Ion mobility mass spectrometry enables the discrimination of positional isomers and the detection of conformers from cyclic oligosaccharides-metals supramolecular complexes.

Cyclic oligosaccharides are well known to interact with various metals, able to form supramolecular complexes with distinct sizes and shapes. However, the presence of various isomers in a sample, including positional isomers and conformers, can significantly impact molecular recognition, encapsulation ability and chemical reactivity. Therefore, it is crucial to have tools for deep samples probing and correlation establishments. The emerging ion mobility mass spectrometry (IM-MS) has the advantages to be rapid and sensitive, but is still in its infancy for the investigation of supramolecular assemblies. In the herein study, it was demonstrated that IM-MS is suitable to discriminate several isomers of cyclodextrins (CD)-metals complexes, used as cyclic oligosaccharide models. In this sense, we investigated branched 6-O-α-glucosyl- or 6-O-α-maltosyl-ß-cyclodextrins (G1-ß-CD and G2-ß-CD) and their purely cyclic isomers: CD8 (γ-CD) and CD9 (δ-CD). The corresponding collision cross section (CCS) values were deducted for the main positive singly and doubly charged species. Experimental CCS values were matched with models obtained from molecular modelling. The high mobility resolving power and resolution enabled discrimination of positional isomers, identification of various conformers and accurate relative content estimation. These results represent a milestone in the identification of carbohydrate conformers that cannot be easily reached by other approaches.

Fragmentation of DMPC Membranes by a Wedge-Shaped Amphiphilic Cyclodextrin into Bicellar-like Aggregates.

Small bilayer lipid aggregates such as bicelles provide useful isotropic or anisotropic membrane mimetics for structural studies of biological membranes. We have shown previously by deuterium NMR that a wedge-shaped amphiphilic derivative of trimethyl ßcyclodextrin anchored in deuterated DMPC-d27 bilayers through a lauryl acyl chain (TrimßMLC) is able to induce magnetic orientation and fragmentation of the multilamellar membranes. The fragmentation process fully detailed in the present paper is observed with 20% cyclodextrin derivative below 37 °C, where pure TrimßMLC self-assembles in water into large giant micellar structures. After deconvolution of a broad composite 2H NMR isotropic component, we propose a model where the DMPC membranes are progressively disrupted by TrimßMLC into small and large micellar aggregates depending whether they are extracted from the outer or inner layers of the liposomes. Below the fluid-to-gel transition of pure DMPC-d27 membranes (Tc = 21.5 °C), the micellar aggregates vanish progressively until complete extinction at 13 °C, with a probable release of pure TrimßMLC micelles leaving lipid bilayers in the gel phase doped with only a small amount of the cyclodextrin derivative. Bilayer fragmentation between Tc and 13 °C was also observed with 10% and 5% of TrimßMLC, with NMR spectra suggesting possible interactions of micellar aggregates with fluid-like lipids of the Pß' ripple phase. No membrane orientation and fragmentation was detected with unsaturated POPC membranes, which are able to accommodate the insertion of TrimßMLC without important perturbation. The data are discussed in relation to the formation of possible DMPC bicellar aggregates such as those known to occur after insertion of dihexanoylphosphatidylcholine (DHPC). These bicelles are in particular associated with similar deuterium NMR spectra exhibiting identical composite isotropic components which were never characterized before.

Probing topology of supramolecular complexes between cyclodextrins and alkali metals by ion mobility-mass spectrometry.

In this study, the size and shape of supramolecular assemblies between cyclo-oligosaccharides and proton, ammonium or a series of alkali metals by electrospray coupled to trapped ion mobility-mass spectrometry (ESI-TIMS) have investigated. Native cyclodextrins (CD) were selected as models, and collision cross section (CCS) values were deducted for the main positive singly and doubly charged species. Experimental CCS values were in good agreement with those obtained from molecular modeling. Due to the high mobility resolving power and resolution, it was possible to highlight the presence of various conformers. Also, TIMS allowed to discriminate and estimate the content of various orientations from non-covalent nanotubes-based CD, involving secondary/secondary rim hydroxyl groups (head-to head), primary/secondary rim (head-to-tail) hydroxyl groups or primary/primary rim (tail-to-tail) hydroxyl groups interactions. Such results pave the way for a better knowledge of the topology of cyclo-oligosaccharides based supramolecular complexes, demonstrating that TIMS can be a particularly attractive molecular descriptor.

Characterization of Grapevine Fanleaf Virus Isolates in 'Chardonnay' Vines Exhibiting Severe and Mild Symptoms in Two Vineyards.

Fanleaf degeneration is a complex viral disease of Vitis spp. that detrimentally impacts fruit yield and reduces the productive lifespan of most vineyards worldwide. In France, its main causal agent is grapevine fanleaf virus (GFLV). In the past, field experiments were conducted to explore cross-protection as a management strategy of fanleaf degeneration, but results were unsatisfactory because the mild virus strain negatively impacted fruit yield. In order to select new mild GFLV isolates, we examined two old 'Chardonnay' parcels harbouring vines with distinct phenotypes. Symptoms and agronomic performances were monitored over the four-year study on 21 individual vines that were classified into three categories: asymptomatic GFLV-free vines, GFLV-infected vines severely diseased and GFLV-infected vines displaying mild symptoms. The complete coding genomic sequences of GFLV isolates in infected vines was determined by high-throughput sequencing. Most grapevines were infected with multiple genetically divergent variants. While no specific molecular features were apparent for GFLV isolates from vines displaying mild symptoms, a genetic differentiation of GFLV populations depending on the vineyard parcel was observed. The mild symptomatic grapevines identified during this study were established in a greenhouse to recover GFLV variants of potential interest for cross-protection studies.

One-Pot Synthesis of Asymmetrically Difunctionalized Oligomaltosides by Cyclodextrin Ring Opening.

The synthesis of pure difunctionalized hexa-, hepta- and octamaltosides was performed by one-pot chemical reaction from perbenzoylated cyclodextrin. Oligomaltosides with azide, propargyl or allyl on reducing end and an unprotected hydroxyl group on non-reducing end were obtained from perbenzoylated α-, ß- and γ-cyclodextrin with 12 to 48 % yields.

First Steps to Rationalize Host-Guest Interaction between α-, ß-, and γ-Cyclodextrin and Divalent First-Row Transition and Post-transition Metals (Subgroups VIIB, VIIIB, and IIB).

Cyclodextrins (CDs) are cyclic oligosaccharides mainly composed of six, seven, and eight glucose units, so-called α-, ß-, and γ-CDs, respectively. They own a very particular molecular structure exhibiting hydrophilic features thanks to primary and secondary rims and delimiting a hydrophobic internal cavity. The latter can encapsulate organic compounds, but the former can form supramolecular complexes by hydrogen-bonding or electrostatic interactions. CDs have been used in catalytic processes to increase mass transfer in aqueous-organic two-phase systems or to prepare catalysts. In the last case, interaction between CDs and metal salts was considered to be a key point in obtaining highly active catalysts. Up to now, no work was reported on the investigation of factors affecting the binding of metal to CD. In the study herein, we present the favorable combination of electrospray ionization coupled to mass spectrometry [ESI-MS(/MS)] and density functional theory molecular modeling [B3LYP/Def2-SV(P)] to delineate some determinants governing the coordination of first-row divalent transition metals (Mn2+, Co2+, Ni2+, Cu2+, and Fe2+) and one post-transition metal (Zn2+) with α-, ß-, and γ-CDs. A large set of features concerning the metal itself (ionic radius, electron configuration, and spin state) as well as the complexes formed (the most stable conformer, relative abundance in MS, CE50 value in MS/MS, binding energy, effective coordination number, average bond lengths, binding site localization, bond dissociation energies, and natural bond orbital distribution) were screened. Taking into account all of these properties, various selectivity rankings have been delineated, portraying differential association/dissociation behaviors. Nonetheless, unique 3D topologies for each CD-metal complex were emphasized. The combination of these approaches brings a stone for building a compendium of molecular features to serve as a suitable descriptor or predictor for a better first round rationalization of catalytic activities.

Discrimination of isomeric trisaccharides and their relative quantification in honeys using trapped ion mobility spectrometry.

Carbohydrates play a myriad of critical roles as key intermediaries for energy storage, cell wall constituents, or also fuel for organisms. The deciphering of multiple structural isomers based on the monosaccharides composition (stereoisomers), the type of glycosidic linkages (connectivity) and the anomeric configuration (α and ß), remains a major analytical challenging task. The possibility to discriminate 13 underivatized isomeric trisaccharides were reported using electrospray ionization coupled to trapped ion mobility spectrometry (ESI-TIMS). After optimization of scan ratio enhancing both the mobility resolving power (R) and resolution (r), fingerprints from 5 different honeys were obtained. Seven trisaccharides with relative content varying from 1.5 to 58.3%, were identified. It was demonstrated that their relative content and/or their ratio could be used to ascertain origin of the honeys. Moreover, such direct approach constitutes an alternative tool to current longer chromatographic runs, paving the way to a transfer as suitable routine analysis.

First step to the improvement of the blood brain barrier passage of atazanavir encapsulated in sustainable bioorganic vesicles.

The blood - brain barrier (BBB) prevents the majority of therapeutic drugs from reaching the brain following intravenous or oral administration. In this context, polymer nanoparticles are a promising alternative to bypass the BBB and carry drugs to brain cells. Amphiphilic cyclodextrins can form self-assemblies whose nanoparticles have a 100-nm-diameter range and are thus able to encapsulate drugs for controlled release. Our goal is to propose an optimized chemical synthesis of amphiphilic cyclodextrin, which remains a challenging task which commonly leads to only a low-milligram level of the high purity compound. Such cyclodextrin derivatives were used to prepare vesicles and to study their ability to vectorize a drug through the BBB. As a result, we introduced a convergent synthesis for a family of lipophosphoramidyl permethylated ß-CDs (Lip-ß-CDs) with various chain lengths. It was demonstrated that mixed vesicles comprised of phosphatidylcholine (POPC) and LipCDs were able to encapsulate atazanavir (ATV), a well-known protease inhibitor used as an antiretroviral drug against HIV. We highlighted that neo-vesicles promote the penetration of ATV in endothelial cells of the BBB, presumably due to the low fusogenicity of Lip-ß-CDs.

New Lipidyl-Cyclodextrins Obtained by Ring Opening of Methyl Oleate Epoxide Using Ball Milling.

Bearing grafts based on fatty esters derivatives, lipidyl-cyclodextrins (L-CDs) are compounds able to form water-soluble nano-objects. In this context, bicatenary biobased lipidic-cyclodextrins of low DS were easily synthesized from a fatty ester epoxide by means of alternative methods (ball-milling conditions, use of enzymes). The ring opening reaction of methyl oleate epoxide needs ball-milling and is highly specific of cyclodextrins in solventless conditions. L-CDs are thus composed of complex mixtures that were deciphered by an extensive structural analysis using mainly mass spectrometry and NMR spectroscopy. In addition, as part of their potential use as vectors of active drugs, these products were submitted to an integrity study on in vitro model of the blood-brain-barrier (BBB) and the intestinal epithelium. No toxicity has been observed, suggesting that applications for the vectorization of active ingredients can be expected.

Ordering of Saturated and Unsaturated Lipid Membranes near Their Phase Transitions Induced by an Amphiphilic Cyclodextrin and Cholesterol.

When inserted in membranes of dimyristoyl phosphatidylcholine (DMPC), methylated ß-cyclodextrins with one (TrimßMLC) or two (TrimßDLC) lauryl acyl chains grafted onto the hydrophilic cavity exert a "cholesterol-like ordering effect", by straightening the acyl chains in the fluid phase at temperatures near the chain melting transition. This effect may be related to pretransitional events such as the "anomalous swelling" known to occur with saturated phosphatidylcholine membranes. To investigate this model, order profiles and bilayer thicknesses of DMPC and unsaturated 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) membranes containing amphiphilic cyclodextrins or cholesterol were determined by deuterium NMR. The pure lipid membranes display both a qualitatively similar chain ordering upon cooling in the fluid phase, more important at the chain extremity, which gets more pronounced near their fluid-to-gel transitions. Both membranes show a bilayer thickness increase by ∼0.5 Å just above their transition, as observed previously with saturated phosphatidylcholines of various chain lengths. Membrane-insertion of 5% TrimßMLC or cholesterol induces an important ordering of the DMPC acyl chains just above the transition, which is also more pronounced at the chain extremity. There is an additional increase of the bilayer thickness, most probably due to a deep insertion of these amphiphilic molecules, facilitated by increased bilayer softness in the anomalous swelling regime. These effects are more important with TrimßMLC than with cholesterol. By contrast, no enhanced acyl chain ordering was observed when approaching the transition of TrimßMLC-containing POPC membranes, as a possible consequence of an eventual lack of anomalous swelling in unsaturated lipid membranes. Insertion of higher concentrations of TrimßMLC was found to induce a magnetic orientation of the DMPC membranes in the fluid phase with 10% of this derivative, coupled with the appearance of a broad isotropic component when the concentration is raised to 20%. No membrane orientation or isotropic component was detected with TrimßMLC-containing POPC membranes.

The uncommon strong inhibition of α-glucosidase by multivalent glycoclusters based on cyclodextrin scaffolds.

The homeostasis disruption of d-glucose causes diabetes, a dramatic chronic disease worldwide. Type 1 diabetes is a successfully treatable form, where blood d-glucose is regulated by insulin treatment. In contrast type 2 diabetes, the non-insulin dependent kind, is problematic. The control of the d-glucose blood level via intestinal α-d-glucosidase inactivation can be achieved by using competitive inhibitors, such as iminosugars (e.g. acarbose) or sulfonium sugar derivatives (e.g. salacinol). Recently, an unprecedented result showed that multivalent diamond nanoparticles grafted with unmodified sugars displayed α-glucosidase inhibition at low micromolar concentrations. Herein we describe the synthesis of multivalent glycoclusters using cyclodextrins (CDs) as scaffolds and an assessment of their role as inhibitors of α-d-glucosidase. The glycoclusters were efficiently obtained from per-azido α, ß and γ-CD derivatives and propargyl glycosides using click-chemistry under microwave irradiation. The methodology was successfully applied to various protected and non-protected propargylated monosaccharides, including both O- and S-glycosides, giving clear evidence of its versatility. The targeted 6-per-glycosylated CDs were isolated in moderate to excellent yields (30-90%) by silica gel chromatography. The results showed inhibition of α-glucosidase from Saccharomyces cerevisiae with IC50 values in the 32-132 µM range, lower than that of acarbose (IC50 = ∼250 µM), a well-known competitive inhibitor used in the clinical treatment of type 2 diabetes. Preliminary experiments suggest a mixed-type non-competitive inhibition mode for these new glycoclusters.

A microscale double labelling of GAG oligosaccharides compatible with enzymatic treatment and mass spectrometry.

A novel double labelling of glycosaminoglycans (GAG) oligosaccharides by thia-Michael addition and deuterium incorporation at the non-reducing and reducing ends, respectively, was introduced. This was demonstrated to be both compatible with the heparin microgram scale and amenable for mass spectrometry analysis, without impairing enzymatic activities such as heparinase I and sulfatase HSulf-2.

Revealing cooperative binding of polycationic cyclodextrins with DNA oligomers by capillary electrophoresis coupled to mass spectrometry.

Gene delivery is critical for the development of nucleic acid-based therapies against a range of severe diseases. The conception of non-viral (semi)synthetic vectors with low cytotoxicity and virus-like efficiency is gathering a lot of efforts, but it represents a fantastic challenge still far from accomplishment. Carbohydrate-based scaffolds offer interesting features towards this end, such as easy availability, relatively cheap cost, tuning properties and a good biocompatibility. The lack of analytical methods providing quantitative and qualitative data on their binding properties with oligonucleotides (DNA/RNA), with a minimal time and sample consumption, represents a limitation for these channels. Here, we attempted to fill the gap by hyphenation of capillary electrophoresis with mass spectrometry (CE-MS). This coupling strategy allows discriminating free and complexed DNA oligomers with cationic cyclodextrins (CDs), determining the stoichiometry where the highest observed is always DNAn: n/3(CD), and unambiguously assigning the partners through m/z detection. Very reliable data were obtained with migration time within 5.5 (standard deviation < 0.5%) and 25 min (standard deviation < 1.1%) for UV and MS detection, respectively. Furthermore, varying the nitrogen/phosphorus ratio (N/P), key parameters relating to the thermodynamics e.g. the micro and macroscopic dissociation constants Kd and KD, respectively (both in low µM range) and the Gibbs free energy ΔG (-16.3 to -26.9 kJ mol-1), and also the cooperativity as Hill number (nH between 0.98 and 15.75) of the supramolecular process can be delineated, providing a unique tool for the high throughput screening and selection of efficient gene delivery carriers.

Toward a suitable structural analysis of gene delivery carrier based on polycationic carbohydrates by electron transfer dissociation tandem mass spectrometry.

Polycationic carbohydrates represent an attractive class of biomolecules for several applications and particularly as non viral gene delivery vectors. In this case, the establishment of structure-biological activity relationship requires sensitive and accurate characterization tools to both control and achieve fine structural deciphering. Electrospray-tandem mass spectrometry (ESI-MS/MS) appears as a suitable approach to address these questions. In the study herein, we have investigated the usefulness of electron transfer dissociation (ETD) to get structural data about five polycationic carbohydrates demonstrated as promising gene delivery agents. A particular attention was paid to determine the influence of charge states as well as both fluoranthene reaction time and supplementary activation (SA) on production of charge reduced species, fragmentation yield, varying from 2 to 62%, as well as to obtain the most higher both diversity and intensity of fragments, according to charge states and targeted compounds. ETD fragmentation appeared to be mainly directed toward pending group rather than carbohydrate cyclic scaffold leading to a partial sequencing for building blocks when amino groups are close to carbohydrate core, but allowing to complete structural deciphering of some of them, such as those including dithioureidocysteaminyl group which was not possible with CID only. Such findings clearly highlight the potential to help the rational choice of the suitable analytical conditions, according to the nature of the gene delivery molecules exhibiting polycationic features. Moreover, our ETD-MS/MS approach open the way to a fine sequencing/identification of grafted groups carried on various sets of oligo-/polysaccharides in various fields such as glycobiology or nanomaterials, even with unknown or questionable extraction, synthesis or modification steps.

Probing the common alkali metal affinity of native and variously methylated ß-cyclodextrins by combining electrospray-tandem mass spectrometry and molecular modeling.

In the study herein, we investigated the solution and gas phase affinity of native and variously methylated ß-cyclodextrins (CDs) as hosts towards three common alkali metals as guests namely lithium, sodium and potassium. For this purpose, two complementary approaches have been employed: electrospray-tandem mass spectrometry (ESI-MS/MS) with two energetic regimes: Collision Induced Dissociation (CID) and Higher Collision Dissociation (HCD), respectively, and DFT molecular modeling. These approaches have been achieved by taking into account the interaction of either one or two alkali metals with the host molecules. The results showed a good agreement between experimental and theoretical data. It was demonstrated that increasing the methylation degree strengthened the gas phase affinity towards all studied alkali metals. Furthermore, it was established that the cation selectivity was Na(+) > Li(+) > K(+) and Li(+) > Na(+) > K(+) for the solution and gas phase, respectively.

Cyclodextrin nanoassemblies: a promising tool for drug delivery.

Among the biodegradable and nontoxic compounds that can form nanoparticles for drug delivery, amphiphilic cyclodextrins are very promising. Apart from ionic cyclodextrins, which have been extensively studied and reviewed because of their application in gene delivery, our purpose is to provide a clear description of the supramolecular assemblies of nonionic amphiphilic cyclodextrins, which can form nanoassemblies for controlled drug release. Moreover, we focus on the relationship between their structure and physicochemical characteristics, which is crucial for self assembly and drug delivery. We also highlight the importance of the nanoparticle technology preparation for the stability and application of this nanodevice.

Cyclodextrin-grafted polymers functionalized with phosphanes: a new tool for aqueous organometallic catalysis.

New cyclodextrin (CD)-grafted polymers functionalized with water-soluble phosphanes were synthesized in three steps starting from polyNAS. Once characterized by NMR spectroscopy and size-exclusion chromatography, they were used as additives in Rh-catalyzed hydroformylation of 1-hexadecene. The combined supramolecular and coordinating properties of these polymers allowed increasing the catalytic activity of the reaction without affecting the selectivities.

A green approach to the synthesis of novel phytosphingolipidyl ß-cyclodextrin designed to interact with membranes.

This work reports the synthesis of a new family of mono-substituted amphiphilic cyclodextrins using a green methodology. Reactions using greener and safer catalysts with more environmentally friendly purification solvents were performed. Four unreported mono-substituted cyclodextrins bearing a phytosphingolipidyl chain and a fatty acid chain (C10, C12, C14 and C18) were successfully obtained with a promising yield.

Dynamic lipid lateral segregation driven by lauryl cyclodextrin interactions at the membrane surface.

Amphiphilic cyclodextrins, with a cholesterol anchor (ßChol) or an aspartic acid moiety esterified by two lauryl acyl chains (ßDLC), were designed to combine the inclusion ability of the cyclodextrin cavity with the carrier properties of model membranes. Their insertion in phosphatidylcholine bilayers induces a marked lateral phase separation into a pure lipid phase and a cyclodextrin-rich phase (LCD), organized as a 2D cyclodextrin network stabilized by intermolecular hydrogen bonds between the saccharide headgroups at the membrane surface (Roux, M.; Perly, B.; Djedaïni-Pilard, F. Self-Assemblies of Amphiphilic Cyclodextrins. Eur. Biophys. J.2007, 36, 861-867). We have replaced the dilauryl anchor by a single lauryl chain grafted onto a leucine residue, giving monolauryl-ß-cyclodextrin (ßMLC), which readily inserts into bilayers of chain-deuterated DMPC-d27. The removal of one lauryl acyl chain leads to a dynamic membrane insertion of this new cyclodextrin derivative, with significant lipid exchange on the deuterium NMR time scale between a loosely packed cyclodextrin-enriched phase (L'CD) and free lipid regions, yielding broadened two-component NMR spectra. Like the LCD phases, the cyclodextrin-enriched L'CD regions remain (partially) fluid below the DMPC-d27 main fluid-to-gel transition but do not undergo a clear transition toward a gel state, as observed at 14.5 °C in the LCD phase induced by the dilauryl derivative. Partially fluid lipids of the ßMLC-induced L'CD phase coexist with pure lipids in the Pß' gel phase with possible exchange between them until all of the lipids undergo a transition toward an Lß' gel state at around 7 °C. Trimethylated monolauryl-ß-cyclodextrins induce only an ordering of the lipid acyl chains just above the main transition, without any lateral phase separation. Similar chain ordering is also observed within the ßMLC-induced L'CD phase as a consequence of the deep membrane insertion of the monolauryl nonmethylated cyclodextrin derivative.

Discrimination of cyclic and linear oligosaccharides by tandem mass spectrometry using collision-induced dissociation (CID), pulsed-Q-dissociation (PQD) and the higher-energy C-trap dissociation modes.

RATIONALE: Carbohydrates have essential functions in living organisms and cells, but, due to the presence of numerous linkage combinations, substituent sites and possible conformations, they are the class of biomolecules which exhibits the huge structural diversity found in nature. Thereby, due to such diversity and poor ionization, their structural deciphering by mass spectrometry is still a very challenging task. METHODS: Here, we studied a series of linear and cyclic neutral oligosaccharides using electrospray with collision-induced dissociation (CID), pulsed-Q-dissociation (PQD) and the higher-energy C-trap dissociation (HCD) feature of a linear ion trap Orbitrap hybrid mass spectrometer (LTQ-Orbitrap). The collision energy necessary to obtain 50% fragmentation (CE(50) values) in CID, PQD and HCD was used to correlate both size and structures. RESULTS: The default settings for activation time and/or activation Q are the most appropriate, except for HCD, where 100 ms instead of 30 ms gave more intense fragment ions. PQD exhibits a 2-8-fold lower sensitivity than CID. HCD provides signals closer or slightly superior by 1.5-fold than PQD, and offers a more balanced ion distribution through the spectrum. Furthermore, HCD offers the possibility to make fine adjustments of the energy via the eV scale to further increase the yield of low-mass fragments. CONCLUSIONS: The complementarity of CID, PQD and HCD was clearly demonstrated by obtaining structural information on hexa-, hepta- and octasaccharides. Together, these results clearly indicate the usefulness of the CID/HCD pair for further structural deciphering, and analysis of more complex structures such as multi-antennary carbohydrates or glycoconjuguates alone or in mixture.