Genome Characterization of the Oleaginous Fungus Mortierella alpina

Mortierella alpina is an oleaginous fungus which can produce lipids accounting for up to 50% of its dry weight in the form of triacylglycerols. It is used commercially for the production of arachidonic acid. Using a combination of high throughput sequencing and lipid profiling, we have assembled the M. alpina genome, mapped its lipogenesis pathway and determined its major lipid species. The 38.38 Mb M. alpina genome shows a high degree of gene duplications. Approximately 50% of its 12,796 gene models, and 60% of genes in the predicted lipogenesis pathway, belong to multigene families. Notably, M. alpina has 18 lipase genes, of which 11 contain the class 2 lipase domain and may share a similar function. M. alpina's fatty acid synthase is a single polypeptide containing all of the catalytic domains required for fatty acid synthesis from acetyl-CoA and malonyl-CoA, whereas in many fungi this enzyme is comprised of two polypeptides. Major lipids were profiled to confirm the products predicted in the lipogenesis pathway. M. alpina produces a complex mixture of glycerolipids, glycerophospholipids and sphingolipids. In contrast, only two major sterol lipids, desmosterol and 24(28)-methylene-cholesterol, were detected. Phylogenetic analysis based on genes involved in lipid metabolism suggests that oleaginous fungi may have acquired their lipogenic capacity during evolution after the divergence of Ascomycota, Basidiomycota, Chytridiomycota and Mucoromycota. Our study provides the first draft genome and comprehensive lipid profile for M. alpina, and lays the foundation for possible genetic engineering of M. alpina to produce higher levels and diverse contents of dietary lipids

Preparation of a Rapidly Forming Poly(ferrocenylsilane)-Poly(ethylene glycol)-based Hydrogel by a Thiol-Michael Addition Click Reaction

The synthesis of a rapidly forming redox responsive poly(ferrocenylsilane)-poly(ethylene glycol) (PFS-PEG)-based hydrogel is described, achieved by a thiol-Michael addition click reaction. PFS bearing acrylate side groups (PFS-acryl) was synthesized by side group modification of poly(ferrocenyl(3-iodopropyl)methylsilane) (PFS-I) and characterized by 1H NMR, 13C NMR, and FT-IR spectroscopy. The equilibrium swelling ratio, morphology, rheology, and redox responsive properties of the PFS-PEG-based hydrogel are reported

Redox-controlled release of molecular payloads from multilayered organometallic polyelectrolyte films

Organometallic poly(ferrocenylsilane)s (PFSs) featuring redox responsive ferrocene units in their main chain are prepared and characterized for redox triggered film disassembly and release of molecular payloads. Positively or negatively charged side groups render PFS water soluble and these polyelectrolytes also allow the use of an electrostatic self-assembly process for the fabrication of novel functional supermolecular nanostructures. The layer-by-layer (LbL) electrostatic fabrication approach is utilized to obtain films with different bilayer numbers. The electrochemical behaviour of the multilayers with different thicknesses is recorded by capturing cyclic voltammograms (CVs). Film disassembly (multilayer re-dispersed in water) is performed by exposing the multilayers to the different values of holding potentials, corresponding to partial or full oxidation of PFS. Disassembly kinetics is quantitatively monitored by determining the amount of polymer released from CV experiments, as well as from UV-VIS spectroscopy. The proposed PFS multilayer disassembly mechanism is presented. The morphology of the multilayer films as a function of holding times is monitored by AFM. The release of guest molecules such as fluorescent Alexa dyes incorporated at different depths in the multilayer films is studied by fluorescence spectroscop

Grafting of Single, Stimuli-Responsive Poly(ferrocenylsilane) Polymer Chains to Gold Surfaces

Redox-responsive poly(ferrocenylsilane) (PFS) polymer molecules were attached individually to gold surfaces for force spectroscopy experiments on the single molecule level. By grafting ethylenesulfide-functionalized PFS into the defects of preformed self-assembled monolayers (SAMs) of different -mercaptoalkanols on Au(111), the surface coverage of PFS macromolecules could be conveniently controlled. Atomic force microscopy (AFM), contact angle, as well as cyclic and differential pulse voltammetry measurements were carried out to characterize the morphology, wettability, and surface coverage of the grafted layers. The values of the PFS surface coverage were found to depend on the chain length of the -mercaptoalkanol molecules and on the concentration of the PFS solution but not on the insertion time or on the molar mass of PFS. The equilibrium surface coverages were successfully described by Langmuir adsorption isotherms. For low-surface coverage values (<6.2 × 10-4 chain/nm2), achieved by PFS insertion from very dilute solutions (8 × 10-6 M) into long-chain SAMs, AFM and differential pulse voltammetry showed that surfaces exposing isolated individual polymer chains were obtained. The isolated PFS macromolecules were subjected to in situ AFM-based single molecule force spectroscopy (SMFS) measurements. The single chain elasticity of PFS in isopropanol (and ethanol) was fitted with the modified freely jointed chain (m-FJC) model. This procedure yielded a Kuhn segment length of 0.33 ± 0.05 nm and a segment elasticity of 32 ± 5 nN/n