Subcellular optogenetic inhibition of G proteins generates signaling gradients and cell migration

Cells sense gradients of extracellular cues and generate polarized responses such as cell migration and neurite initiation. There is static information on the intracellular signaling molecules involved in these responses, but how they dynamically orchestrate polarized cell behaviors is not well understood. A limitation has been the lack of methods to exert spatial and temporal control over specific signaling molecules inside a living cell. Here we introduce optogenetic tools that act downstream of native G protein–coupled receptor (GPCRs) and provide direct control over the activity of endogenous heterotrimeric G protein subunits. Light-triggered recruitment of a truncated regulator of G protein signaling (RGS) protein or a Gβγ-sequestering domain to a selected region on the plasma membrane results in localized inhibition of G protein signaling. In immune cells exposed to spatially uniform chemoattractants, these optogenetic tools allow us to create reversible gradients of signaling activity. Migratory responses generated by this approach show that a gradient of active G protein αi and βγ subunits is sufficient to generate directed cell migration. They also provide the most direct evidence so for a global inhibition pathway triggered by Gi signaling in directional sensing and adaptation. These optogenetic tools can be applied to interrogate the mechanistic basis of other GPCR-modulated cellular functions

Pickering emulsifiers based on hydrophobically modified small granular starches Part II – Effects of modification on emulsifying capacity

Small granular starches from rice, quinoa, and amaranth were modified with octenyl succinic anhydride (OSA) at 5 defined intervals (0–3.0%) and investigated with respect to emulsifying capacity and stability. Starch granule surfaces were characterized by Brunauer–Emmett–Teller and contact angle measurements. Emulsifying capacity was characterized by multiple light scattering (MLS) and particle size analysis. Stability towards environmental stress was characterized by centrifugation and MLS. Surface hydrophobicity and emulsifying capacity correlated with starch type and modification level. Quinoa stabilized emulsions had the smallest droplet size (e.g. 59.2 μm at 3.0% OSA) and superior stability, both before and after centrifugation, especially at the lowest modification levels. Rice and amaranth had larger droplets (99.8 and 84.1 μm at 3.0% OSA respectively). Amaranth, despite its small size showed poorer performance than quinoa, especially at lower modification levels. The higher emulsifying efficiency of quinoa starch granules attributed to the higher protein content

Characterization and stability of short-chain fatty acids modified starch Pickering emulsions

Acetylated, propionylated and butyrylated rice and quinoa starches at different levels of modification and starch concentrations, were used to stabilize oil-in-water starch Pickering emulsions at 10% oil fraction. Short-chain fatty acid modified starch Pickering emulsions (SPEs) were characterized after emulsification and after 50 days of storage. The particle size distribution, microstructure, emulsion index, and stability were evaluated. An increase in starch concentration led to a decrease of emulsion droplet sizes. Quinoa starch has shown the capability of stabilizing Pickering emulsions in both the native and modified forms. The emulsifying capacity of SPEs was improved by increasing the chain length of SCFA. Modified quinoa starch with higher chain lengths (i.e. propionylated and butyrylated), at higher levels of modification, showed higher emulsion index (>71%) and stability over the entire 50 days storage. At optimized formulation, SCFA-starch particles have the potential in stabilizing emulsions for functional foods, pharmaceutical formulations, or industrial food applications

Pickering emulsifiers based on hydrophobically modified small granular starches – Part I : Manufacturing and physico-chemical characterization

Small granular starches from rice, quinoa and amaranth were hydrophobized by esterification with octenyl succinic anhydride (OSA) in an aqueous alkaline slurry to obtain series of modified starches at defined intervals (i.e. 0.6, 1.2, 1.8, 2.4, 3.0%). The physical and the physico-chemical properties of the starch particles were characterized by proximate analysis including protein level, amylose level and dry matter. The shape and size of the starch granules were characterized by scanning electron microscopy and light scattering. The gelatinization properties were characterized by differential scanning calorimetry. The degree of modification was determined by titration with NaOH. With regard to the emulsion formulation and in order to assess the emulsifying capacity of the small granular starches, the effect of starch type, degree of modification and starch concentration on the resulting emulsion droplet size were evaluated by light scattering and optical microscopy. Emulsifying properties were found to depend on the degree of substitution, size of the granules and the starch to oil ratio of the formulation. Quinoa starch granules, in general, had the best emulsifying capacity followed by amaranth and rice. However, in higher starch concentrations (>400 mg/mL oil) and adequate levels of OSA (3.0%) amaranth performed best, having the smallest size of starches studied

Semitechnical methods for the isolation of arabinoxylans from wheat bran

Wheat bran is an important by-product of the wheat milling industry and accounts for 11 to 19% of the grain. For rye and barley it amounts to around 22 %. It mainly consists of dietary fiber (43-53%). The fiber fraction includes arabinoxylans (AX) (38-55%), cellulose (16-30%), lignin (5-20%) and other nonstarch polysaccharides. Dietary fibers are generally associated with a reduction of the risk of civilization diseases. AX included in the fibers are prized for their potential to prevent colon cancer. Health benefits don´t depend only on the content of AX, but also on their physical properties such as solubility, viscosity, branching and molecular weight. Physical properties, e.g. the molecular weight of AX is influenced by cultivation conditions and cereal processing technologies. Arabinoxylans are readily fermented by the colonic microflora to short chain fatty acids (SCFA - acetate, propionate, butyrate). SCFA serve as an energy source for intestinal epithelial cells and reduce the pH in the intestine, thereby preventing the overgrowth of pathogenic bacteria. An important part of the AX is ferulic acid, which has antioxidant properties. The aim of this study was to optimize the parameters of the individual isolation steps for an economic production of AX from wheat bran. The experiments were carried out in a laboratory and semitechnical scale up to 10 kg of wheat bran in one batch. The content of AX was 24.5 % in dry matter (d.m.). First of all starch and cold water-soluble compounds were separated by aqueous suspension and wet sieving. The subsequent extraction was performed either with hydrogen peroxide in a alkaline medium or with water under elevated pressure in a stirred autoclave. From the aqueous slurry of the bran the solids were removed by centrifugation using laboratory centrifuges. For preconcentration of AX and separation of low molecular weight compounds ultra- and diafiltration were choosen, using polysulfone membranes with a molar cut off of 10,000 g/mol. AX was subsequently precipitated from the solution by addition of 96% ethanol with a mass ratio of 3.2 to 1. To increase the shelf-life of the final products they were freeze or spray dried. High purity AX (69.8% in d.m.) was achieved by using hydrogen peroxide in an alkaline medium. In this case the molar mass Mw was 70,200 g/mol. The isolated AX is excellent soluble in cold water and can be used such as a thickening agent in the food industry or for technical purposes. By using water in a temperature range of 147-163°C as an extraction medium, the purity of the final products was considerable lower (47.3-58.6% AX in d.m.) The molar mass of these AX-products was significantly affected by the extraction conditions and ranged from 11,100-220,000 g/mol. The cold water solubility was poor

Entwicklung biologisch abbaubarer Werkstoffe auf der Basis nachwachsender Rohstoffe, Staerke, Pflanzenoel und Naturfasern. Teilprojekt 1: Derivatisierung der Fette Abschlussbericht

Based on starch and vegetable oils a new class of engineering plastics has been developed, that exhibit enhanced property profiles in comparison with thermoplastic starches, especially enhanced humidity resistance. Via reacting starch with hydrophobic compounds like vegetable oils, starch derivatives with taylor-made hydrophobicity, mechanical strength and biodegradation could be obtained. Environmentally friendly derivatization methods were performed in aqueous media. Etherification of starch was carried out with alkyl halogenides and epoxides, and hydroxyalkylation was performed with alpha-epoxides, glycidyl ethers and styrene oxide. Esterification was carried out via imidazoline route, and the base-catalyzed reactions with cyclic anhydrides, i.e., phthalic anhydride and 1,2-epoxy butane, and by reaction of maize amylo-starch with vinyl laurate.The starch derivatives were characterized by NMR, GPC, FTIR, and elemental analyses.Available from TIB Hannover: F03B678 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung und Forschung, Berlin (Germany); Bundesministerium fuer Verbraucherschutz, Ernaehrung und Landwirtschaft (BMVEL), Berlin (Germany)DEGerman

Chemische Nutzung heimischer Pflanzenoele II. Teilprojekt 5: Tenside, Kunststoff-Bausteine und Polymere aus heimischen Pflanzenoelen durch Metall- und Biokatalyse Abschlussbericht

Native plant oils have been used as sustainable resources for plastics production. This research project describes the following results: Structured sugar tensides based on sugar amines like N-methylglucamin, galactamines, and disaccharide amines; hydroxy fatty acid esters for the production of polyesters, polyurethanes, and tensides; Preparation of fatty epoxides via chemo-enzymatic epoxidation of unsaturated fats substances; Unusual dicarboxy acids for novel polyesters; Production of polymers with native plant oils via polymerisation and polycondensation reactions.SIGLEAvailable from TIB Hannover: F03B449 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung und Forschung, Berlin (Germany); Bundesministerium fuer Ernaehrung, Landwirtschaft und Forsten, Berlin (Germany)DEGerman