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Introduction
Publications
Publications (71)
Microalgae are a renewable and promising biomass for large-scale biofuel, food and nutrient production. However, their efficient exploitation depends on our knowledge of the cell wall composition and organization as it can limit access to high-value molecules. Here we provide an atomic-level model of the non-crystalline and water-insoluble glycopro...
The increasing occurrence of harmful algal blooms, mostly of the dinoflagellate Alexandrium catenella in Canada, profoundly disrupts mussel aquaculture. These filter-feeding shellfish feed on A. catenella and accumulate paralytic shellfish toxins, such as saxitoxin, in tissues, making them unsafe for human consumption. Algal toxins also have detrim...
Microalgae are a renewable and promising biomass for large-scale biofuel, food and nutrient production. However, their efficient exploitation depends on our knowledge of the cell wall composition and organization as it can limit access to high-value molecules. Here we provide an atomic-level model of the non-crystalline and insoluble glycoprotein-r...
Antimicrobial peptides stand as promising therapeutics to mitigate the global rise of antibiotic resistance. They generally act by perturbing the bacterial cell membrane, and are thus less likely to induce resistance. Since they are membrane-active molecules, it is critical to verify and understand their potential action towards eukaryotic cells to...
Microalgae are photosynthetic organisms widely distributed in nature and serve as a sustainable source of bioproducts. Their carbohydrate components are also promising candidates for bioenergy production and bioremediation, but the structural characterization of these heterogeneous polymers in cells remains a formidable problem. Here we present a w...
Cell labeling is a preliminary step in multiple biophysical approaches, including the solid-state nuclear magnetic resonance (NMR) study of bacteria in vivo. Deuterium solid-state NMR has been used in the past years to probe bacterial membranes and their interactions with antimicrobial peptides, following a standard labeling protocol. Recent result...
This work investigates the potential probiotic effect of marennine - a natural pigment produced by the diatom Haslea ostrearia - on Vibrio splendidus. These marine bacteria are often considered a threat for aquaculture; therefore, chemical antibiotics can be required to reduce bacterial outbreaks. In vivo ²H solid-state NMR was used to probe the ef...
We present a new membrane mimetic system using a membrane softening detergent commonly known as Tween 80 (TW80), to form oriented systems for solid-state NMR applications. TW80 is a fatty acid ester (oleate) of sorbitan polyethoxylate and a mild non-ionic surfactant. Phosphatidylcholine (PC)/TW80 model membrane systems were characterized by solid-s...
Starch is the most abundant energy storage molecule in plants and is an essential part of the human diet. This glucose polymer is composed of amorphous and crystalline domains in different forms (A and B types) with specific physicochemical properties that determine its bioavailability for an organism, as well as its value in the food industry. Usi...
The dysferlin membrane repair complex contains a small complex, S100A10-annexin A2, which initiates membrane repair by recruiting the protein AHNAK to the membrane, where it interacts via binding sites in the C-terminal region. However, no molecular data are available for the membrane binding of the various proteins involved in this complex. Theref...
Vibrio splendidus is a marine bacterium often considered as a threat in aquaculture hatcheries where it is responsible for mass mortality events, notably of bivalves’ larvae. This bacterium is highly adapted to dynamic salty ecosystems where it has become an opportunistic and resistant species. To characterize their membranes as a first and necessa...
Starch is the most abundant energy storage molecule in plants and is an essential part of the human diet. This glucose polymer is composed of amorphous and crystalline domains in different forms (A and B types) with specific physicochemical properties that determine its bioavailability for an organism, as well as its value in the food industry. Usi...
We study the local effect of the antimicrobial peptide Gramicidin A on bilayers composed of lipids or surfactants using nuclear magnetic resonance spectroscopy and wide-angle X-ray scattering, techniques that probe the orientational and positional order of the alkyl chains, respectively. The two types of order vary with temperature and peptide conc...
A variety of lipids that differ by their chains and headgroups are found in biomembranes. In addition to studying the overall membrane phase, determination of the structure, dynamics, and headgroup conformation of individual lipids in the mixture would be of great interest. We have thus developed, to our knowledge, a new approach using solid-state3...
In vivo or whole-cell solid-state NMR is an emerging field which faces tremendous challenges. In most cases, cell biochemistry does not allow the labelling of specific molecules and an in vivo study is thus hindered by the inherent difficulty of identifying, among a formidable number of resonances, those arising from a given molecule. In this work...
Discoveries relating to innate immunity and antimicrobial peptides (AMPs) granted Bruce Beutler and Jules Hoffmann a Nobel prize in medicine in 2011, and opened up new avenues for the development of therapies against infections, and even cancers. The mechanisms by which AMPs interact with, and ultimately disrupt, bacterial cell membranes is still,...
Bicelles (bilayered micelles) are model membranes used in the study of peptide structure and membrane interactions. They are traditionally made of long- and short-chain phospholipids, usually dimyristoylphosphatidylcholine (D14PC) and dihexanoyl-PC (D6PC). They are attractive membrane mimetics because of their composition and planar surface similar...
Biological molecular processes are often studied in model systems, which simplifies their inherent complexity but may cause investigators to lose sight of the effects of the molecular environment. Information obtained in this way must therefore be validated by experiments in the cell. NMR has been used to study biological cells since the early days...
This work proposes a new approach to characterize cell membranes in intact cells by 2H solid-state nuclear magnetic resonance (NMR) in only a few hours using magic-angle spinning (MAS) and spectral moment analysis. The method was first validated on model dipalmitoylphosphatidylcholine (DPPC) membranes, allowing the detection of lipid fluctuations b...
The structural biology of membrane proteins (MP) is hampered by the difficulty in producing and purifying them. A comprehensive analysis of protein databases revealed that 213 unique membrane protein structures have been obtained after production of the target protein in E. coli. The primary expression system used was the one based on the T7 RNA po...
Microalgae are unicellular organisms which plasma membrane is protected by a complex cell wall. The chemical nature of this barrier is important for taxonomic identification, but also for interactions with exogenous molecules such as contaminants. In this work, we have studied freshwater (Chlamydomonas reinhardtii) and marine (Pavlova lutheri and N...
Link: http://link.springer.com/chapter/10.1007/978-1-4939-0662-8_4
Structural biology of membrane proteins is hampered by the difficulty to express and purify them in a large amount. Despite recent progress in biophysical methods that have reduced the need of biological materials, membrane protein production remains a bottleneck in the field and w...
The vast majority of biophysical studies of membrane proteins (MPs) at the atomic scale are performed in vitro with preparations as homogeneous as possible, where the protein is isolated in a nonnative environment. MP samples for nuclear magnetic resonance (NMR) spectroscopy are no exception to the rule, in particular because purification helps to...
Bicelles are model membranes generally made of long-chain dimyristoyl-phosphatidylcholine (DMPC) and short-chain dihexanoyl-PC (DHPC). They are extensively used in the study of membrane interactions and structure determination of membrane-associated peptide since their composition and morphology mimic the widespread PC-rich natural eukaryotic membr...
The structural biology of membrane proteins (MP) is hampered by the difficulty in producing and purifying them. A comprehensive analysis of protein databases revealed that 213 unique membrane protein structures have been obtained after production of the target protein in E. coli. The primary expression system used was the one based on the T7 RNA po...
Fluorescence is a popular family of techniques used to study membranes, however recent systematic studies show that fluorescent probe behaviour can be altered by membrane composition, probe concentration, and the presence of other probes. Using deuterium nuclear magnetic resonance spec-troscopy (2 H NMR), we found that trace amounts of the carbocya...
Microalgae are unicellular organisms in which plasma membrane is protected by a complex cell wall. The chemical nature of this barrier is important not only for taxonomic identification, but also for interactions with exogenous molecules such as contaminants. In this work, we have studied freshwater (Chlamydomonas reinhardtii) and marine (Pavlova l...
Although cell-free expression is a relative newcomer to the biochemical toolbox, it has already been reviewed extensively, even in the more specialized cases such as membrane protein expression, nanolipoprotein particles, and applications to crystallography and nuclear magnetic resonance (NMR). Solid-state NMR is also a newcomer to the structural b...
The native environment of membrane proteins is complex and scientists have felt the need to simplify it to reduce the number of varying parameters. However, experimental problems can also arise from oversimplification which contributes to why membrane proteins are under-represented in the protein structure databank and why they were difficult to st...
Although solid-state NMR and cell-free expression have recently become standard methods in biology, the combination of the two is still at a very early stage of development. In this article, we will explore several approaches by which cell-free expression could help solid-state NMR in its quest for biomolecular structure and mechanism elucidation....
High-resolution structures of membrane proteins have so far been obtained mostly by X-ray crystallography, on samples where the protein is surrounded by detergent. Recent developments of solid-state NMR have opened the way to a new approach for the study of integral membrane proteins inside a membrane. At the same time, the extension of cell-free e...
Most studies reported until now on the magnetically alignable system formed by the binary mixtures of long- and short-chain lipids were based on the mixture of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (D14PC) and 1,2-dihexanoyl-sn-glycero-3-phosphocholine (D6PC) lipids. We have recently shown that a large part of the phase diagrams of this lipid...
A protocol is described for the reconstitution of a transmembrane beta-barrel protein domain, tOmpA, into lipid bicelles. tOmpA is the largest protein to be reconstituted in bicelles to date. Its insertion does not prevent bicelles from orienting with their plane either parallel or perpendicular to the magnetic field, depending on the absence or pr...
Phospholipid bilayers with over 20% cholesterol can form a liquid-ordered (l(o)) phase, which can be found in lateral domains, called rafts, in biomembranes. We show here that high-resolution (13)C and (1)H solid-state NMR are well suited to explore this phase, intermediate between gel and fluid. This approach can be applied to artificial or natura...
Most biological phospholipids contain at least one unsaturated alkyl chain. However, few order parameters of unsaturated lipids have been determined because of the difficulty associated with isotopic labeling of a double bond. Dipolar recoupling on axis with scaling and shape preservation (DROSS) is a solid-state nuclear magnetic resonance techniqu...
2H solid-state NMR experiments were performed under magic angle spinning on lipid bilayers oriented into nanotubes arrays, as a new method to assess the geometrical arrangement of the lipids. Orientational information is obtained from the intensities of the spinning sidebands. The lipid bilayers are formed by fusion of small unilamellar vesicles of...
Mixtures of dimyristoyl-phosphatidylcholine (DMPC) and dihexanoyl-phosphatidylcholine (DHPC) in water form disks also called bicelles and different bilayer organizations when the mol ratio of the two lipids and the temperature are varied. The spontaneous alignment in a magnetic field of these bilayers above the transition temperature T(m) of DMPC i...
In this Note we present the advantages of 1H magic-angle spinning nuclear magnetic resonance (MAS-NMR) for the investigation of surfactant suspensions via transverse relaxation rate (R2) measurements. 1H-relaxation rates can be determined by the classical CPMG method from high-resolution spectra obtained either under conditions of liquid-state NMR...
On page 2543, the bipolar scheme uses two gradient pulses for encoding, and two other gradient pulses for decoding. Thus, Equation 1 should be S/S0 = exp{-D4k2(D + 6t)}, rather than S/S0 = exp{-Dk2(D + 6t)}, as published. The incorrect expression would lead to an overestimation of the diffusion coeff. D by a factor of 4. This correction does not af...
On page 2543, the bipolar scheme uses two gradient pulses for encoding, and two other gradient pulses for decoding. Thus, Equation 1 should be S/S0 = exp{-D4k2(D + 6t)}, rather than S/S0 = exp{-Dk2(D + 6t)}, as published. The incorrect expression would lead to an overestimation of the diffusion coeff. D by a factor of 4. This correction does not af...
Membrane proteins classically are handled in aqueous solutions as complexes with detergents. The dissociating character of detergents, combined with the need to maintain an excess of them, frequently results in more or less rapid inactivation of the protein under study. Over the past few years, we have endeavored to develop a novel family of surfac...
The translational diffusion coefficient of an integral membrane protein/surfactant complex has been measured using a novel pulsed field gradient NMR method. In this new approach, the information about the localization of the molecules is temporarily stored in the form of longitudinal magnetization of isotopes with long spin-lattice relaxation times...
The (31)P-nuclear magnetic resonance chemical shift of phosphatidic acid in a membrane is sensitive to the lipid head group packing and can report qualitatively on membrane lateral compression near the aqueous interface. We have used high-resolution (31)P-nuclear magnetic resonance to evaluate the lateral compression on each side of asymmetrical li...
We have investigated the effect of the insertion of a triblock peptide (hydrophobic-hydrophilic hydrophobic) in a nonionic lamellar phase composed of C12E4, decane, and water, stabilized by bilayer thermal fluctuations. Circular dichroism shows the peptide to be unordered in water, whereas its hydrophilic part is rigid and organized in an a-helix i...
Polarization transfer is a key experiment for the detection of insensitive nuclei by NMR. Transfer in liquids is often achieved through J-coupling using the INEPT experiment, while in solids the dipolar coupling is used with cross polarization. Liquid crystals, including lipid membranes, are intermediate cases between solids and liquids. In the pre...
It has been reported that repetitive freeze-thaw cycles of aqueous suspensions of dioleoylphosphatidylcholine form vesicles with a diameter smaller than 200 nm. We have applied the same treatment to a series of phospholipid suspensions with particular emphasis on dioleoylphosphatidylcholine/dioleoylphosphatidic acid (DOPC/DOPA) mixtures. Freeze-fra...
The use of solid-state nuclear magnetic resonance (NMR) as a tool to determine the structure of membrane molecules is reviewed with a particular emphasis on techniques that provide information on orientation or order. Experiments reported here have been performed in membranes, rather than in micelles or organic solvents. Several ways to prepare and...
In the past fifteen years, interference between molecular dynamics and coherent manipulation of nuclear magnetization in nuclear magnetic resonance (NMR) experiments such as spin decoupling, cross-polarization or magic-angle spinning (MAS) have been identified and studied carefully. Recent experiments performed in our laboratory on model compounds...
Novel two-dimensional magic-angle spinning (2D MAS) NMR experiments designed to measure the magnitudes and signs of 13C−1H dipolar interactions in fluid phase lipid bilayers are presented. MAS is employed throughout the experiments while dipolar recoupling is achieved (by radio frequency irradiation) during the evolution period. Multiple 13C−1H dip...
For multilamellar suspensions of phospholipids, the 1H and 31P Nuclear Magnetic Resonance (NMR) spectra obtained with magic-angle spinning (MAS) exhibit resolution comparable to that
of sonicated vesicles. However, specific lipid head groups cannot be recognized in a lipid mixture using one-dimensional NMR
spectroscopy. We show here that the combin...
Phospholipid bilayers with over 20% cholesterol can form a liquid-ordered (lo) phase, which can be found in lateral domains, called rafts, in biomembranes. We show here that high-resolution 13C and 1H solid-state NMR are well suited to explore this phase, intermediate between gel and fluid. This approach can be applied to artificial or natural memb...
