Green synthesis and antioxidant activity of new PEGylated ferulic acids

PEGylation of ferulic acid is described through a green esterification process involving poly(ethylene glycol) (PEG) with three different average molecular weights (200, 400 and 1000 g/mol) as both reactive and solvent. Esterification with PEG400 and PEG1000 leads to original compounds soluble in all proportions in water. These new compounds display an antioxidant activity similar to that of ferulic acid.     

Elongated thrombin binding aptamer: a G-quadruplex cation-sensitive conformational switch

Aptamer-based biosensors offer promising perspectives for high performance, specific detection of proteins. The thrombin binding aptamer (TBA) is a G-quadruplex-forming DNA sequence, which is frequently elongated at one end to increase its analytical performances in a biosensor configuration. Herein, we investigate how the elongation of TBA at its 5'?end affects its structure and stability. Circular dichroism spectroscopy shows that TBA folds in an antiparallel G-quadruplex conformation with all studied cations (Ba(2+), Ca(2+), K(+), Mg(2+), Na(+), NH(4)(+), Sr(2+) and the [Ru(NH(3))(6)](2+/3+) redox marker) whereas other structures are adopted by the elongated aptamers in the presence of some of these cations. The stability of each structure is evaluated on the basis of UV spectroscopy melting curves. Thermal difference spectra confirm the quadruplex character of all conformations. The elongated sequences can adopt a parallel or an antiparallel structure, depending on the nature of the cation; this can potentially confer an ion-sensitive switch behavior. This switch property is demonstrated with the frequently employed redox complex [Ru(NH(3))(6)](3+), which induces the parallel conformation at very low concentrations (10 equiv per strand). The addition of large amounts of K(+) reverts the conformation to the antiparallel form, and opens interesting perspectives for electrochemical biosensing or redox-active responsive devices.     

A Flexible Terpyridine Derivative Interacts Specifically with G‐Quadruplexes

G‐quadruplexes formed by nucleic acids are implicated in pathologies ranging from cancers to neurodegenerative diseases. We evaluated interactions of 29 bi‐ and terpyridine derivatives with G‐quadruplexes and duplexes. FRET‐melting, circular dichroism, and ¹H NMR spectroscopy showed that one terpyridine derivative interacted very selectively with G‐quadruplexes. This G‐quadruplex ligand inhibited helicase activity and should influence G‐quadruplex‐related biological processes.     

Impact of formic/acetic acid and ammonia pre-treatments on chemical structure and physico-chemical properties of Miscanthus x giganteus lignins

Miscanthus x giganteus was treated with formic acid/acetic acid/water (30/50/20 v/v) for 3 h at 107 °C and 80 °C, and soaking in aqueous ammonia (25% w/w) for 6 h at 60 °C. The effects of these fractionation processes on chemical structure, physico-chemical properties and antioxidant activity of extracted lignins were investigated. Lignins were characterized by their purity, carbohydrate composition, thermal stability, molecular weight and by Fourier transform infrared (FTIR), 1H and quantitative 13C nuclear magnetic resonance (NMR), adiabatic broadband {13C-1H} 2D heteronuclear (multiplicity edited) single quantum coherence (g-HSQCAD). The radical scavenging activity towards 2,2-diphenyl-1-picrylhydrazyl (DPPH) was also investigated. Formic/acetic acid pretreatment performed in milder conditions (80 °C for 3 h) gave a delignification percentage of 44.7% and soaking in aqueous ammonia 36.3%.Formic/acetic acid pretreatment performed in harsh conditions (107 °C for 3 h) was more effective for extensive delignification (86.5%) and delivered the most pure lignin (80%). The three lignin fractions contained carbohydrate in different extent: 3% for the lignin obtained after the formic/acetic acid pretreatment performed at 107 °C (FAL-107), 5.8% for the formic/acetic acid performed at 80 °C (FAL-80) and 13.7% for the ammonia lignin (AL). The acid pretreatment in harsh conditions (FAL-107) resulted in cleavage of β-O-4′ bonds and aromatic C-C. Repolymerisation was thought to originate from formation of new aromatic C-O linkages. Under milder conditions (FAL-80) less β-O-4′ linkages were broken and repolymerisation took place to a lesser extent. Ammonia lignin was not degraded to a significant extent and resulted in the highest weight average 3140 g mol⁻¹. Despite the fact of FAL-107 repolymerisation, significant phenolic hydroxyls remained free, explaining the greater antioxidant activity.     

Encapsulated energy-transfer cassettes with extremely well resolved fluorescent outputs

This paper concerns the development of water-compatible fluorescent imaging probes with tunable photonic properties that can be excited at a single wavelength. Bichromophoric cassettes 1a-1c consisting of a BODIPY donor and a cyanine acceptor were prepared using a simple synthetic route, and their photophysical properties were investigated. Upon excitation of the BODIPY moiety at 488 nm the excitation energy is transferred through an acetylene bridge to the cyanine dye acceptor, which emits light at approximately 600, 700, and 800 nm, i.e., with remarkable dispersions. This effect is facilitated by efficient energy transfer that gives a "quasi-Stokes" shift between 86 and 290 nm, opening a huge spectral window for imaging. The emissive properties of the cassettes depend on the energy-transfer (ET) mechanism: the faster the transfer, the more efficient it is. Measurements of rates of ET indicate that a through-bond ET takes place in the cassettes 1a and 1b that is 2 orders of magnitude faster than the classical through-space, F?rster ET. In the case of cassette 1c, however, both mechanisms are possible, and the rate measurements do not allow us to discern between them. Thus, the cassettes 1a-1c are well suited for multiplexing experiments in biotechnological methods that involve a single laser excitation source. However, for widespread application of these probes, their solubility in aqueous media must be improved. Consequently, the probes were encapsulated in calcium phosphate/silicate nanoparticles (diameter ca. 22 nm) that are freely dispersible in water. This encapsulation process resulted in only minor changes in the photophysical properties of the cassettes. The system based on cassette 1a was chosen to probe how effectively these nanoparticles could be used to deliver the dyes into cells. Encapsulated cassette 1a permeated Clone 9 rat liver cells, where it localized in the mitochondria and fluoresced through the acceptor part, i.e., red. Overall, this paper reports readily accessible, cyanine-based through-bond ET cassettes that are lypophilic but can be encapsulated to form nanoparticles that disperse freely in water. These particles can be used to enter cells and to label organelles.     

Infra-red assisted sintering of inkjet printed silver tracks on paper substrates

In this study, conductive silver features using inkjet printing have been successfully prepared and their sintering studied. Regarding conductivity, metallic inks are the most efficient available conductive inks, even if important drawbacks regarding the use of such inks in inkjet still exist. Indeed, the sintering step is an important limiting factor for the productivity and the substrate choice. An infrared (IR) drying method was experimented to optimize the sintering treatment time. Trials with glass and paper substrates were performed and proved that IR drying is interesting to optimize sintering. Indeed a similar level of resistance was obtained for conventional heating (200 °C, 5 min) and for IR radiations within a shorter treatment time (3 min). Moreover, the substrate temperature during the IR sintering treatment was controlled. The substrate appears to be a relevant parameter to optimize sintering because its thermal behaviour directly impacts on the treatment duration. And for the first time a sheet resistance of 1.9 Ω sq⁻¹ was obtained on paper substrate after only 2 min of IR treatment without any observation of substrate degradation. The evaluation of an electrical treatment on the sintering of a nanoparticle film was also performed using a corona pre-treatment. This lead appears to be interesting because the study proves that an electrical treatment can initiate the sintering of silver nanoparticles. The current flow generated by the corona electrodes certainly generates a local heating by dissipation of the conductive pattern. Finally, the solutions presented in this article allow reducing the sintering time of silver conductive inkjet inks. However mainly, it proves that using paper as substrate for such inks is now possible.