Simultaneous assessment of membrane bilayer structure and drug insertion by F solid-state NMR.

Fluorine-19 is an ideal nucleus for studying biological systems using NMR due to its rarity in biological environments and its favorable magnetic properties. In this work, we used a mixture of monofluorinated palmitic acids (PAs) as tracers to investigate the molecular interaction of the fluorinated drug rosuvastatin in model lipid membranes. More specifically, PAs labeled at the fourth and eighth carbon positions of their acyl chains were coincorporated in phospholipid bilayers to probe different depths of the hydrophobic core.

Molecular-level architecture of Chlamydomonas reinhardtii's glycoprotein-rich cell wall.

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 glycoprotein-rich cell wall of Chlamydomonas reinhardtii.

F solid-state NMR approaches to probe antimicrobial peptide interactions with membranes in whole cells.

To address the global problem of bacterial antibiotic resistance, antimicrobial peptides (AMPs) are considered promising therapeutic candidates due to their broad-spectrum and membrane-lytic activity. As preferential interactions with bacteria are crucial, it is equally important to investigate and understand their impact on eukaryotic cells. In this study, we employed F solid-state nuclear magnetic resonance (ssNMR) as a novel approach to examine the interaction of AMPs with whole red blood cells (RBCs).

Metabolomics and lipidomics reveal the effects of the toxic dinoflagellate Alexandrium catenella on immune cells of the blue mussel, Mytilus edulis.

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.

Peculiar Phosphonate Modifications of Velvet Worm Slime Revealed by Advanced Nuclear Magnetic Resonance and Mass Spectrometry.

Nature is rich with examples of highly specialized biological materials produced by organisms for functions, including defense, hunting, and protection. Along these lines, velvet worms (Onychophora) expel a protein-based slime used for hunting and defense that upon shearing and dehydration forms fibers as stiff as thermoplastics. These fibers can dissolve back into their precursor proteins in water, after which they can be drawn into new fibers, providing biological inspiration to design recyclable materials.

Development of a novel fluorescence assay for studying lipid bilayer perturbation induced by amyloidogenic peptides using cell plasma membrane vesicles.

Numerous pathophysiological conditions are associated with the misfolding and aggregation of proteins into insoluble amyloid fibrils. The mechanisms by which this process leads to cellular dysfunction remain elusive, though several hypotheses point toward the perturbation of the cell plasma membrane by pre-fibrillar intermediates and/or amyloid growth. However, current models to study membrane perturbations are largely limited to synthetic lipid vesicles and most of experimental approaches cannot be transposed to complex cell-derived plasma membrane systems.

In situ solid-state NMR study of antimicrobial peptide interactions with erythrocyte membranes.

Antimicrobial peptides are promising therapeutic agents 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. Because they are membrane-active molecules, it is critical to verify and understand their potential action toward eukaryotic cells to help design effective and safe drugs.

Growth-phase dependence of bacterial membrane lipid profile and labeling for in-cell solid-state NMR applications.

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 results from our laboratory on a slow-growing bacterium has shown the need to optimize this protocol, especially the bacterial growth time before harvest and the concentration of exogenous labeled fatty acids to be used for both Escherichia coli and Bacillus subtilis.

Identification and Quantification of Glycans in Whole Cells: Architecture of Microalgal Polysaccharides Described by Solid-State Nuclear Magnetic Resonance.

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 widely applicable protocol for identifying and quantifying the glycan content using magic-angle-spinning (MAS) solid-state NMR (ssNMR) spectroscopy, with validation from glycosyl linkage and composition analysis deduced from mass-spectrometry (MS).

Identification of transmissible proteotoxic oligomer-like fibrils that expand conformational diversity of amyloid assemblies.

Protein misfolding and amyloid deposition are associated with numerous diseases. The detailed characterization of the proteospecies mediating cell death remains elusive owing to the (supra)structural polymorphism and transient nature of the assemblies populating the amyloid pathway. Here we describe the identification of toxic amyloid fibrils with oligomer-like characteristics, which were assembled from an islet amyloid polypeptide (IAPP) derivative containing an Asn-to-Gln substitution (N21Q).

Investigating the action of the microalgal pigment marennine on Vibrio splendidus by in vivoH and P solid-state NMR.

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 vivoH solid-state NMR was used to probe the effects of marennine on the bacterial membrane in the exponential and stationary phases.

Extraction Improvement of the Bioactive Blue-Green Pigment "Marennine" from Diatom 's Blue Water: A Solid-Phase Method Based on Graphitic Matrices.

The compound "marennine" is a blue-green pigment produced by the benthic microalgae , with pathogenicity reduction activities against some bacteria and promising potential as a natural pigment in seafood industries. After decades of research, the chemical family of this compound still remains unclear, mainly because structural studies were impaired by the presence of co-extracted compounds in marennine isolates. To improve the purity of marennine extract, we developed a novel extraction method using a graphitic stationary phase, which provides various advantages over the previous procedure using tandem ultrafiltration.

Magnetically-orientable Tween-based model membranes for NMR studies of proteins.

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-state NMR and FTIR spectroscopy.

Labelling strategy and membrane characterization of marine bacteria Vibrio splendidus by in vivoH NMR.

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 necessary step toward studying bacterial interactions with diverse molecules, we established a labelling protocol for in vivoH solid-state nuclear magnetic resonance (SS-NMR) analysis of V.

Unambiguous Ex Situ and in Cell 2D C Solid-State NMR Characterization of Starch and Its Constituents.

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. Using two-dimensional (2D) high resolution solid-state nuclear magnetic resonance (SS-NMR) on C-labelled starches that were obtained from microalgae, we established a complete and unambiguous assignment for starch and its constituents (amylopectin and amylose) in the two crystalline forms and in the amorphous state.

A New Method of Assessing Lipid Mixtures by P Magic-Angle Spinning NMR.

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-state P NMR, magic-angle spinning, and chemical-shift anisotropy (CSA) recoupling, using an altered version of the recoupling of chemical shift anisotropy (ROCSA) pulse sequence, here penned PROCSA.

Whole cell solid-state NMR study of Chlamydomonas reinhardtii microalgae.

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 we examined the possibility of studying, by solid-state NMR, the model organism Chlamydomonas reinhardtii fully and non-specifically C labelled.

Comparative study of the structure and interaction of the pore helices of the hERG and Kv1.5 potassium channels in model membranes.

The hERG channel is a voltage-gated potassium channel found in cardiomyocytes that contributes to the repolarization of the cell membrane following the cardiac action potential, an important step in the regulation of the cardiac cycle. The lipids surrounding K channels have been shown to play a key role in their regulation, with anionic lipids shown to alter gating properties. In this study, we investigate how anionic lipids interact with the pore helix of hERG and compare the results with those from Kv1.

Magnetically Oriented Bicelles with Monoalkylphosphocholines: Versatile Membrane Mimetics for Nuclear Magnetic Resonance Applications.

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 their composition and planar surface are similar to the native membrane environment.

Interaction of the antimicrobial peptides caerin 1.1 and aurein 1.2 with intact bacteria by H solid-state NMR.

Nuclear magnetic resonance (NMR) is commonly used to probe the effect of antimicrobial agents on bacterial membranes using model membrane systems. Ideally, considering the complexity of membranes, the interaction of molecules with membranes should be studied in vivo. The interactions of two antimicrobial peptides (AMPs) with intact Escherichia coli and Bacillus subtilis were investigated using deuterium solid-state NMR.

In-Cell Solid-State NMR: An Emerging Technique for the Study of Biological Membranes.

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 of its development.

A (2)H magic-angle spinning solid-state NMR characterisation of lipid membranes in intact bacteria.

This work proposes a new approach to characterize cell membranes in intact cells by (2)H 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 below the main transition temperature. Then the lipid dynamics in Escherichia coli membranes was compared in bacteria grown under different diets.

Synthesis and solvodynamic diameter measurements of closely related mannodendrimers for the study of multivalent carbohydrate-protein interactions.

This paper describes the synthesis of three closely related families of mannopyranoside-containing dendrimers for the purpose of studying subtle structural parameters involved in the measurements of multivalent carbohydrate-protein binding interactions. Toward this goal, two trimers 5 and 9, three 9-mers 12, 17, 21, and one 27-mer 23, varying by the number of atoms separating the anomeric and the core carbons, were synthesized using azide-alkyne cycloaddition (CuAAc). Compound 23 was prepared by an efficient convergent strategy.

Identification of lipid and saccharide constituents of whole microalgal cells by ¹³C solid-state NMR.

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 lutheri and Nannochloropsis oculata) microalgae with different cell wall characteristics.