids-derived biosynthesis, offer new opportunities for synthesizing biodiesel. They compare favorably to immobilized lipase and chemically catalyzed processes. Genetically modified whole-cell lipase-mediated in vitro route, together with in vivo and ex vivo microbial biosynthesis routes, constitutes emerging and rapidly developing research areas for effective production of biodiesel. This review presents recent advances in customizing microorganisms for producing biodiesel, via genetic engineering of lipases and metabolic engineering (including system regulation) of fatty-acids-derived pathways. Microbial hosts used include Escherichia coli, Saccharomyces cerevisiae, Pichia pastoris and Aspergillus oryzae. These microbial cells can be genetically modified to produce lipases under different forms: intracellularly expressed, secreted or surface-displayed. They can be metabolically redesigned and systematically regulated to obtain balanced biodiesel-producing cells, as highlighted in this study. Such genetically or metabolically modified microbial cells can support not only in vitro biotransformation of various common oil feedstocks to biodiesel, but also de novo biosynthesis of biodiesel from glucose, glycerol or even cellulosic biomass. We believe that the genetically tractable oleaginous yeast Yarrowia lipolytica could be developed to an effective biodiesel-producing microbial cell factory. For this purpose, we propose several engineered pathways, based on lipase and wax ester synthase, in this promising oleaginous host

Natural Products from Actinomycetes Associated with Marine Organisms

The actinomycetes have proven to be a rich source of bioactive secondary metabolites and play a critical role in the development of pharmaceutical researches. With interactions of host organisms and having special ecological status, the actinomycetes associated with marine animals, marine plants, macroalgae, cyanobacteria, and lichens have more potential to produce active metabolites acting as chemical defenses to protect the host from predators as well as microbial infection. This review focuses on 536 secondary metabolites (SMs) from actinomycetes associated with these marine organisms covering the literature to mid-2021, which will highlight the taxonomic diversity of actinomycetes and the structural classes, biological activities of SMs. Among all the actinomycetes listed, members of Streptomyces (68%), Micromonospora (6%), and Nocardiopsis (3%) are dominant producers of secondary metabolites. Additionally, alkaloids (37%), polyketides (33%), and peptides (15%) comprise the largest proportion of natural products with mostly antimicrobial activity and cytotoxicity. Furthermore, the data analysis and clinical information of SMs have been summarized in this article, suggesting that some of these actinomycetes with multiple host organisms deserve more attention to their special ecological status and genetic factors

Cascade alkylarylation of substituted N-allylbenzamides for the construction of dihydroisoquinolin-1(2H)-ones and isoquinoline-1,3(2H,4H)-diones Full Research Paper Open Access

Abstract An oxidative reaction for the synthesis of 4-alkyl-substituted dihydroisoquinolin-1(2H)-ones with N-allylbenzamide derivatives as starting materials has been developed. The radical alkylarylation reaction proceeds through a sequence of alkylation and intramolecular cyclization. The substituent on the C-C double bond was found to play a key role for the progress of the reaction to give the expected products with good chemical yields. Additionally, N-methacryloylbenzamides were also suitable substrates for the current reaction and provided the alkyl-substituted isoquinoline-1,3(2H,4H)-diones in good yield. 30

Dynamic dual-crosslinking antibacterial hydrogel with enhanced bio-adhesion and self-healing activities for rapid hemostasis in vitro and in vivo

Bio-adhesives based on natural polymer silk fibroin (SF) are high-profiled in the development of rapid hemostatic agents because of their good biocompatibility and biodegradability. However, the lack of bioactivity, mechanical and bio-adhesion performance, restrict their use in the biomedical field. Herein, based on the dynamic dual-crosslinking mechanism, we fabricated a silk microfibers (SMFs)-based multifunctional hemostatic hydrogel by incorporating tannic acid-coated SMF (TA@SMF) motifs into the network of poly(vinyl alcohol)-borax (PB) hydrogel. The cohesion-enhancing strategy, along with dynamic borate-diol bonds and hydrogen bonds, synergically provide the hydrogel with enhanced bio-adhesion and self-healing properties. TA@SMF/PB gel has an elongation at break of more than 600% and adheres to pig skin even after 24 h immersion in water. In vitro experiments have shown good antibacterial, antioxidant, biocompatibility, and hemostatic properties of the TA@SMF/PB gel. In vivo degradation and mouse liver hemostatic test further verified its biosafety and rapid hemostasis performance. The hemostatic time of 42.0 ± 4.9 s in [email protected] was significantly shorter than that in other experimental groups. This study is the original report for functionalizing SMFs with TA as a hemostasis material, which affords a versatile SMF-based toolkit that provides promising candidate materials for rapid hemostatic and infectious wound healing