Protein sizing with Differential Dynamic Microscopy

Introduced more than fifty years ago, dynamic light scattering is routinely used to determine the size distribution of colloidal suspensions, as well as of macromolecules in solution, such as proteins, nucleic acids, and their complexes. More recently, differential dynamic microscopy has been proposed as a way to perform dynamic light scattering experiments with a microscope, with much less stringent constraints in terms of cleanliness of the optical surfaces, but a potentially lower sensitivity due to the use of camera-based detectors. In this work, we push bright-field differential dynamic microscopy beyond known limits and show it to be sufficiently sensitive to size small macromolecules in diluted solutions. By considering solutions of three different proteins (Bovine Serum Albumin, Lysozyme, and Pepsin), we accurately determine the diffusion coefficient and hydrodynamic radius of both single proteins and small protein aggregates down to concentrations of a few milligrams per milliliter. In addition, we present preliminary results showing unexplored potential for the determination of virial coefficients. Our results are in excellent agreement with the ones obtained in parallel with a state-of-the-art commercial dynamic light scattering setup, showing that differential dynamic microscopy represents a valuable alternative for rapid, label-free protein sizing with an optical microscope

Road traffic pollution and childhood leukemia: a nationwide case-control study in Italy

Background The association of childhood leukemia with traffic pollution was considered in a number of studies from 1989 onwards, with results not entirely consistent and little information regarding subtypes. Aim of the study We used the data of the Italian SETIL case-control on childhood leukemia to explore the risk by leukemia subtypes associated to exposure to vehicular traffic. Methods We included in the analyses 648 cases of childhood leukemia (565 Acute lymphoblastic–ALL and 80 Acute non lymphoblastic-AnLL) and 980 controls. Information on traffic exposure was collected from questionnaire interviews and from the geocoding of house addresses, for all periods of life of the children. Results We observed an increase in risk for AnLL, and at a lower extent for ALL, with indicators of exposure to traffic pollutants. In particular, the risk was associated to the report of closeness of the house to traffic lights and to the passage of trucks (OR: 1.76; 95% CI 1.03–3.01 for ALL and 6.35; 95% CI 2.59–15.6 for AnLL). The association was shown also in the analyses limited to AML and in the stratified analyses and in respect to the house in different period of life. Conclusions Results from the SETIL study provide some support to the association of traffic related exposure and risk for AnLL, but at a lesser extent for ALL. Our conclusion highlights the need for leukemia type specific analyses in future studies. Results support the need of controlling exposure from traffic pollution, even if knowledge is not complete

Mechanosensing and Sphingolipid-Docking Mediate Lipopeptide-Induced Immunity in Arabidopsis

Bacteria-derived lipopeptides are immunogenic triggers of host defenses in metazoans and plants. Root-associated rhizobacteria produce cyclic lipopeptides that activate systemically induced resistance (IR) against microbial infection in various plants. How these molecules are perceived by plant cells remains elusive. Here, we reveal that immunity activation inArabidopsis thalianaby the lipopeptide elicitor surfactin is mediated by docking into specific sphingolipid-enriched domains and relies on host membrane deformation and subsequent activation of mechanosensitive ion channels. This mechanism leads to host defense potentiation and resistance to the necrotrophB. cinereabut is distinct from host pattern recognition receptor-mediated immune activation and reminiscent of damage-induced plant immunity

Interferometric investigation of the gas-state monolayer of monorhamnolipid adsorbing at an oil/water interface.

We present a study on biosurfactant uptake at the interface of a millimeter-sized drop of squalene in water, by a recently developed differential interferometric technique. The technique allows detecting capillary waves, with amplitudes of the order of 10-9 m, excited on the surface of the drop by an electric field in the order of 5V/cm. By studying the resonant surface modes of the drop it is possible to assess the interfacial properties as a function of the surfactant concentration in the water bulk. The technique allows to follow the adsorption process at extremely low surfactant concentration, not accessible by other methods, investigating the gas state in the π-A diagrams of 2D amphiphilic monolayers

Attractive Interaction between Fully Charged Lipid Bilayers in a Strongly Confined Geometry

International audienc

Carbohydrate-carbohydrate interaction drives the preferential insertion of dirhamnolipid into glycosphingolipid enriched membranes

Rhamnolipids (RLs) are among the most important biosurfactants produced by microorganisms, and have been widely investigated because of their multiple biological activities. Their action appears to depend on their structural interference with lipid membranes, therefore several studies have been performed to investigate this aspect. We studied by X-ray scattering, neutron reflectometry and molecular dynamic simulations the insertion of dirhamnolipid (diRL), the most abundant RL, in model cellular membranes made of phospholipids and glycosphingolipids. In our model systems the affinity of diRL to the membrane is highly promoted by the presence of the glycosphingolipids and molecular dynamics simulations unveil that this evidence is related to sugar-sugar attractive interactions at the membrane surface. Our results improve the understanding of the plethora of activities associated with RLs, also opening new perspectives in their selective use for pharmaceutical and cosmetics formulations. Additionally, they shed light on the still debated role of carbohydrate-carbohydrate interactions as driving force for molecular contacts at membrane surface