1,721,158 research outputs found
Invisible fluorinated materials for optical sensing
No full textFluorinated materials can be produced in order to combine an amorphous, homogenous structure and a refractive index very close to that of water. When in contact with aqueous solutions, such materials become barely visible. In these conditions, the adhesion of small amounts of molecules on their surface induces an optical signal that can be easily detected. This principle was exploited to realize novel label-free optical biosensors using either a dispersion of nanoparticles or a prism of fluorinated polymers as sensing substrates. The detection of specific molecular compounds in solution was achieved by suitable functionalization of the surface of the fluorinated materials
Kinetics of intramolecular contact formation in disordered peptides and unfolded proteins
No full textThe formation of intramolecular contacts between distant residues is, perhaps, the simplest among the elementary processes taking place during the folding of a protein. Quenching of the triplet state of tryptophan by close contact with cysteine after nanosecond laser excitation has been used to measure both equilibrium (reaction-limited) and dynamic (diffusion-limited) contact formation rates in model peptides and engineered proteins. The triplet quenching data and FRET end-to-end distances are analyzed by means of a chain model with realistic backbone conformations and simplified hard-sphere interaction between the residues. The effect of amino acid sequence on the chain swelling is discussed
Emerging applications of label-free optical biosensors
Full text linkInnovative technical solutions to realize optical biosensors with improved performance are continuously proposed. Progress in material fabrication enables developing novel substrates with enhanced optical responses. At the same time, the increased spectrum of available biomolecular tools, ranging from highly specific receptors to engineered bioconjugated polymers, facilitates the preparation of sensing surfaces with controlled functionality. What remains often unclear is to which extent this continuous innovation provides effective breakthroughs for specific applications. In this review, we address this challenging question for the class of label-free optical biosensors, which can provide a direct signal upon molecular binding without using secondary probes. Label-free biosensors have become a consolidated approach for the characterization and screening of molecular interactions in research laboratories. However, in the last decade, several examples of other applications with high potential impact have been proposed. We review the recent advances in label-free optical biosensing technology by focusing on the potential competitive advantage provided in selected emerging applications, grouped on the basis of the target type. In particular, direct and real-time detection allows the development of simpler, compact, and rapid analytical methods for different kinds of targets, from proteins to DNA and viruses. The lack of secondary interactions facilitates the binding of small-molecule targets and minimizes the perturbation in single-molecule detection. Moreover, the intrinsic versatility of label-free sensing makes it an ideal platform to be integrated with biomolecular machinery with innovative functionality, as in case of the molecular tools provided by DNA nanotechnology
The correlation of biochemical monitoring versus umbilical flow velocity measurements in the human fetus
No full textMemory effects from topological connectivity of nematic liquid crystals confined in porous materials
No full textIt is known that confinement of nematic liquid crystals (NLC) into porous structures gives rise to systems having strong and intriguing memory effects. Some work has been done on NLC hosting nanostructured gels, but a general understanding of these effects is still missing.
Prompted by experimental results, we have studied by computer simulation, the behavior of NLC confined in porous media with various bicontinuous geometries and providing perpendicular anchoring of the nematic director at their surface. We find that in all structures, frustration induced by the conflicting boundary conditions induces the formation of disclination defect lines that are stabilized by the very geometry of the porous media. Various sets of defect arrangements are possible, a property that makes the system highly metastable and capable of memorizing the alignment forced by external fields. We determine which geometrical features of the porous matrices maximize metastability and how they affect the dynamics of NLC. We provide the basics for designing NLC-based heterogeneous structures targeting specific electro-optical properties
Phenotype of the terminal transferase-positive cells in human foetal liver and bone-marrow: analysis with monoclonal antibodies.
No full textField-induced anti-nematic ordering in assemblies of anisotropically polarizable particles
Full text linkWe have investigated the effects of dipolar interactions in a lattice system of anisotropically polarizable particles in the presence of an external field both by Monte Carlo computer simulations and through a mean-field analysis. In a specific range of low temperature, large external field and large particle density, a novel staggered nematic structure is found, in which two intercalated sublattices have different nematic order parameters. First- and second-order phase transition lines, connected at a tricritical point, enclose the anti-nematic phase in the temperature-density plane
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