Search results for "covalent bond"
showing 10 items of 305 documents
Direct subphthalocyanine conjugation to bombesin vs. indirect conjugation to its lipidic nanocarrier
2016
International audience; Bombesin (BBN) was covalently bound to graftable subphthalocyanine (SubPc) or to a cholesterol derivative, a component of a liposome that encapsulates non-graftable SubPc. The latter bioconjugation approach was suitable to address the stability of SubPc and was achieved by copper-free click-chemistry on the outer-face of the liposome. Liposomes were purified (FPLC) and then analyzed in size (outer diameter about 60 nm measured by DLS). In vitro binding studies allowed to determine the IC50 13.9 nM for one component of the liposome, cholesterol, conjugated to BBN. Hence, azido- (or alkynyl-) liposomes give fluorophores with no reactive functional group available on th…
Clickable poly-L-lysine for the formation of biorecognition surfaces
2019
Biomolecules are immobilized onto surfaces employing the fast and stable adsorption of poly-l-lysine (PLL) polymers and the versatile copper-free click chemistry reactions. This method provides the combined advantages of versatile surface adsorption with density control using polyelectrolytes and of the covalent and orthogonal immobilization of biomolecules with higher reaction rates and improved yields of click chemistry. Using DNA attachment as a proof of concept, control over the DNA probe density and applicability in electrochemical detection are presented.
Polymerization of Lipid and Lysolipid Like Diacetylenes in Monolayers and Liposomes
1980
The bilayer type lipid membrane has a variety of important functions that are necessary in order to sustain life. A lot of these functions have been studied with artificial model membranes such as black lipid membranes (BLM) or liposomes. A great disadvantage of all these models is their instability — BLM for instance can only exist for minutes or hours and only under the presence of water. Therefore, it was the aim of this work to produce simple model membranes that can retain their structure under a variety of test conditions. The route chosen to obtain such membranes was through the polymerization of lipid and lysolipid like molecules in monolayers at the gas-water interface or in liposo…
Dynamic covalent urea bonds and their potential for development of self-healing polymer materials
2019
Self-healing polymer materials have drawn rapidly increasing interest over the last decade, and have been studied and used in an ever-increasing range of applications. Herein, we successfully make the covalent urea bond – a pinnacle of stability due to strong resonance effects – dynamic in nature through mediation of zinc salts. The dynamic covalent character of urea in the presence of zinc ions is confirmed through dissociation reaction experiments and quantum chemical calculations of small-molecule model urea compounds. In line with our experiments, the modelling results suggest that the presence of zinc ions speeds up the reaction of urea dissociation by two orders of magnitude via the f…
Functionalisation of MoS2 2D layers with diarylethene molecules
2021
Functionalisation of two dimensional (2D) materials with stimuli-responsive molecules has been scarcely investigated. Here, MoS2 layers obtained by chemical exfoliation are covalently and non-covalently functionalised using two photoswitchable diarylethene derivatives under their open- and closed-ring isomers. The choice of these light-responsive molecules is based on their excellent thermal irreversibility and fatigue resistance. The characterisation of the resultant molecular/2D heterostructures proves the successful anchoring of the molecules by both approaches as well as the influence that the driving interaction has in the photoswitching behaviour of the diarylethene isomers after thei…
Covalent and non-covalent coupling of a Au102 nanocluster with a fluorophore: energy transfer, quenching and intracellular pH sensing
2021
Interactions between an atomically precise gold nanocluster Au102(p-MBA)44 (p-MBA = para mercaptobenzoic acid) and a fluorescent organic dye molecule (KU, azadioxatriangulenium) are studied. In solution, the constituents form spontaneously a weakly bound complex leading to quenching of fluorescence of the KU dye via energy transfer. The KU can be separated from the complex by lowering pH, leading to recovery of fluorescence, which forms a basis for an optical reversible pH sensor. However, the sensor is not a stable entity, which could be delivered inside cells. For this purpose, a covalently bound hybrid is synthesized by linking the KU dye to the ligand layer of the cluster via an ester b…
Langmuir films and Langmuir-Blodgett multilayers incorporating mechanically-threaded molecules-pseudorotaxanes
1996
This paper describes the synthesis of a π-electron rich aromatic lipid containing a polyether thread intercepted by a 1,5-dioxynaphthalene moiety. The terminus of one end of the polyether is a methoxyl group and the other a glycerol unit linked via the 2-oxo position, while the 1,3-oxo functions are covalently attached to octadecyl chains. This compound, when cospread at the air-water interface with the tetracationic cyclophane, cyclobis(paraquat-p-phenylene), and the phospholipid, dimyristoylphosphatidic acid, as its monoanion, forms self-assembled pseudorotaxanes which are self-organized into a two-dimensional supramolecular array at the interface. The electrostatic interactions between t…
Tunable Interaction Strength and Nature of the S···Br Halogen Bonds in [(Thione)Br2] Systems
2015
The strength and nature of the S···Br and Br···Br interactions were systematically tuned by altering the electron donor properties of the thione group. Three new halogen-bonded compounds, [(N-methylbenzothiazole-2-thione)Br2]·0.5CH2Cl2 (1), [(2(3H)-benzothiazolethione)Br2] (2), and [(2-benzimidazolethione)Br]·[Br3] (3), were synthesized and studied structurally by using X-ray crystallography and computationally by using charge density analysis based on QTAIM calculations. Analysis of the interaction strength indicated a formation of surprisingly strong S···Br halogen bonds in 1 (−104 kJ mol–1, and RBrS = 0.64) and 2 (−116 kJ mol–1, and RBrS = 0.63) with a substantial covalent contribution. …
Covalently Binding of Bovine Serum Albumin to Unsaturated Poly(Globalide-Co-ε-Caprolactone) Nanoparticles by Thiol-Ene Reactions.
2019
When nanoparticles (NPs) are introduced to a biological fluid, different proteins (and other biomolecules) rapidly get adsorbed onto their surface, forming a protein corona capable of giving to the NPs a new "identity" and determine their biological fate. Protein-nanoparticle conjugation can be used in order to promote specific interactions between living systems and nanocarriers. Non-covalent conjugates are less stable and more susceptible to desorption in biological media, which makes the development of engineered nanoparticle surfaces by covalent attachment an interesting topic. In this work, the surface of poly(globalide-co-e-caprolactone) (PGlCL) nanoparticles containing double bonds i…
Silanol-POSS as dispersing agents for carbon nanotubes in polyamide
2017
Silanol polyhedrad oligomeric silsesquiosane terminated with phenyl rings (phPOSS) has been considered as dispersing agent for carbon nanotubes (CNTs) in polyamide (PA) matrix. Two different approaches have been followed for the introduction of the phPOSS molecules: a âclassicalâ approach which involves the introduction of the dispersing agent during the melt mixing, and an âinnovativeâ approach, consisting in the immobilization, either covalent and non-covalent, of phPOSS molecules onto CNTs surface. The properties of PA-based nanocomposites, containing free phPOSS molecules and phPOSS molecules immobilized onto the CNTs outer surface, have been evaluated through rheological, mecha…