Novel applications of surface-modified sporopollenin exine capsules

The external shell (exine) of plant spores and pollen grains is composed of sporopollenin, which is an organic polymer renowned for its exceptional resistance to physical and chemical attack. The resilience of sporopollenin to high temperature, pressures, acidic and basic corrosion is proved by its survival in some sedimentary rocks, which are 500 million years old.Solid phase organic synthesis is a process where molecules or reagents are used whilst attached to an insoluble and filterable solid support. Sporopollenin could have a series of advantages over commercial resins if it can be applied to solid phase synthesis as it has a constant chemical structure, constant pore size, and in particular chemical and physical stability.In this study sporopollenin was first extracted from fresh pollen and spores, and then modified to make a basic form by attachment of alkyldiamines, and an acidic form by treatment with chlorosulfonic or sulfuric acid. Detailed studies were undertaken regarding the use of the base form of sporopollenin in Schotten-Baumann type acylations and Knoevenagel condensations, and the acidic form of sporopollenin in the isopropylidene protection of mannose and preparation of cyclic acetal. As a result, aminated sporopollenin particles were shown to be effective scavengers in Schotten-Baumann acylation and they catalyse Knoevenagel condensation successfully.The sulfonated sporopollenin particles also reveal their ability in catalysing relative reactions.Raw spores and simply extracted sporopollenin has been investigated for the stabilization of Pickering emulsion by Binks et al. In this work, sporopollenin was aminated and their behaviour as emulsifiers has been studied. The amino groups on the surface of sporopollenin will change the hydrophilicity of the particles and affect their behaviour in the emulsions

Sulfonated sporopollenin as an efficient and recyclable heterogeneous catalyst for dehydration of D-xylose and xylan into furfural

The natural acidity of sporopollenin, the biopolymer coating the outer walls of pollen grains, was enhanced by the sulfonation of its surface. Modified sporopollenin displaying sulfonic acid groups has been prepared, characterized by elemental analysis, SEM, EDX, FTIR and XPS and tested as a heterogeneous catalyst in the dehydration of D-xylose and xylan to produce furfural. The optimal reaction conditions involve 10 wt % of sulfonated sporopollenin in the presence of 1.5 mmol of NaCl in a biphasic water-CPME system. When heated at 190 °C, the reaction affords furfural in a yield of 69% after 40 min under microwave irradiation. The time dependence of the dehydration and influence of temperature, pentose loading and positive effect of chloride ions on the reaction rate are reported. It was found that the catalytic system, recharged with the pentose and solvent, could be recycled ten times without loss of performance. The transformation of xylan into furfural at 190 °C for 50 min gave furfural in a yield of 37%

Sporopollenin as an efficient green support for covalent immobilization of a lipase

Sporopollenin exine capsules (SECs), derived from the spores of Lycopodium clavatum, have been functionalised with 1,n-diamines and the resulting aminoalkyl microcapsules used to immobilize Candida antarctica lipase B (Cal B) via a glutaradehyde-based diimine covalent linker. The supported enzyme efficiently catalyzes the esterification of oleic acid with ethanol. Initial rates using the SEC-CalBs were comparable to the commercial enzyme Novozym 435, but displayed up to 20-fold higher specific activity. The supported enzymes could also be recycled and after four cycles displayed only a modest decrease in conversions. In a kinetic resolution the SEC-CalBs efficiently acetylated rac-1-phenylethanol, with conversions up to 37% after 5 hours and product enantiomeric excesses of >99%. Related to this, the dynamic resolution of rac-1-phenylethylamine, in the presence of Pd-BaSO₄ and ammonium formate, led to the acetylated amine with a 94% conversion and >99% ee

Sequestration of edible oil from emulsions using new single and double layered microcapsules from plant spores

International audienc

CRISPR-dCas13-tracing reveals transcriptional memory and limited mRNA export in developing zebrafish embryos

Abstract Background Understanding gene transcription and mRNA-protein (mRNP) dynamics in single cells in a multicellular organism has been challenging. The catalytically dead CRISPR-Cas13 (dCas13) system has been used to visualize RNAs in live cells without genetic manipulation. We optimize this system to track developmentally expressed mRNAs in zebrafish embryos and to understand features of endogenous transcription kinetics and mRNP export. Results We report that zygotic microinjection of purified CRISPR-dCas13-fluorescent proteins and modified guide RNAs allows single- and dual-color tracking of developmentally expressed mRNAs in zebrafish embryos from zygotic genome activation (ZGA) until early segmentation period without genetic manipulation. Using this approach, we uncover non-synchronized de novo transcription between inter-alleles, synchronized post-mitotic re-activation in pairs of alleles, and transcriptional memory as an extrinsic noise that potentially contributes to synchronized post-mitotic re-activation. We also reveal rapid dCas13-engaged mRNP movement in the nucleus with a corralled and diffusive motion, but a wide varying range of rate-limiting mRNP export, which can be shortened by Alyref and Nxf1 overexpression. Conclusions This optimized dCas13-based toolkit enables robust spatial-temporal tracking of endogenous mRNAs and uncovers features of transcription and mRNP motion, providing a powerful toolkit for endogenous RNA visualization in a multicellular developmental organism

Sequestration of edible oil from emulsions using new single and double layered microcapsules from plant spores

Microcapsules were obtained conveniently from Lycopodium clavatum spores possessing either a single layered shell of sporopollenin (exine) or double layered shell of sporopollenin and cellulose with an inner layer (intine). These microcapsules were further modified by converting their surface hydroxyl groups (alcohols, phenols carboxylic acids) into salts (Na+and K+), acetates and methyl ethers accordingly. All of these new types of microcapsules were found to sequester efficiently edible oils from oil-in-water emulsions with the acetylated forms being the most efficient to sequester oils in near quantitative fashion. The latter could be recycled without losing efficiency to recover oil. Oils could also be released from the microcapsules in a stepwise manner by repeated rubbing