Giovanna Fragneto

Giovanna Fragneto
Institut Laue-Langevin · Science Division

DPhil

About

214
Publications
22,841
Reads
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5,435
Citations
Citations since 2016
68 Research Items
2467 Citations
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20162017201820192020202120220100200300400
20162017201820192020202120220100200300400
Introduction
Giovanna Fragneto currently works at the Science Division, Institut Laue-Langevin. Giovanna does research in Physical Chemistry, Surface Chemistry and Biophysics.
Additional affiliations
February 2015 - present
Institut Laue-Langevin
Position
  • Large Scale Structures group leader
September 2013 - present
Institut Laue-Langevin
Position
  • Head of Soft Matter Science and Support
January 2008 - January 2015
Institut Laue-Langevin
Position
  • Fellow

Publications

Publications (214)
Article
Full-text available
Self-initiated photografting and photopolymerization (SI-PGP) uses UV illumination to graft polymers to surfaces without additional photoinitiators using the monomers as initiators, "inimers". A wider use of this method is obstructed by a lack of understanding of the resulting, presumably heterogeneous, polymer structure and of the parallel degrada...
Article
Biosurfactants represent an ecosustainable alternative to conventional surfactants, allowing to reduce the environmental impact arising from the increasing production of industrial surfactant-containing formulations. In the present work, the physico-chemical properties of the aqueous solutions of rhamnolipids (Rha) are compared to those of sodium l...
Article
Full-text available
Supported lipid bilayers (SLBs) are commonly used as model systems mimicking biological membranes. Recently, we reported a new method to produce SLBs with incorporated membrane proteins, which is based on the application of peptide discs [Luchini et al., Analytical Chemistry, 2020, 92, 1081-1088]. Peptide discs are small discoidal particles compose...
Article
Phenylketonuria (PKU) is a metabolic disorder connected to an excess of phenylalanine (Phe) in the blood and tissues, with neurological consequences. The disease's molecular bases seem to be related to the accumulation of Phe at the cell membrane surface. Radiological outcomes in the brain demonstrate decreased water diffusivity in white matter, in...
Article
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Hypothesis: Acyl-L-carnitines (CnLCs) are potentially important as biosurfactants in drug delivery and tissue engineering due to their good biocompatibility. However, little is currently known about the basic interfacial behavior underlying their technological applications. Following our previous characterization of their solution aggregation and a...
Article
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The fourth enzymatic reaction in the de novo pyrimidine biosynthesis, the oxidation of dihydroorotate to orotate, is catalyzed by dihydroorotate dehydrogenase (DHODH). Enzymes belonging to the DHODH Class II are membrane-bound proteins that use ubiquinones as their electron acceptors. We have designed this study to understand the interaction of an...
Article
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Coronavirus disease-2019 (COVID-19), a potentially lethal respiratory illness caused by the coronavirus SARS-CoV-2, emerged in the end of 2019 and has since spread aggressively across the globe. A thorough understanding of the molecular mechanisms of cellular infection by coronaviruses is therefore of utmost importance. A critical stage in infectio...
Preprint
Full-text available
Coronavirus disease-2019 (COVID-19), a lethal respiratory illness caused by the coronavirus SARS-CoV-2, emerged in the end of 2019 and has since spread aggressively across the globe. A thorough understanding of the molecular mechanisms of cellular infection by coronaviruses is therefore of utmost importance. A critical stage in infection is the fus...
Article
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SARS-CoV-2 spike proteins are responsible for the membrane fusion event, which allows the virus to enter the host cell and cause infection. This process starts with the binding of the spike extramembrane domain to the angiotensin-converting enzyme 2 (ACE2), a membrane receptor highly abundant in the lungs. In this study, the extramembrane domain of...
Article
A key to the development of lipid membrane-based devices is a fundamental understanding of how the molecular structure of the lipid bilayer membrane is influenced by the type of lipids used to build the membrane. This is particularly important when membrane proteins are included in these devices since the precise lipid environment affects the abili...
Preprint
Full-text available
SARS-CoV-2 spike proteins are responsible for the membrane fusion event, which allows the virus to enter the host cell and cause infection. This process starts with the binding of the spike extramembrane domain to the angiotensin-converting enzyme 2 (ACE2), a membrane receptor highly abundant in the lungs. In this study, the extramembrane domain of...
Article
The properties of lipid monolayers at the interface between two immiscible electrolyte solutions (ITIES) have attracted much attention over the last 30 years. This is mainly because of the biological relevance of lipids and the possibility of controlling ion and electron transfer across one leaflet of a cellular membrane. In the last decade, the el...
Article
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Eukaryotic and prokaryotic cell membranes are difficult to characterize directly with biophysical methods. Membrane model systems, that include fewer molecular species, are therefore often used to reproduce their fundamental chemical and physical properties. In this context, natural lipid mixtures directly extracted from cells are a valuable resour...
Article
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The plant plasma membrane (PM) is an essential barrier between the cell and the external environment, controlling signal perception and transmission. It consists of an asymmetrical lipid bilayer made up of three different lipid classes: sphingolipids, sterols and phospholipids. The Glycosyl Inositol Phosphoryl Ceramides (GIPCs), representing up to...
Article
The proton pump transmembrane protein bacteriorhodopsin was successfully incorporated into planar floating lipid bilayers in gel and fluid phases, by applying a detergent-mediated incorporation method. The method was optimized on single supported bilayers by using quartz crystal microbalance, atomic force and fluorescence microscopy techniques. Neu...
Article
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We have characterized and compared the structures of ergosterol-and cholesterol-containing 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) membranes before and after interaction with the amphiphilic antifungal drug amphotericin B (AmB) using neutron reflection. AmB inserts into both pure POPC and sterol-containing membranes in the lipid cha...
Article
Supported lipid bilayers (SLBs) are commonly used to investigate the structure and dynamics of biological membranes. Vesicle fusion is a widely exploited process to produce SLBs. However, this process becomes less favoured when the vesicles contain complex lipid mixtures, e.g. natural lipid extracts. In these cases, it is often necessary to change...
Article
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Theoretical simulations have predicted that a lipid bilayer forms a stable superstructure when a sheet of graphene is inserted in its hydrophobic core. We experimentally produced for the first time a lipid–graphene–lipid assembly by combining the Langmuir–Blodgett and the Langmuir–Schaefer methods. Graphene is sandwiched and remains flat within the...
Article
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The physiological and pathological roles of nascent amyloid beta (Aβ) monomers are still debated in the literature. Their involvement in the pathological route of Alzheimer's Disease (AD) is currently considered to be the most relevant, triggered by their aggregation into structured oligomers, a toxic species. Recently, it has been suggested that n...
Preprint
Full-text available
The plant plasma membrane (PM) is an essential barrier between the cell and the external environment. The PM is crucial for signal perception and transmission. It consists of an asymmetrical lipid bilayer made up of three different lipid classes: sphingolipids, sterols and phospholipids. The most abundant sphingolipids in the plant PM are the Glyco...
Article
Polyunsaturated omega-3 fatty acid docosahexaenoic acid (DHA) is found in very high concentrations in a few peculiar tissues, suggesting that it must have a specialized role. DHA was proposed to affect the function of the cell membrane and related proteins through an indirect mechanism of action, based on the DHA-phospholipid effects on the lipid b...
Article
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Molecular dynamics (MD) simulations, stochastic optical reconstruction microscopy (STORM) and neutron reflection (NR) are combined to explore how antimicrobial peptides (AMPs) can be designed to promote the formation of nanoaggregates into bacterial membranes and impose effective bactericidal actions. Changes in the hydrophobicity of the designed A...
Article
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The potency of anesthesia was directly linked to the partitioning of the drug molecules in cell membranes by Meyer and Overton. Many molecules interact with lipid bilayers and lead to structural and functional changes. It remains an open question which change in membrane properties is responsible for a potential anesthetic effect or if anesthetics...
Article
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Nanoparticles (NPs) are increasingly exploited as diagnostic and therapeutic devices in medicine. Among them, superparamagnetic nanoparticles (SPIONs) represent very promising tools for magnetic resonance imaging, local heaters for hyperthermia and nanoplatforms for multimodal imaging and theranostic. However, the use of NPs, including SPIONs, in m...
Article
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Neutron diffraction was used to study the behavior of water present in phospholipid multilamellar stacks from 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC) at cryogenic temperatures. Evidence was found for the existence of a highly viscous phase of water that exists between 180 and 220 K based on the observation that water can leave the i...
Article
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Sterols regulate several physico-chemical properties of biological membranes that are considered to be linked to function. Ergosterol is the main sterol molecule found in the cell membranes of yeasts and other fungi. Like the cholesterol found in mammalian cells, ergosterol has been proposed to have an ordering and condensing effect on saturated ph...
Article
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Bare interfaces between water and hydrophobic media like air or oil are of fundamental scientific interest and of great relevance for numerous applications. A number of observations involving water/hydrophobic interfaces have, however, eluded a consensus mechanistic interpretation so far. Recent theoretical studies ascribe these phenomena to an int...
Article
We investigate the interaction between highly charged lipid bilayers in presence of monovalent ions. Neutron and x-ray reflectivity experiments show that the water layer between like-charged bilayers is significantly thinner than for zwitterionic lipids, demonstrating the existence of counter-intuitive electrostatic attractive interaction between t...
Preprint
We investigate the interaction between highly charged lipid bilayers in presence of monovalent counterions. Neutron and X-ray reflectivity experiments show that the water layer between like-charged bilayers is thinner than for zwitterionic lipids, demonstrating the existence of counter-intuitive electrostatic attractive interaction between them. Th...
Article
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In article number 1805046, Jaakko Akola, Marco Maccarini, and co‐workers use neutron reflectometry and molecular dynamics simulations to quantify how the interaction between cationic functionalized gold nanoparticles and model lipid membranes depends on temperature and the lipid charge. The combination of scattering studies and the computational ap...
Article
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Understanding the molecular mechanisms governing nanoparticle–membrane interactions is of prime importance for drug delivery and biomedical applications. Neutron reflectometry (NR) experiments are combined with atomistic and coarse‐grained molecular dynamics (MD) simulations to study the interaction between cationic gold nanoparticles (AuNPs) and m...
Article
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Monolayer-protected gold nanoparticles are emerging as promising candidates for drug delivery due to their ability to permeate through plasma membranes. Understanding the molecular mechanisms of such complex systems is crucial to control cell permeation and to develop efficient biomedical delivery applications based on nanoscale gold nanoparticles....
Article
End-grafted poly[ethylene glycol] (PEG) brushes are widely used in order to suppress undesired protein adsorption to surfaces exposed to blood or other biological fluids. The specific adsorption of antibodies (Abs) to PEG brushes associated with PEG’s antigenicity is drawing increasing attention because it can affect clinical applications. Here, th...
Article
Cells, the basic units of living organisms, are well delineated and separated from the external environment by membranes. Capable of both enclosing the cellular constituents and allowing exchanges with the outside world, these membranes are only a few nanometers thick. All the membranes in a human body cover an area of a few hectares, but account f...
Article
Stable stimuli-responsive emulsions between oil and water are formed with an amphiphilic block copolymer bearing polystyrene (PS) and poly(dimethylaminoethyl methacrylate) (PDMAEMA) moieties. Different kinds of emulsions like direct, multiple or inverse ones are reproducibly formed as a function of chemical parameters such as p H and salt concentra...
Article
We investigated the insertion of small potassium (K+) channel proteins (KcvMA-1D and KcvNTS) into model membranes and the lipid-protein structural interference, combining neutron reflectometry and electrophysiology. Neutron reflectometry experiments showed how the transverse structure and mechanical properties of the bilayer were modified, upon ins...
Article
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The outer surfaces of Gram-negative bacteria are composed of lipopolysaccharide (LPS) molecules exposing oligo- and polysaccharides to the aqueous environment. This unique, structurally complex biological interface is of great scientific interest as it mediates the interaction of bacteria with antimicrobial agents as well as with neighboring bacter...
Article
The structural investigation of cellular membranes requires access to model systems where the molecular complexity is representative of the cellular environment and that allow for the exploitation of structural techniques. Neutron scattering, and in particular neutron diffraction can provide unique and detailed information on the structure of lipid...
Article
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Different bacterial types and their living environments can lead to different saturations in the chains of their membrane lipids. Such structural differences may influence the efficacy of antibiotics that target bacterial membranes. In this work, the effects of acyl chain saturation on the binding of an antimicrobial peptide G4 have been examined a...
Article
Poly[ethylene glycol] (PEG) brushes are reputed for their ability to prevent undesired protein adsorption to material surfaces exposed to biological fluids. Here, protein adsorption out of human blood serum onto PEG brushes anchored to solid-supported lipid monolayers was characterized by neutron reflectometry, yielding volume fraction profiles of...
Article
We have set-up a facile approach for fabrication of supports with tailored nanoporosity for immobilization of enzymes. To this aim block copolymers self-assembly has been used to prepare nanostructured thin films with well-defined architecture containing pores of tailorable size delimited by walls with tailorable degree of hydrophilicity. In partic...
Article
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The interaction between surfaces displaying end-grafted hydrophilic polymer brushes plays important roles in biology and in many wet-technological applications. In this context, the conformation of the brushes upon their mutual approach is crucial, because it affects interaction forces and the brushes' shear-tribological properties. While this aspe...
Article
The increased biosynthesis of lysyl-phosphatidylglycerol in Staphylococcus aureus when cultured under conditions of mild acidity and the resultant increased proportion of this lipid in the plasma membrane of the bacterium, alters the physico-chemical properties of lipid bilayers in a manner which is itself dependent upon environmental pH. Clinicall...
Article
Polysaccharides are known to modify binding of proteins at interfaces and this paper describes studies of these interactions and how they are modified by pH. Specifically, the adsorption of human serum albumin on to polystyrene latex and to silica is described, focusing on how this is affected by hyaluronan. Experiments were designed to test how su...
Article
Hypothesis: It is known that nanoparticles (NPs) in a biological fluid are immediately coated by a protein corona (PC), composed of a hard (strongly bounded) and a soft (loosely associated) layers, which represents the real nano-interface interacting with the cellular membrane in vivo. In this regard, supported lipid bilayers (SLB) have extensivel...
Article
The preparation and investigation of model membranes is deserving growing interest both for the physics of complex systems, and for biology. The need of simplified models should preserve mimicking the qualifying characteristics of biological membranes, and keep non-invasive and detailed description. As a main feature, biological membranes are non-h...
Article
In vivo lipid membranes interact with rough supramolecular structures such as protein clusters and fibrils. How these features whose size ranges from a few nanometers to a few tens of nanometers impact lipid and protein mobility is still investigated. Here, we study supported phospholipid bilayers, a unique biomimetic model, deposited on etched sur...
Article
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The knowledge of the mechanism used by vectors to gain access to cell interiors is key to the development of effective drug delivery tools for different pathologies. The role of the initial interaction with the membrane bilayer is widely recognized, although not fully understood. We use neutron reflectivity experiments and internalization studies w...
Article
Synchrotron radiation reflectometry was used to access the transverse structure of model membranes under the action of the human sialidase NEU2, down to the Ångström length scale. Model membranes were designed to mimic the lipid composition of so-called Glycosphingolipids Enriched Microdomains (GEMs), which are membrane platforms specifically enric...
Article
Islet amyloid polypeptide (IAPP) is responsible for cell depletion in the pancreatic islets of Langherans, and for multiple pathological consequences encountered by patients suffering from type 2 Diabetes Mellitus. We have examined the amyloidogenicity and cytotoxic mechanisms of this peptide by investigating model-membrane permeation and structura...
Article
The safe application of nanotechnology devices in biomedicine requires fundamental understanding on how they interact with and affect the different components of biological systems. In this respect, the cellular membrane, the cell envelope, certainly represents an important target or barrier for nanosystems. Here we report on the interaction betwee...
Article
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Significance Interfacial molecular layers are a major component of all biological matter and also play key roles in most biotechnological applications. The understanding of important biological processes involving molecular layers typically relies on detailed structural insight. We demonstrate that standing-wave X-ray fluorescence enables the label...
Article
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The effect of ac electric fields on the elasticity of supported lipid bilayers is investigated at the microscopic level using grazing incidence synchrotron x-ray scattering. A strong decrease in the membrane tension up to 1 mN=m and a dramatic increase of its effective rigidity up to 300 kBT are observed for local electric potentials seen by the me...
Article
Knowledge of the (supra)molecular structure of an interface that contains amphiphilic ligand molecules is necessary for a full understanding of ion transfer during solvent extraction. Even if molecular dynamics already yield some insight in the molecular configurations in solution, hardly any experimental data giving access to distributions of both...
Article
Knowledge of the (supra)molecular structure of an interface that contains amphiphilic ligand molecules is necessary for a full understanding of ion transfer during solvent extraction. Even if molecular dynamics already yield some insight in the molecular configurations in solution, hardly any experimental data giving access to distributions of both...
Article
Full-text available
The role of first-stage β–amyloid aggregation in the development of the Alzheimer disease, is widely accepted but still unclear. Intimate interaction with the cell membrane is invoked. We designed Neutron Reflectometry experiments to reveal the existence and extent of the interaction between β–amyloid (Aβ) peptides and a lone customized biomimetic...
Article
The activity of the potent but highly toxic antifungal drug Amphotericin B (AmB), used intravenously to treat systemic fungal and parasitic infections, is widely accepted to result from its specific interaction with the fungal sterol ergosterol. While the effect of sterols on AmB activity has been intensely investigated, the role of membrane phosph...
Article
Full-text available
We have resolved the molecular structure of a bulk oil/water interface that contains amphiphilic ligand molecules using a combination of X-ray and neutron reflectivity measurements for the first time. This new capability can greatly impact future work in the field of ion separation by phase transfer, i.e. liquid/liquid extraction.