Electron Transfer Dissociation of Alkali-Cationized Phosphatidylcholines Allows Easy Double Bonds and sn-1/sn-2 Localizations.

Rationale: The emergence of new mass spectrometry (MS) dissociation methods has highlighted lipid isomers as new biomarkers. Only a few commercial methods without derivatization are available to characterize phosphatidylcholines (PCs) at the isomeric level. We propose to use electron transfer dissociation (ETD) as a method to determine the position of both double bonds and stereo numbering (sn) on glycerol for PC species.

Structure and functional impact of glycosaminoglycan modification of HSulf-2 endosulfatase revealed by atomic force microscopy and mass spectrometry.

The human sulfatase HSulf-2 is one of only two known endosulfatases that play a decisive role in modulating the binding properties of heparan sulfate proteoglycans on the cell surface and in the extracellular matrix. Recently, HSulf-2 was shown to exhibit an unusual post-translational modification consisting of a sulfated glycosaminoglycan chain. This study describes the structural characterization of this glycosaminoglycan (GAG) and provides new data on its impact on the catalytic properties of HSulf-2.

Comprehensive structural assignment of glycosaminoglycan oligo- and polysaccharides by protein nanopore.

Glycosaminoglycans are highly anionic functional polysaccharides with information content in their structure that plays a major role in the communication between the cell and the extracellular environment. The study presented here reports the label-free detection and analysis of glycosaminoglycan molecules at the single molecule level using sensing by biological nanopore, thus addressing the need to decipher structural information in oligo- and polysaccharide sequences, which remains a major challenge for glycoscience. We demonstrate that a wild-type aerolysin nanopore can detect and characterize glycosaminoglycan oligosaccharides with various sulfate patterns, osidic bonds and epimers of uronic acid residues.

Dereplication of Acetogenins from by Combining Tandem Mass Spectrometry after Lithium and Copper Postcolumn Cationization and Molecular Networks.

Annonaceous acetogenins are natural products held responsible for atypical Parkinsonism due to chronic consumption in traditional medicine or as food, leading to the development of analytical strategies for their complete chemical characterization in complex mixtures. Characterization by tandem mass spectrometry (MS/MS) of acetogenins using collision-induced dissociation from lithium adducts provides additional structural information compared to protonated or sodiated species such as ketone location on the acetogenin backbone. However, very low intensity diagnostic ions together with the lack of extensive structural information regarding position of OH and THF substituents limit this approach.

Discrimination of sulfated isomers of chondroitin sulfate disaccharides by HILIC-MS.

Chondroitin sulfate (CS) glycosaminoglycans are biologically active sulfated polysaccharides that pose an analytical challenge for their structural analysis and functional evaluation. In this study, we developed a hydrophilic interaction liquid chromatography separation method and its on-line coupling to mass spectrometry (MS) allowing efficient differentiation and sensitive detection of mono-, di-, and trisulfated CS disaccharides and their positional isomers, without requiring prior derivatization. The composition of the mobile phase in terms of pH and concentration showed great influence on the chromatographic separation and was varied to allow the distinction of each CS without signal overlap for a total analysis time of 25 min.

Reactive Desorption Electrospray Ionization Mass Spectrometry To Determine Intrinsic Degradability of Poly(lactic--glycolic acid) Chains.

Because of its speed, sensitivity, and ability to scrutinize individual species, mass spectrometry (MS) has become an essential tool in analytical strategies aimed at studying the degradation behavior of polyesters. MS analyses can be performed prior to the degradation event for structural characterization of initial substrates or after it has occurred to measure the decreasing size of products as a function of time. Here, we show that MS can also be usefully employed during the degradation process by online monitoring the chain solvolysis induced by reactive desorption electrospray ionization (DESI).

Helically shaped cation receptor: design, synthesis, characterisation and first application to ion transport.

The methyl ester of 8-oxo-8-indeno[2',1':7,8]naphtho[1,2-]thiophene-2-carboxylic acid (1) and its corresponding PEGylated ester were synthesised and fully characterised. X-ray diffraction studies on (1) confirmed the helical structure of the receptor and that it is self-assembled into layers by π-π interactions. An in-depth study by DFT calculations and MS experiments (ESI-MS, MS/MS, IMRPD and ESI-IMS-MS) was carried out between (1) and the physiological cation K.

Kinetic study of azobenzene E/Z isomerization using ion mobility-mass spectrometry and liquid chromatography-UV detection.

Z and E azobenzene isomers are molecular switches which can interconvert both photochemically and thermally. Presently, we studied a ketal-substituted bridged azobenzene in which two stable diastereomeric conformers (Z1 and Z2) photochemically interconvert through the transient E isomer. UV-VIS absorption spectroscopy is commonly used to study the relaxation kinetics of azobenzenes, but it does not allow direct quantitation of the process in this case.

Stereoselective Syntheses, Structures, and Properties of Extremely Distorted Chiral Nanographenes Embedding Hextuple Helicenes.

We report a molecular design and concept using π-system elongation and steric effects from helicenes surrounding a triphenylene core toward stable chiral polycyclic aromatic hydrocarbons (PAHs) with a maximal π-distortion to tackle their aromaticity, supramolecular and molecular properties. The selective syntheses, and the structural, conformational and chiroptical properties of two diastereomeric large multi-helicenes of formula C H having a triphenylene core and embedding three [5]helicene units on their inner edges and three [7]helicene units at their periphery are reported based on diastereoselective and, when applicable, enantiospecific Yamamoto-type cyclotrimerizations of racemic or enantiopure 9,10-dibromo[7]helicene. Both molecules have an extremely distorted triphenylene core, and one of them exhibits the largest torsion angle recorded so far for a benzene ring (twist=36.

Ion mobility spectrometry - Mass spectrometry coupling for synthetic polymers.

This review covers applications of ion mobility spectrometry (IMS) hyphenated to mass spectrometry (MS) in the field of synthetic polymers. MS has become an essential technique in polymer science, but increasingly complex samples produced to provide desirable macroscopic properties of high-performance materials often require separation of species prior to their mass analysis. Similar to liquid chromatography, the IMS dimension introduces shape selectivity but enables separation at a much faster rate (milliseconds vs minutes).

Abiotic Sequence-Coded Oligomers as Efficient In Vivo Taggants for the Identification of Implanted Materials.

Sequence-defined oligourethanes were tested as in vivo taggants for implant identification. The oligomers were prepared in an orthogonal solid-phase iterative approach and thus contained a coded monomer sequence that can be unequivocally identified by tandem mass spectrometry (MS/MS). The oligomers were then included in small amounts (1 wt %) in square-centimeter-sized crosslinked poly(vinyl alcohol) (PVA) model films, which were intramuscularly and subcutaneously implanted in the abdomen of rats.

Cleavable Binary Dyads: Simplifying Data Extraction and Increasing Storage Density in Digital Polymers.

Digital polymers are uniform macromolecules that store monomer-based binary sequences. Molecularly stored information is usually extracted from the polymer by a tandem mass spectrometry (MS/MS) measurement, in which the coded chains are fragmented to reveal each bit (i.e.

Topology and Electronic Density Driven Generation of Alkali Cation Complexes.

The formation and characterization of K and Cs complexes originating from the cooperativity of three non-covalent interactions is explored. The tridimensional preorganization of the naphthothiophene platform displays a favorable well-defined bay region combining a π fragment and a carbonyl moiety flanking a central sulfur atom. A joint theoretical and experimental infrared multiple photon dissociation (IRMPD) study allowed deciphering the key contribution of the orthogonal phenyl fragment to the elaboration of alkali metal complexes.

Photocontrolled Synthesis of Abiotic Sequence-Defined Oligo(Phosphodiester)s.

A photoregulated phosphoramidite iterative process is studied for the synthesis of non-natural, digitally encoded oligo(phosphodiester)s. The oligomers are prepared using two reactive phosphoramidite monomers containing a 2-(2-nitrophenyl)propoxycarbonyl (NPPOC) protected OH group. The stepwise synthesis is performed on an OH-functional soluble polystyrene support, which allows recycling by precipitation in a nonsolvent.

Isomer separation and effect of the degree of polymerization on the gas-phase structure of chondroitin sulfate oligosaccharides analyzed by ion mobility and tandem mass spectrometry.

Rationale: Chondroitin sulfate (CS) glycosaminoglycans are bioactive sulfated polysaccharides comprising repeating units of uronic acid and N-acetyl galactose sulfated at various positions. The optimal length and sulfation pattern of the CS bioactive sequences remain elusive so that structure-activity relationships cannot be easily established. Development of efficient analytical methods allowing the differentiation of the various sulfation patterns of CS sequences is therefore of particular importance to correlate their biological functions to the sulfation pattern.

A Simple Post-Polymerization Modification Method for Controlling Side-Chain Information in Digital Polymers.

A three-step post-polymerization modification method was developed for the design of digitally encoded poly(phosphodiester)s with controllable side groups. Sequence-defined precursors were synthesized, either manually on polystyrene resins or automatically on controlled pore glass supports, using two phosphoramidite monomers containing either terminal alkynes or triisopropylsilyl (TIPS) protected alkyne side groups. Afterwards, these polymers were modified by stepwise copper-catalyzed azide-alkyne cycloaddition (CuAAC).

Identification of acylation products in SHAPE chemistry.

SHAPE chemistry (selective 2'-hydroxyl acylation analyzed by primer extension) has been developed to specifically target flexible nucleotides (often unpaired nucleotides) independently to their purine or pyrimidine nature for RNA secondary structure determination. However, to the best of our knowledge, the structure of 2'-O-acylation products has never been confirmed by NMR or X-ray data. We have realized the acylation reactions between cNMP and NMIA under SHAPE chemistry conditions and identified the acylation products using standard NMR spectroscopy and LC-MS/MS experiments.

Conformational Dynamics in Ion Mobility Data.

The shape of the spectral features in arrival time distributions (ATDs) recorded by ion mobility spectrometry (IMS) can often be interpreted in terms of the coexistence of different isomeric species. Interconversion between such species is also acknowledged to influence the shape of the ATD, even if no general quantitative description of this effect is available. We present an analytical model that allows simulating ATDs resulting from interconverting species.

Identification and separation of saxitoxins using hydrophilic interaction liquid chromatography coupled to traveling wave ion mobility-mass spectrometry.

The aim of this work was to develop a reliable and efficient analytical method to characterise and differentiate saxitoxin analogues (STX), including sulphated (gonyautoxins, GTX) and non-sulphated analogues. For this purpose, hydrophilic interaction liquid chromatography (HILIC) was used to separate sulphated analogues. We also resorted to ion mobility spectrometry to differentiate the STX analogues because this technique adds a new dimension of separation based on ion gas phase conformation.