Thierry Lefèvre

• Ph.D. in Biophysics
• Research Associate at Université Laval

Technological innovation is widely recognized as an endogenous element of capitalism driving economic growth and consumption. Although technological innovations have benefited human health, quality of life, and comfort, especially in high-income countries, uncontrolled industrialization of technological innovations and mass consumption exert strong...

Les défis associés à l’impact environnemental des énergies renouvelables sont redoutables et multiples, tant l’exploitation de formes d’énergie diffuses va nécessiter de remodeler nos modes de vie et nos infrastructures. Réduire leur impact environnemental est un impératif qui nécessite de mobiliser l’ensemble des leviers d’action disponibles.Au-de...

α-Synuclein, the protein responsible for Parkinson’s disease, contains a 12-residue long sequence, AS71-82, that is thought to play a crucial role in α-synuclein aggregation process. Neuronal membranes are direct interacting partners of α-synuclein and play a role in fibrillogenesis by providing a charged catalytic surface, notably from anionic pho...

Diatomite (DE) has attracted considerable attention owing to its abundance, low cost, and potential for a wide variety of applications. This work reports the development of mesoporous wool-ball-like (WBL) microspheres from natural DE through a simple hydrothermal treatment. We discovered that the presence of cetyltrimethylammonium bromide is a prer...

A linear spectral mapping technique was applied to monitor the growth of biomolecular absorption bands at the bio-interface of a nascent Pseudomonas fluorescens biofilm during and after interaction with a surface-adhered air bubble. Attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectra were obtained in different locations in a m...

Parkinson’s disease is an incurable neurodegenerative disorder caused by the aggregation of α-synuclein (AS). This amyloid protein contains a 12-residue-long segment, AS71-82, that triggers AS pathological aggregation. This peptide is then essential to better understand the polymorphism and the dynamics of formation of AS fibrillar structures. In t...

It is crucial to develop new natural sources of emulsifiers to substitute the synthetic molecules. An ideal emulsifying system exists in plants that is consisting of oil bodies proteins and phospholipids. In this study, Fourier transformed infrared (FTIR) spectroscopy was used to investigate the interactions between oil bodies proteins (OBP) and mo...

It is well established that amyloid proteins play a primary role in neurodegenerative diseases. Alzheimer’s, Parkinson’s, type II diabetes, and Creutzfeldt-Jakob’s diseases are part of a wider family encompassing more than 50 human pathologies related to aggregation of proteins. Although this field of research is thoroughly investigated, several as...

Recoverin is a protein involved in the phototransduction cascade by regulating the activity of rhodopsin kinase through a calcium-dependent binding process at the surface of rod outer segment disk membranes. We have investigated the interaction of recoverin with zwitterionic phosphatidylcholine bilayers, the major lipid component of the rod outer s...

Fluorinated peptides attract much interest in the biomedical area because they generally exhibit an enhanced stability compared to their hydrogenated counterparts and because fluorine atoms represent efficient probes to investigate peptide assemblies, especially in membranes. We previously designed and characterized a fluorinated peptide intended t...

Spider silks exhibit remarkable properties, among which the so-called supercontraction, a physical phenomenon by which fibers undergo a longitudinal shrinkage and a radial swelling when exposed to water. The process is marked by a significant decrease in chain orientation resulting from plasticisation of the amorphous phase. Despite several studies...

Spider aciniform (or wrapping) silk is the toughest of the seven types of spider silks/glue due to a combination of high elasticity and strength. Like most spider silk proteins (spidroins), aciniform spidroin (AcSp1) has a large core repetitive domain flanked by relatively short N- and C-terminal non-repetitive domains (the NTD and CTD, respectivel...

Recoverin is the only protein for which the phenomenon of calcium-myristoyl switch has been demonstrated without ambiguity. It is located in rod disk membranes where the highest content in polyunsaturated lipid acyl chains can be found. However, although essential to better understand the inactivation of the phototransduction process, the role of m...

Spider dragline silk is a semicrystalline polymer of great interest in materials science due to its unique mechanical properties and biocompatibility. Spun from the major ampullate glands, this type of silk possesses an exceptional combination of elasticity, strength and toughness. At the molecular level, spider silk is composed of fibrous proteins...

S'il est vrai que, au fil des décennies, les pays riches ont largement profité de la croissance économique, nous constatons que la logique de développement dominante constitue maintenant une menace pour notre civilisation. Au-delà de l'incurie et de la cupidité humaine, nous faisons preuve d'une incapacité chronique à lever les obstacles qui nous...

To plentifully benefit from its properties (mechanical, optical, biological) and its potential to manufacture green materials, the structure of spider silk has to be known accurately. To this aim, the major ampullate (MA) silk of Araneus diadematus (AD) and Nephila clavipes (NC) has been compared quantitatively in the liquid and fiber states using...

Recoverin is a protein involved in the phototransduction cascade by regulating the activity of rhodopsin kinase through a calcium-dependent binding process at the surface of rod outer segment disk membranes. Understanding how calcium modulates these interactions and how it interacts with anionic lipid membranes is necessary to get insights into the...

Our research project focuses on a specific peptide of α-synuclein which is an amyloid protein known to be involved in the neurodegenerative Parkinson’s disease. Aggregates of this protein are found in Parkinson’s disease patients’ brain, and more specifically, in the nerve tissues. This protein can be found in several forms, comprising monomers, ol...

Spider silk is one of the best illustrations of biomimetism. Thanks to a complex hierarchical structure, this fibre exhibits remarkable characteristics, especially renowned tensile properties. Silk filaments result from a complex spinning process that occurs in mild conditions of pressure and temperature, in aqueous solution and under optimised phy...

Spider silk exhibits remarkable properties, especially its well-known tensile performances. They rely on a complex nanostructured hierarchical organisation that studies progressively elucidate. Spider silk encompasses a vast range of fibres that exhibit diverse and captivating physical and biological characteristics. The full understanding of the r...

Thanatin is a cationic 21-residue antimicrobial and antifongical peptide found in the spined soldier bug Podisus maculiventris. It is admitted that it does not permeabilize membranes, but rather induces the agglutination of bacteria and inhibits cellular respiration. To clarify its mode of action, preliminary works have been devoted to the study of...

Spiders store spidroins in their silk glands as high concentration aqueous solutions, spinning these dopes into fibres with outstanding mechanical properties. Aciniform (or wrapping) silk is the toughest spider silk and is devoid of the short amino acid sequence motifs characteristic of the other spidroins. Using solution-state NMR spectroscopy, we...

Psoriasis is a chronic dermatosis that affects around 3% of the world's population. The etiology of this autoimmune pathology is not completely understood. The barrier function of psoriatic skin is known to be strongly altered, but the structural modifications at the origin of this dysfunction are not clear. To develop strategies to reduce symptoms...

Thanatin is a cationic 21-residue antimicrobial and antifongical peptide found in the spined soldier bug Podisus maculiventris. It is believed that it does not permeabilize membranes, but rather induces the agglutination of bacteria and inhibits cellular respiration. To clarify its mode of action, lipid vesicle organization and aggregation propensi...

Thanatin is a cationic 21-residue antimicrobial and antifongical peptide found in the spined soldier bug Podisus maculiventris. It is admitted that it does not permeabilize membranes, but rather induces the agglutination of bacteria and inhibits cellular respiration. To clarify its mode of action, preliminary works have been devoted to the study of...

To better understand the effect of mechanical stress during the spinning of silk, the protein orientation and conformation of Bombyx mori regenerated silk fibroin (RSF) films have been studied as a function of deformation in a static mode or in real time by tensile-Raman experiments and polarization modulation infrared linear dichroism (PM-IRLD), r...

Spider silk proteins undergo a complex series of molecular events before being converted into an outstanding hierarchically organized fiber. Recent literature has underlined the crucial role of the C-terminal domain in silk protein stability and fiber formation. However, the effect of pH remains to be clarified. We have thus developed an efficient...

The fibrillization of α-synuclein (α-syn) is involved in Parkinson's disease, a neurodegenerative disorder that affects four millions people in the world. The amino acid sequence 71-82 of this protein (VTGVTAVAQKTV) has appeared to be essential for fibril formation. In the present study, we have investigated the secondary structure and thermal stab...

Research in the field of bioengineered skin substitutes is motivated by the need to find new dressings for people affected by skin injuries (burns, diabetic ulcers), and to develop adequate skin models to test new formulations developed in vitro. Thanks to advances in tissue engineering, it is now possible to produce human skin substitutes, without...

Recoverin is a peripheral protein present in retinal photoreceptors. This protein is one of the fourteen members of the neuronal calcium sensor protein (NCS) family. These proteins have different functions such as phototransduction in the case of recoverin. The conformation of these proteins varies as a function of calcium concentration. At low Ca2...

To evaluate the structural stability of recoverin, a member of the neuronal calcium sensor family, the effect of temperature, myristoylation, and calcium:protein molar ratio on its secondary structure has been studied by transmission infrared spectroscopy. On the basis of the data, the protein predominantly adopts α-helical structures (∼50-55%) wit...

We have investigated the effect of pH, salts and shear on the hydrodynamical diameter of recombinant major ampullate (MA) rMaSpI silk proteins in solution as a function of time using (1) H solution NMR spectroscopy. The results indicate that the silk proteins in solution are composed of two diffusing populations, a high proportion of "native" solub...

The kinetics of adsorption of solubilized spider major ampullate (MA) silk fibers at the air-water interface as well as the molecular structure and mechanical properties of the interfacial films formed have been studied using various physical techniques. The data show that Nephila clavipes MA proteins progressively adsorb at the interface and ultim...

Silk fibers produced by nature are among the most interesting materials. Besides their high degree of biocompatibility, they are bioresorbable, ecologically friendly, and offer excellent mechanical properties. In particular, silks of spider and worm have aroused a huge interest as seen by the large literature on their structural organization [1,2]....

The β-amyloid fragment peptide 25-35 (Aβ25-35) is recognized as the cytotoxic sequence of the parent peptide Aβ. However, it remains unclear whether its neurotoxicity originates from its fibrillar form, how it interacts with lipid membranes, and whether cholesterol modulates these interactions. These questions have been addressed at a molecular lev...

In this study, we demonstrate the use of eco-friendly native spider silk as an efficient optical fiber in air, highly bent fibers, and physiological liquid. We also integrated the silk filament in a photonic chip made of polymer microstructures fabricated by UV lithography. The molding process is non-destructive for silk and leads to an efficient m...

The major ampullate (MA) silk of spider is known to be composed of oriented β-sheet nanocrystals dispersed within an amorphous matrix. The presence of an interphase has also been proposed, but it has not been reported for the fibroin of the silkworm Bombyx mori (B. mori). To obtain quantitative information regarding this third phase, the deuteratio...

Propagation properties of pristine silkworm are presented. The 5 microns-diameter fibers have been also integrated with polymer microstructures leading to successful optical coupling. These results pave the way for biophotonics applications.

Raman spectroscopy has long been proved to be a useful tool to study the conformation of protein-based materials such as silk. Thanks to recent developments, linearly polarized Raman spectromicroscopy has appeared very efficient to characterize the molecular structure of native single silk fibers and spinning dopes because it can provide informatio...

The spinning process of spiders can modulate the mechanical properties of their silk fibers. It is therefore of primary importance to understand what are the key elements of the spider spinning process to develop efficient industrial spinning processes. We have exhaustively investigated the native conformation of major ampullate silk (MaS) proteins...

Structural data relative to spider silk fibers such as the flagelliform (Flag) silk are fundamental to understand the origin of their outstanding mechanical properties. However, due to its small diameter and limited availability, experimental data relative to the structure of the Flag silk are almost nonexistent. Raman spectromicroscopy is one of t...

Structurally closely related spider silks, namely, major ampullate silk (MaS) reeled at 0.5 and 10 cm/s, minor ampullate silk (MiS), and cocoon silk have been investigated by solid-state nuclear magnetic resonance (NMR). These silks exhibit different mechanical properties that are not well explained with current structural data. NMR spectra confirm...

Spiders that spin orb webs secrete seven types of silk. Although the spinning process of the dragline thread is beginning to be understood, the molecular events that occur in spiders' opisthosomal glands, which produce the other fibers, are unknown due to a lack of data regarding their initial and final structures. Taking advantage of the efficienc...

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The alignment of β-sheets within spider dragline silk fibers is an important factor in their tensile strength and extensibility. We are using linear dichroism of the C 1s → π*amide transition measured using scanning transmission X-ray microscopy (STXM) to generate quantitative maps of the orientation parameters with 30 nm spatial resolution. Here w...

The effect of mechanical deformation on the polarized Raman spectra of a silk monofilament of the silkworm Bombyx mori has been studied in order to detect tensile stress-induced changes of the fibroin conformation and reorientation up to the breaking point. For this study, a motorized mechanical stretcher has been specifically designed to fit under...

Silk fibers harvested from the web, cocoon, and prey wrapping of the spider Nephila clavipes have been studied by polarized Raman spectromicroscopy. The technique is efficient to differentiate the various types of silk by probing monofilaments produced by the major ampullate (MA), minor ampullate (MI), cylindriform, flagelliform, and aciniform glan...

The dragline fiber of spiders is composed of two proteins, the major ampullate spidroins I and II (MaSpI and MaSpII). To better understand the assembly mechanism and the properties of these proteins, the adsorption behavior of the recombinant proteins of the spider Nephila clavipes produced by Nexia Biotechnologies Inc. has been studied at the air-...

The effect of high pressure homogenization on the properties of whey protein adsorbed on emulsion interface was determined by competitive adsorption with Tween 20, Fourier transform infrared (FT-IR) spectroscopy, and RP-HPLC. The amount of whey proteins desorbed by Tween 20 increased at higher pressure. The results of FT-IR spectroscopy showed that...

This chapter describes how different physical techniques can provide useful quantitative data for the evaluation of molecular orientation to emphasize their possibilities and limitations. It discusses the theory and procedures for orientation measurements and its quantitative characterization. The methods described in the chapter provide very accur...

The orientational and conformational transformation of the native liquid silk into a solid fiber in the major ampullate gland of the spider Nephila clavipes has been studied by Raman spectromicroscopy. The spectra show that the conformation of silk proteins in the glandular sac contains several secondary structure elements, which is consistent with...

Polarized attenuated total reflection (ATR) infrared spectroscopy is an efficient technique to determine the orientation and conformation of a large variety of samples, but it is more difficult to apply to very small specimens such as silk fibers. The Golden Gate single-reflection ATR accessory that uses diamond as an ATR element and a focalized be...

Bovine odorant-binding protein (bOBP), a member of the lipocalin family, presents the so-called 3D "domain-swapped" protein structure. In fact, in solution, it appears as a dimer in which each monomer is composed by the classical lipocalin fold, with a central beta-barrel followed by a stretch of residues and the alpha-helix domain protruding out o...

The conformational changes of whey proteins upon adsorption at the soy oil/water interface were investigated using Fourier transform infrared (FT-IR) spectroscopy. Significant changes were observed in the bands assigned to beta-sheets and alpha-helix structures following the adsorption of proteins at the oil/water interface. The remaining interfaci...

To understand the spinning process of dragline silk by spiders, the protein conformation before spinning has to be determined. Raman confocal spectromicroscopy has been used to study the conformation of the proteins in situ in the intact abdominal major ampullate gland of Nephila clavipes and Araneus diadematus spiders. The spectra obtained are typ...

Taking advantage of recent advances in polarized Raman microspectroscopy, and based on a rational decomposition of the amide I band, the conformation and orientation of proteins have been determined for cocoon silks of the silkworms Bombyx mori and Samia cynthia ricini and dragline silks of the spiders Nephila clavipes and Nephila edulis. This stud...

Raman microspectroscopy has been used to quantitatively study the effect of a mechanical deformation on the conformation and orientation of Samia cynthia ricini (S. c. ricini) silk fibroin. Samples were obtained from the aqueous solution stored in the silk gland and stretched at draw ratios (lambda) ranging from 0 to 11. Using an appropriate band d...

Separating effects due to molecular conformation from those due to orientation in the spectra of oriented samples obtained by Raman microspectroscopy is a complex issue. To solve this problem, we propose a procedure to calculate an orientation-insensitive spectrum (so-called isotropic spectrum) from polarized spectra obtained by Raman microspectros...

To optimize the properties of plasticized globular proteins films, a clear comprehension of the structure and molecular events occurring during film formation is required. In this work, the structural organization of beta-lactoglobulin (beta-lg) films plasticized with diethyelene glycol are investigated for the first time during the entire film for...

Raman microspectroscopy can provide high-quality spectra of single filaments having diameters smaller than 10 μm, allowing the determination of molecular orientation of very small samples. For systems with uniaxial symmetry, orientation can be quantitated by two order parameters, P2 and P4' that are calculated from intensity ratios of polarized spe...

Raman microspectroscopy has been used for the first time to determine quantitatively the orientation of the beta-sheets in silk monofilaments from Bombyx mori and Samia cynthia ricini silkworms, and from the spider Nephila edulis. It is shown that, for systems with uniaxial symmetry such as silk, it is possible to determine the order parameters P2...

of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

Two-dimensional (2D) correlation spectroscopy establishes correlations between intensity variations in a series of spectra obtained by the application of an external perturbation. However, spectral effects (wavenumber shift or bandwidth change) are known to generate apparent asynchronisms in 2D maps. Surprisingly, spectral effects are often neglect...

To obtain molecular insights into the action mode of antimicrobial activity of pediocin PA-1, the interactions between this bacteriocin and dimyristoylphosphatidylcholine (DMPC) or dimyristoylphosphatidylglycerol (DMPG) model membranes have been investigated in D2O at pD 6 by Fourier transform infrared spectroscopy. The interactions were monitored...

Oil-in-water emulsions stabilized with beta-lactoglobulin (beta-lg) were made using a homogenizer or a high-speed blender. The protein was studied by Fourier transform infrared (FTIR) spectroscopy in the raw emulsion, in the bulk phase, and at the interface, as a function of pH, oil content, and homogenizing pressure. Results show that the amount o...

Generalized two-dimensional correlation spectroscopy (2D-COS) establishes correlations between intensity variations within a series of ordered spectra generated by an external perturbation. The influence of the reference spectrum on the synchronicity has been investigated by using spectral simulations and mathematical analysis. With a two-state mod...

The effects of phytol on DPPC and OPPC multilayers were investigated using FT-IR and Raman spectroscopy. The results were compared with those obtained with -tocopherol (-T) and -tocopherol acetate (-TA). The chain packing was analyzed using Raman intensity ratios measured in the CH2 stretching region, whereas the number of gauche bonds introduced b...

The two-step crystallization of water in multilamellar vesicles (MLVs) of phosphatidylcholines has been investigated. The main crystallization occurs near –15 °C and involves bulk water. Contrary to unilamellar vesicles, a sub-zero phase transition is observed for MLVs at –40 °C that corresponds to the crystallization of interstitial water, as prov...

Interactions between beta-lactoglobulin (beta-lg) and dimyristoylphosphatidylglycerol (DMPG) bilayers were studied using one- and two-dimensional infrared spectroscopy above (pD 7.4) and below (pD 4.4) the protein's (beta-lg's) isoelectric point (pI=5.2). The aim of the study was threefold: (1) gain a better understanding of beta-lg-phospholipid in...

Fourier transform absorption infrared spectroscopy is a powerful and versatile tool used to determine the molecular structure of biomolecules. This technique is now widely used in biochemistry to study the conformation of biopolymers in aqueous solutions and complex systems. However, its enormous potential in the study of food biopolymers has yet t...

In order to reveal at a molecular level differences between fine-stranded and particulate gels, we present an Fourier transform infrared spectroscopic study of the thermal behavior of beta-lactoglobulin (beta-lg) in salt-free D(2)O solutions and low ionic strength at different pDs. Differences are found in the denaturation mechanism, in the unfolde...

Fourier transform infrared (FTIR) spectroscopy has been used to study, at a molecular level, the interactions between beta-lactoglobulin (BLG), the most abundant globular protein in milk, and some lipids (sphingomyelin, SM; dimyristoylphosphatidylcholine, DMPC; dipalmytoylphosphatidylcholine, DPPC; dimyristoylphosphatidylserine-sodium salt, DMPS; d...

In order to reveal at a molecular level differences between fine-stranded and particulate gels, we present an Fourier transform infrared spectroscopic study of the thermal behavior of β-lactoglobulin (β-lg) in salt-free D2O solutions and low ionic strength at different pDs. Differences are found in the denaturation mechanism, in the unfolded state...

Summary New aspects of β-Lactoglobulin (BLG) structure which have not previously been found by FT–IR spectroscopy are presented. The conformational changes of BLG and its heat-induced denaturation have been studied at low concentration and different pHs. First, it was found that the spectra of BLG in solution are concentration-dependent. Below 1%,...

Proteins and phospholipids are widely used as emulsifiers or stabilizers in emulsions, especially in the food industry. The interaction between these two kinds of molecules is an important factor controlling the formation, stability and texture of edible oil-in-water emulsions.

Effects of a-tocopherol ( a-T) and a-tocopheryl acetate ( a-TA) on dipalmiroyl-phosphatidylcholine (DPPC ) multilayers have been investigated by Fourier transform infrared and Raman spectroscopies. Earlier results have been confirmed by the temperature profiles built with the Raman intensity height ratios R = I 2 8 8 0 / I ~an~d~ r~ = 12935/128b8o0...

Aqueous solution of OPPC multilayers was studied by Raman scattering in a wide range of temperatures. A polymorphism similar to that of oleic acid was encountered. In particular, the LcII and LcI forms were identified. This polymorphism is largely due to the double bond of the oleyl chain in the sn-1 position. It was shown that the LcII form of OPP...

Solvation of lanric acid [CH3(CH2)10COOH] has been investigated in different solvents (apolar, polar-aprotic, and protic solvents) by infrared absorption and Raman scattering in a large molar ratio range in order to investigate the intermolecular interactions between fatty acids and molecules of different types of solvents. Temperature effects on t...