Information Guide: Cyprus. March 2015

A guide to information sources on the Republic of Cyprus, with hyperlinks to information within European Sources Online and on external websites (For other language versions of this record click on the original url

Following protein aggregation using track-etched nanopore

International audienc

Nanopore Technology : From polymer film to irradiation to the detection and study of (bio)macromolecules

International audienc

Physisorbed poly(ethylene oxide) is a robust tether for AFM-based single-molecule force spectroscopy

Atomic force microscopy (AFM)-based single-molecule force spectroscopy is a prevalent tool for the exploration of individual (bio)molecules, providing exquisite information on many molecular-level processes. For example, proteins, DNA, polysaccharides, supramolecular polymers and polyelectrolytes have been investigated, revealing details about the strength of intramolecular interactions, folding and unfolding pathways, mechanics, conformational changes, reactivity, kinetics, etc. For each particular system under investigation, the experimental design is a decisive phase that often involves a multistep chemical protocol, including grafting, derivatization, coupling, (de-)protection, and other functionalization reactions. Procedures of sample preparation are often complex and time-consuming. Hence, there is a need for new general platforms allowing for straightforward sample preparation adapted to single-molecule studies, i.e. a tight attachment to both the substrate and the tip, and a low density to favor single-molecule detection. We report here on the use of poly(ethylene oxide) (PEO) as a tether to probe various properties of individual molecules. The polymeric linker acts as a handle that stably binds to the AFM tip. The simple adsorption of poly(ethylene oxide) to the tip is versatile and provides an appropriate system configuration for the investigation of many different biological and synthetic molecular systems. To attest for this versatility and adequacy with advanced single-molecule investigation, we present different examples of PEO-mediated studies about the unfolding of a synthetic peptide, the mechanochemical behavior of a molecular machine and finally the stability of a metallo-supramolecular complexed polymer. All the requirements for the study of peptide conformation, tiny molecular machines or metallo-supramolecular interactions in solution are here fulfilled. More generally, this method based on non-covalent sorption of PEO on an AFM tip, can be implemented in a wide range of solvents, for the study of many intra- or intermolecular phenomena at the single-molecule level over orders of magnitude of force loading rates. Connecting PEO tethers to a very broad variety of (bio)molecules is a facile and versatile route. The commercial availability of many different functional PEOs makes this tethering strategy even more accessible

Mechanisms of Heparin-Induced Tau Aggregation Revealed by a Single Nanopore

International audienceProtein aggregation is involved in many diseases, including Parkinson's and Alzheimer's. The latter is characterized by intraneuronal deposition of amyloid aggregates composed of the tau protein. Although large and insoluble aggregates are typically found in affected brains, intermediate soluble oligomers are thought to represent crucial species for toxicity and spreading. Nanopore sensors constitute an emerging technology that allows the detection of the size and populations of molecular assembly present in a sample. Here, we employed conical nanopores to obtain the particle distributions during tau aggregation. We identified three distinct populations, monomers, oligomers, and fibrils, which we could quantify along the aggregation process. By comparing tau wild type with a mutant carrying the disease-associated P301L mutation, we showed that the latter mutation promotes the formation of oligomers. We furthermore highlighted that the P301L mutation promotes fibril breakage. This work demonstrates that conical nanopore is a powerful tool to measure and quantify transient protein aggregate intermediates

Metal alloy solid-state nanopores for single nanoparticle detection

International audienc

Unexpected Hard Protein Behavior of BSA on Gold Nanoparticle Caused by Resveratrol

International audienceThe understanding of the interactions between nanomaterials, biomolecules, and polyphenols is fundamental in food chemistry, toxicology, and new emerging fields, such as nanomedicine. Here, we investigated the effect of the resveratrol, a principal actor in drug-delivery application on the interaction between bovine serum albumin (BSA), employed as a vector for the delivery of polyphenol drugs, and gold nanoparticle (gNP), the most promising tool in theranostic applications. Through a combination of experimental techniques, which includes an initial evaluation by dynamic light scattering and surface plasmon resonance spectroscopy, we were able to evaluate the evolution of the gold nanoparticle aggregation with increasing ionic strength and the consequences of the BSA and resveratrol addition. To investigate the mechanisms of the interactions, we pursued at the single-molecule level using solid-state nanopore and fluorescence correlation spectroscopy. Our results show that without resveratrol, the BSA is adsorbed on the gNP in water or saline solution. In the presence of resveratrol, the BSA is normally absorbed on gNP in water, but the salt addition leads to its desorption. The resveratrol clearly plays a fundamental role, changing the protein behavior and making the BSA adsorption a reversible process in the presence of salt