The biofilm matrix scaffold of Pseudomonas aeruginosa contains G-quadruplex extracellular DNA structures

Extracellular DNA, or eDNA, is recognised as a critical biofilm component; however, it is not understood how it forms networked matrix structures. Here, we isolate eDNA from static-culture Pseudomonas aeruginosa biofilms using ionic liquids to preserve its biophysical signatures of fluid viscoelasticity and the temperature dependency of DNA transitions. We describe a loss of eDNA network structure as resulting from a change in nucleic acid conformation, and propose that its ability to form viscoelastic structures is key to its role in building biofilm matrices. Solid-state analysis of isolated eDNA, as a proxy for eDNA structure in biofilms, reveals non-canonical Hoogsteen base pairs, triads or tetrads involving thymine or uracil, and guanine, suggesting that the eDNA forms G-quadruplex structures. These are less abundant in chromosomal DNA and disappear when eDNA undergoes conformation transition. We verify the occurrence of G-quadruplex structures in the extracellular matrix of intact static and flow-cell biofilms of P. aeruginosa, as displayed by the matrix to G-quadruplex-specific antibody binding, and validate the loss of G-quadruplex structures in vivo to occur coincident with the disappearance of eDNA fibres. Given their stability, understanding how extracellular G-quadruplex structures form will elucidate how P. aeruginosa eDNA builds viscoelastic networks, which are a foundational biofilm property.

Fabrication of Soft-Oxometalates {Mo132} Clusters With Novel Azobenzene Surfactants: Size Control by Micelles and Light

Soft-oxometalates (SOMs) are colloid suspensions of superstructured assemblies of polyoxometalates (POMs) and are found to be very effective photo-catalysts in a number of chemical reactions. The stabilization of SOMs generally requires legends or stabilizers, e.g., polymers and surfactants. In this paper, a light responsive azobenzene surfactant, C10AZOC2N3, was developed and used to stable {Mo132} SOMs. Various techniques such as Dynamic light scattering, TEM, UV-Vis spectra and cyclic voltammetry were employed to characterize the experimental results. The outstanding structure-directing effect of surfactant self-assembly micelles in solution on inorganic counter-anions was demonstrated. Different amount of cyclohexane was solubilized into C10AZOC2N3 micelles to successfully control the size of {Mo132} SOMs cluster. Furthermore, the clusters exposed to UV light for a certain time can be served as a second trigger to control the size of SOMs due to the trans-cis conformation transition of surfactant molecules. The redox potentials of C10AZOC2N3-{Mo132} SOMs were investigated as the cluster size varied. Interestingly, the redox potential of {Mo132} was not affected by the cluster size, indicating that the presence of surfactant did not change the main function of {Mo132} as an electrochemical catalyst, but merely assisted in the size control of SOM aggregation.

Moderate conformational transition promotes the formation of a self-reinforced highly oriented silk fibroin network structure

Moderate conformation transition promotes the formation of low-density crosslinking molecular network and further rearrangement of amorphous proteins to form the highly oriented molecular network structure, which paved the way for achieving mechanical-enhanced silk fibroin materials.

Gas-Phase Synthesis and Deposition of Metal-bipyridine Complex [M-bpy1-2]+ (M=Ag, Cu) with Conformation Transition

Controllable synthesis of organometallic clusters in gas phase is a topic of reasonable interest with precisely tunable properties depending on size, composition, and intra-cluster charge-transfer interactions. Here we have prepared...

Effect of Thermal Annealing on Conformation of MEH-PPV Chains in Polymer Matrix: Coexistence of H- and J-Aggregates

In diluted solid solution using poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) and polymethyl methacrylate (PMMA) or polystyrene (PS), both aggregated and extended conformations could be formed according to the weight ratio. Aggregated conformation in as-cast MEH-PPV/PMMA film presented a J-aggregate-like photoluminescence (PL) emission. After annealing at 160 °C, its PL showed characteristics of both J- and H-aggregates at the same time; however, extended conformation showed an oligomer-like emission, which was not sensitive to either measurement temperature or annealing temperature. Thus, the conformation transition between aggregated and extended is unlikely to happen in MEH-PPV/PMMA blends during thermal annealing. On the contrary, in MEH-PPV/PS blends, extended conformation dominated in as-cast film with oligomer-like emissions; after annealing at 160 °C, both J- and H- aggregate-like PL emissions were observed, indicating the conformation transitioned from extended to aggregated. Therefore, our work may suggest a new method to manipulate photophysical properties of conjugated polymers by combining appropriate host matrix and thermal annealing processes.

Laser-Driven Aggregation in Dextran–Graft–PNIPAM/Silver Nanoparticles Hybrid Nanosystem: Plasmonic Effects

The laser-induced aggregation in the thermosensitive dextran grafted-poly(N-isopropylacrylamide) copolymer/Ag nanoparticles (D–g–PNIPAM/AgNPs) hybrid nanosystem in water has been observed. The laser-induced plasmonic heating of Ag NPs causes the Lower Critical Solution Temperature (LCST) conformation transition in D–g–PNIPAM/AgNPs macromolecules which shrink during the transition. The shrinking decreases sharply the distance between the silver nanoparticles that launches the aggregation of Ag NPs and the appearance of plasmonic attractive optical forces acting between the nanoparticles. It has been shown that the approach of the laser wavelength to the surface plasmon resonance in Ag nanoparticles leads to a significant strengthening of the observed aggregation, which proves its plasmon nature. The laser-induced transformations in the D–g–PNIPAM/AgNPs nanosystem have been found to be essentially irreversible that differs principally them from the temperature-induced transformations. Such fundamental difference proves the crucial role of the optical forces arising due to the excitation of surface plasmons in Ag NPs.

Chain conformation transition induced host–guest assembly between triple helical curdlan and β-CD for drug delivery

A novel kind of supramolecular micelle consisting of the triplex curdlan and β-CDs was firstly developed via the conformation transition induced host–guest interaction.