Modulating the catalytic activity of enzyme-like nanoparticles through their surface functionalization

The inclusion of transition metal catalysts into nanoparticle scaffolds permits the creation of catalytic nanosystems (nanozymes) able to imitate the behaviour of natural enzymes. Here we report the fabrication of a family of nanozymes comprised of bioorthogonal ruthenium catalysts inserted in the protective monolayer of gold nanoparticles. By introducing simple modifications to the functional groups at the surface of the nanozymes, we have demonstrated control over the kinetic mechanism of our system. Cationic nanozymes with hydrophobic surface functionalities tend to replicate the classical Michaelis Menten model, while those with polar groups display substrate inhibition behaviour, a key mechanism present in 20% of natural enzymes. The structural parameters described herein can be used for creating artificial nanosystems that mimic the complexity observed in cell machinery. © 2018 The Royal Society of Chemistry

Protein-mediated dethreading of a biotin-functionalised pseudorotaxane

In this article, we describe the synthesis of new biotin-functionalised naphthalene derivatives 3 and 4 and their complexation behaviour with avidin and neutravidin using a range of analytical techniques. We have shown using 2-(4prime or minute-hydroxyazobenzene)benzoic acid displacement and ITC experiments{,} that compounds 3 and 4 have the propensity to form reasonably high-affinity bioconjugates with avidin and neutravidin. We have also demonstrated using 1H NMR{,} UV-vis and fluorescence spectroscopy that the naphthalene moiety of 3 and 4 facilitates the formation of pseudorotaxane-like structures with 1 in water. We have then investigated the ability of avidin and neutravidin to modulate the complexation between 1 and 3 or 4. UV-vis and fluorescence spectroscopy has shown that in both cases the addition of the protein disrupts complexation between the naphthalene moieties of 3 and 4 with 1

Flavin-functionalized amphiphilic block copolymer gela

The synthesis of flavin-containing amphiphilic block copolymers using atom transfer radical polymerisation (ATRP) is described. In these systems, a flavin moiety is engineered into the ATRP initiator unit as an environmental probe and is subsequently used to produce three block copolymers featuring a hydrophobic methacrylate block and a DMAEM block. The dimethylamino unit of the latter is converted to a trimethylammonium unit to afford three amphiphilic block copolymers. Rheological measurements show that these materials form gels in dilute aqueous solution that can be disrupted upon irradiation with ultrasound. The disruption of the gel can be conveniently monitored by exploiting the solvatochromic nature of the S0–S2 absorption in the UV-vis spectrum in response to its changing environment

An investigation of the complexation behaviour of structurally modified tetrathiafulvalene derivatives with the electron deficient cyclophane cyclobis(paraquat-p-phenylene)

This study has shown that easily oxidisable TTF units form charge-transfer (C-T) complexes with 7 which have the largest reported association constants to date. Replacing the sulfur of the TTF unit with selenium or extending the conjugated link between the two dithiole rings reduces the K-a of the complex relative to the parent derivative. (C) 2001 Published by Elsevier Science Ltd

Solution-processed boron subphthalocyanine derivatives as acceptors for organic bulk-heterojunction solar cells

GC and IDWS thank the EPSRC for funding (Grant EP/I00243X). NBAP thanks Directorate General of Higher Education (DGHE) of Republic Indonesia for PhD Scholarship Grant (948/E4.4/K/2013). IDWS also acknowledges a Royal Society Wolfson Research Merit Award.We report the fabrication of solution-processed bulk heterojunction devices from subphthalocyanine (SubPc) units as the acceptor component and conventional polymeric donor materials such as MEH-PPV, P3HT and PTB7. The high solubility of the SubPc derivatives facilitated the formation of efficient donor/acceptor networks and provided power conversion efficiencies of 0.4% with MEH-PPV, 1.1% with P3HT and 3.5% with PTB7. A clear contribution of photon harvesting by the acceptor was identified from the external quantum efficiency spectra. Analysis of the current-voltage characteristics and photoluminescence quenching revealed trap-assisted and geminate recombination as a loss mechanism. Our results show that solution-processable SubPcs are a promising alternative to fullerenes for polymer solar cells.Publisher PDFPeer reviewe

A stopperless tetrathiafulvalene based 2 pseudorotaxane molecular shuttle

The first stopperless TTF containing molecular shuttle is described. (C) 2001 Elsevier Science Ltd. All rights reserved