A Photoredox Thiol-yne Reaction for the Synthesis of Vinyl Sulfide-Based Coumarins and its Effect on Fluorescence Properties.

Coumarins still remain one of the most widely explored fluorescent dyes, with a broad spectrum of applications spanning various fields, such as molecular imaging, bioorganic chemistry, materials chemistry, or medical sciences. Their fluorescence is strongly based on a push-pull mechanism involving an electron-donating group (EDG), mainly located at the C7 or C8 positions of the dye core. Unfortunately, up to now, these positions have been very limited to hydroxyl or amino groups. In this study, we present in detail the synthesis of the first series of coumarins bearing a vinyl sulfide as the EDG at the C7 position. These derivatives were prepared by thiol-yne reaction, promoted by ruthenium- or porphyrin-based photoredox catalysis, enabling rapid late-stage diversification. We also functionalized coumarins with short peptides, and BSA protein as a proof-of-concept study, in a single-step process. This strategy, capable of proceeding under aqueous conditions, overcomes the protection/deprotection steps usually required by traditional methods, which also use strong bases and organic solvents. Moreover, the photophysical properties such as absorption and emission of obtained coumarins (for 3-CF3, 3-benzothiazole, 6-8-difluoro derivatives), predominantly exhibited large Stokes shifts (up to 204 nm) and maintained intramolecular charge transfer (ICT) characteristics.

Light-Induced Unlocking Reactivity of Fragments for Fast Target-Guided Synthesis of Carbonic Anhydrase Inhibitors.

We showcase the successful combination of photochemistry and kinetic target-guided synthesis (KTGS) for rapidly pinpointing enzyme inhibitors. KTGS is a fragment-based drug discovery (FBDD) methodology in which the biological target (BT) orchestrates the construction of its own ligand from fragments featuring complementary reactive functionalities. Notably, fragments interacting with the protein binding sites leverage their spatial proximity, facilitating a preferential reaction. Consequently, the resulting bivalent ligand exhibits heightened affinity. Within the realm of KTGS strategies, in situ click chemistry stands out as the most widely used to identify potent protein binders. This approach requires significant protein contributions, such as binding interactions and appropriate orientations of fragments, to overcome high activation barriers. This leads to prolonged incubation times and the potential for generating false negatives, thereby limiting this strategy to proteins that are stable enough in buffer. We herein unveil the possibility to integrate photochemistry into the realm of KTGS, accelerating the ligation reaction between fragments to a time scale of minutes. This approach should significantly expand the narrow reactivity window of traditional KTGS reactions, paving the way for the exploration and development of novel photo-KTGS reactions.

GC-FTICR mass spectrometry with dopant assisted atmospheric pressure photoionization: application to the characterization of plastic pyrolysis oil.

Pyrolysis is a promising way to convert plastic waste into valuable resources. However, for downstream upgrading processes, many undesirable species, such as conjugated diolefins or heteroatom-containing compounds, can be generated during this pyrolysis. In-depth chemical characterization is therefore required to improve conversion and valorization. Because of the high molecular diversity found in these samples, advanced analytical instrumentation is needed to provide accurate and complete characterization. Generally, direct infusion Fourier transform mass spectrometry is used to gather information at the molecular level, but it has the disadvantage of limited structural insights. To overcome this drawback, gas chromatography has been coupled to Fourier transform ion cyclotron resonance mass spectrometry. By taking advantage of soft atmospheric pressure photoionization, which preserves molecular information, and the use of different dopants (pyrrole, toluene, and benzene), selective ionization of different chemical families was achieved. Differences in the ionization energy of the dopants will only allow the ionization of the molecules of the pyrolysis oil which have lower ionization energy, or which are accessible via specific chemical ionization pathways. With a selective focus on hydrocarbon species and especially hydrocarbon species having a double bond equivalent (DBE) value of 2, pyrrole is prone to better ionize low-mass molecules with lower retention times compared to the dopant benzene, which allowed better ionization of high-mass molecules with higher retention times. The toluene dopant presented the advantage of ionizing both low and high mass molecules.

Advances in Ultra-High-Resolution Mass Spectrometry for Pharmaceutical Analysis.

Pharmaceutical analysis refers to an area of analytical chemistry that deals with active compounds either by themselves (drug substance) or when formulated with excipients (drug product). In a less simplistic way, it can be defined as a complex science involving various disciplines, e.g., drug development, pharmacokinetics, drug metabolism, tissue distribution studies, and environmental contamination analyses. As such, the pharmaceutical analysis covers drug development to its impact on health and the environment. Moreover, due to the need for safe and effective medications, the pharmaceutical industry is one of the most heavily regulated sectors of the global economy. For this reason, powerful analytical instrumentation and efficient methods are required. In the last decades, mass spectrometry has been increasingly used in pharmaceutical analysis both for research aims and routine quality controls. Among different instrumental setups, ultra-high-resolution mass spectrometry with Fourier transform instruments, i.e., Fourier transform ion cyclotron resonance (FTICR) and Orbitrap, gives access to valuable molecular information for pharmaceutical analysis. In fact, thanks to their high resolving power, mass accuracy, and dynamic range, reliable molecular formula assignments or trace analysis in complex mixtures can be obtained. This review summarizes the principles of the two main types of Fourier transform mass spectrometers, and it highlights applications, developments, and future perspectives in pharmaceutical analysis.

Structural analysis of petroporphyrins from asphaltene by trapped ion mobility coupled with Fourier transform ion cyclotron resonance mass spectrometry.

Molecular characterization of compounds present in highly complex mixtures such as petroleum is proving to be one of the main analytical challenges. Heavy fractions, such as asphaltenes, exhibit immense molecular and isomeric complexity. Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) with its unequalled resolving power, mass accuracy and dynamic range can address the isobaric complexity. Nevertheless, isomers remain largely inaccessible. Therefore, another dimension of separation is required. Recently, ion mobility mass spectrometry has revealed great potential for isomer description. In this study, the combination of trapped ion mobility and Fourier transform ion cyclotron resonance mass spectrometry (TIMS-FTICR) is used to obtain information on the structural features and isomeric diversity of vanadium petroporphyrins present in heavy petroleum fractions. The ion mobility spectra provided information on the isomeric diversity of the different classes of porphyrins. The determination of the collision cross section (CCS) from the peak apex allows us to hypothesize about the structural aspects of the petroleum molecules. In addition, the ion mobility signal full width at half maximum (FWHM) was used as a measure for isomeric diversity. Finally, theoretical CCS determinations were conducted first on core structures and then on alkylated petroporphyrins taking advantage of the linear correlation between the CCS and the alkylation level. This allowed the proposal of putative structures in agreement with the experimental results. The authors believe that the presented workflow will be useful for the structural prediction of real unknowns in highly complex mixtures.

Regio- and Stereo-Specific Chemical Depolymerization of High Molecular Weight Polybutadiene and Polyisoprene for Their Analysis by High-Resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry: Comparison with Pyrolysis-Comprehensive Two-Dimensional Gas Chromatography/Mass Spectrometry, Atmospheric Solid Analysis Probe, Direct Inlet Probe-Atmospheric Pressure Chemical Ionization Mass Spectrometry, and Ion Mobility Spectrometry-Mass Spectrometry.

Polybutadiene (PB) and polyisoprene (PI), the two most common polydienes (PD), are involved in a large number of materials and used in a wide variety of applications. The characterization of these polymers by mass spectrometry (MS) continues to be very challenging due to their high insolubility and the difficulty to ionize them. In this work, a cross-metathesis reaction was used to generate end-functionalized acetoxy ionizable oligomers for the structural deciphering of different commercial PB and PI samples. A cross-metathesis reaction was carried out between polymers and the Z-1,4-diacetoxy-2-butene as a chain transfer agent in dichloromethane using a Hoveyda-Grubbs second-generation catalyst. Well-defined acetoxy telechelic structures were obtained and analyzed by Fourier transform ion cyclotron resonance (FTICR) high-resolution MS. However, after depolymerization, low molar mass polyolefins contained some units with different configurations, suggesting an olefin isomerization reaction due to the decomposition of the catalyst. The addition of an electron-deficient reagent such as 2,6-dichloro-1,4-benzoquinone suppressed this isomerization in the case of both Z- and E-PB and PI. Ion mobility spectrometry-mass spectrometry (IMS-MS) and energy-resolved tandem mass spectrometry (ERMS) analyses confirmed a successful isomerization suppression. For comparing the results obtained by depolymerization with classical methods for polymer analysis, pyrolysis-comprehensive two-dimensional gas chromatography/mass spectrometry (Py-GC × GC-MS), atmospheric solid analysis probe (ASAP), and direct inlet probe-atmospheric pressure chemical ionization (DIP-APCI) analyses were performed on the same polymers. This strategy can be applied on a variety of synthetic and natural not yet characterized polymers.

Paraffin-Inert Atmospheric Solid Analysis Probe: A Fast and Easy Approach To Characterize Extremely Air-Sensitive Organometallic Complexes by Mass Spectrometry.

Rational characterization of most organometallic compounds is hampered by their high reactivity, in particular, toward oxygen and water. Mass spectrometry experiments require physical introduction of the sample in the ionization source. So, the main challenge is to transfer air-sensitive organometallic compounds from inert atmosphere to the ionization source. In this aim, we have developed an easy technique that allows the analysis of air-sensitive compounds using the atmospheric solid analysis probe (ASAP). This method consists of a glass capillary filled with the sample (solid or liquid) and sealed by a paraffin plug to maintain the inert sample until the ionization process. It is illustrated through the structural characterization of a new highly air-sensitive dinuclear zirconium complex supported by an original switchable stilbene platform.

High-performance thin-layer chromatography with atmospheric solids analysis probe mass spectrometry for analysis of gasoline polymeric additives.

RATIONALE: The offline coupling of high-performance thin-layer chromatography (HPTLC) with atmospheric solids analysis probe mass spectrometry (ASAP-MS) was evaluated for the characterization of polymeric additives in gasoline. METHODS: A protocol was developed to optimize the ion signal. A glass capillary was moistened with deionized water, and then dipped into silica gel scratched from an HPTLC plate. The capillary tube was fixed to the ASAP holder and introduced into the ionization source for analysis by MS. Silica gel, reversed-phase C18 and cellulose stationary phases were evaluated. RESULTS: The effect of the stationary phase and the nature of analyte were evaluated using polypropylene glycol and polyisobutylene succinimide polyamine as analyte molecules. The optimal ionization conditions are significantly different between ASAP and HPTLC/ASAP-MS analyses. In particular, a higher desorption gas temperature was required to produce ions from the silica gel HPTLC plate. The presence of the stationary phase reduces the internal energy of the ions and limits the fragmentation. CONCLUSIONS: HPTLC/ASAP-MS is a very fast and efficient technique for the analysis of polymers in formulated fuels. Good ionization efficiency was obtained with all investigated stationary phases.

Diverted Natural Lossen-type Rearrangement for Bioconjugation through in Situ Myrosinase-Triggered Isothiocyanate Synthesis.

Fluorescein isothiocyanate (FITC) is one of the most extensively used fluorescent probes for the labeling of biomolecules. The isothiocyanate function reacts with lysine residues of proteins to provide a chemically stable thiourea linkage without releasing any byproduct. However, diversification of isothiocyanate-based reagents is still hampered by the lack of mild conditions to generate isothiocyanate chemical functions, as well as by their poor stability and limited solutions available to increase water solubility, restricting the use of isothiocyanate labeling to highly water-soluble fluorophores. Inspired by plant biological processes, we report a safe and biocompatible myrosinase-assisted in situ formation of isothiocyanate conjugates from a highly water-soluble and stable glucosinolate precursor. This method was applied for the fluorescence labeling of a plasmatic protein and fluorescence imaging of living cells.

Structural analysis of heavy oil fractions after hydrodenitrogenation by high-resolution tandem mass spectrometry and ion mobility spectrometry.

Heavy petroleum fractions such as vacuum gas oils (VGOs) are structurally and compositionally highly complex mixtures. Nitrogen species, which have a significant impact on the subsequent refining processes, are generally removed by the hydrodenitrogenation (HDN) catalytic process. The purpose of this study was to identify and characterize compounds that are refractory to the HDN process. This may allow for the examination of the effectiveness of a vacuum distillate hydrotreatment catalytic bed in removing nitrogen-containing compounds before the cracking step. Three different VGO fractions of the same oil before and after HDN processes were analysed in ESI(+) mode by FTICR mass spectrometry and ion mobility spectrometry-mass spectrometry (IMS-MS), in particular compounds containing basic nitrogen, such as quinoline and isoquinoline. Ultra-high-resolution FTICR mass spectrometry provides a sufficiently high mass resolution power to resolve different compounds and attribute a unique molecular formula to each ion. Information on the isomeric content was obtained by use of tandem mass spectrometry (MS/MS) and IMS-MS. The evolution of the fragmentation of the N1 class of compounds as a function of collision energy allowed for the identification of the molecular nucleus raw formula. From the IMS-MS experiments, it clearly appeared that, based on the IMS peak width, a lower isomeric dispersity was obtained after the HDN process and, based on the drift time and collision cross section determination, species presenting longer alkyl branches are the molecules most refractory to the HDN process.

A Unique (3+2) Annulation Reaction between Meldrum's Acid and Nitrones: Mechanistic Insight by ESI-IMS-MS and DFT Studies.

The fragile intermediates of the domino process leading to an isoxazolidin-5-one, triggered by unique reactivity between Meldrum's acid and an N-benzyl nitrone in the presence of a Brønsted base, were determined thanks to the softness and accuracy of electrospray ionization mass spectrometry coupled to ion mobility spectrometry (ESI-IMS-MS). The combined DFT study shed light on the overall organocatalytic sequence that starts with a stepwise (3+2) annulation reaction that is followed by a decarboxylative protonation sequence encompassing a stereoselective pathway issue.

Characterization of polyalphaolefins using halogen anion attachment in atmospheric pressure photoionization coupled with ion mobility spectrometry-mass spectrometry.

Polyalphaolefins (PAOs) are saturated alpha olefin oligomers used as a base stock oil for synthetic lubricants. The synthetic base stocks are manufactured from linear alpha olefins by catalytic oligomerization processes. The aim of this work was the characterization of different PAO grades, synthesized from different linear alpha olefins using two oligomerization processes, acid and metallocene catalyses. Negative ion atmospheric pressure photoionization (APPI) coupled with ion mobility spectrometry-mass spectrometry (IMS-MS) permitted the detection of intact PAO adducts with either chloride, bromide or iodide ions using halogenated solvents (e.g. dichloromethane, dibromomethane and diiodomethane) and toluene as the dopant. The best signal-to-noise ratio was obtained with dichloromethane. The APPI mass spectra displayed characteristic ion distributions for high viscosity PAO grades. The mass shift between two adjacent ions permitted the identification of repeating units and consequently the monomers of alpha olefins used to manufacture the PAO. For low PAO grades, the halide anion adducts were not detected as they are less stable. The IMS-MS data, as well as the correlated variables, i.e. the drift time and full width at half maximum (FWHM) of the IMS peaks, can be used to differentiate polyalphaolefins of the same grade but differently synthesized.

Synthesis and Unprecedented Complexation Properties of ß-Cyclodextrin-Based Ligand for Lanthanide Ions.

Here, we report the synthesis and detailed studies on the coordination chemistry of a novel chemically modified polyaminocarboxylate (5) based on ß-cyclodextrin (CD) scaffold for lanthanides. The target ligand is prepared in a highly efficient manner (seven total steps) from ß-CD using the readily available iminodiacetic acid as a starting material. A propargyl group is attached to the iminodiacetate via N-alkylation, and the obtained derivative is efficiently conjugated to the ß-CD scaffold via the copper(I)-mediated 1,3-dipolar cycloaddition. The generated 1,2,3-triazolmethyl residues advantageously provide a competent chelating group while displacing the metal coordination center away from the primary rim of ß-CD, to afford the required conformational flexibility. The functional groups from each of the two adjacent glucopyranosyl units of ß-CD complete a uniquely created octavalent coordination sphere for lanthanides while still sparing one site for dynamic water coordination. To help study the coordination chemistry of CD ligand 5, we also design a relevant maltoside ligand 6, which faithfully represents one submetal-binding section of ligand 5. Thanks to HRMS and NMR studies, we successfully elucidate the coordination chemistries of synthesized ligands. The octavalent coordination sphere of ligand 5 shows strong binding affinity to lanthanides. By potentiometric titration experiments, ligand 5 is found to bind gadolinium(III), forming 1:1, 1:2, and 1:3 multinuclear complexes with lanthanides, thus possessing great capacity for catalyzing the dynamic water-exchange. Further NMR studies also reveal that the formed ligand 5/Gd(III) complexes show significantly better abilities to alter T1 relaxivities of coordinated water than DOTA-Gd(III) and also some of the synthetic CD probes reported in the literature.

Readily functionalizable phosphonium-tagged fluorescent coumarins for enhanced detection of conjugates by mass spectrometry.

Fluorescent coumarins are an important class of small-molecule organic fluorophores ubiquitous in different well-established and emerging fields of research including, among others, biochemistry and chemical biology. The present work aims at covering the poor detectability of coumarin-based conjugates by mass spectrometry while keeping important photophysical properties of the coumarin core. In this context, the synthesis of readily functionalizable phosphonium-tagged coumarin derivatives enabling a dual mass-tag and fluorescence labelling of analytes or (bio)molecules of interest through a single-step protocol, is reported. The utility of these coumarins is illustrated through the preparation of fluorogenic substrates that facilitated identification of the peptide fragment released by specific proteolytic cleavages.

Determination of Multimodal Isotopic Distributions: The Case of a (15)N Labeled Protein Produced into Hairy Roots.

Isotopic labeling is widely used in various fields like proteomics, metabolomics, fluxomics, as well as in NMR structural studies, but it requires an efficient determination of the isotopic enrichment. Mass spectrometry is the method of choice for such analysis. However, when complex expression systems like hairy roots are used for production, multiple populations of labeled proteins may be obtained. If the isotopic incorporation determination is actually well-known for unimodal distributions, the multimodal distributions have scarcely been investigated. Actually, only a few approaches allow the determination of the different labeled population proportions from multimodal distributions. Furthermore, they cannot be used when the number of the populations and their respective isotope ratios are unknown. The present study implements a new strategy to measure the (15)N labeled populations inside a multimodal distribution knowing only the peptide sequence and peak intensities from mass spectrometry analyses. Noteworthy, it could be applied to other elements, like carbon and hydrogen, and extended to a larger range of biomolecules.

Atmospheric Solid Analysis Probe-Ion Mobility Mass Spectrometry: An Original Approach to Characterize Grafting on Cyclic Olefin Copolymer Surfaces.

A cyclic olefin copolymer (COC) was grafted with aryl layers from aryldiazonium salts, and then we combined infrared spectrometry, atomic force microscopy (AFM), and ion mobility mass spectrometry with atmospheric solid analysis probe ionization (ASAP-IM-MS) to characterize the aryl layers. ASAP is a recent atmospheric ionization method dedicated to the direct analysis of solid samples. We demonstrated that ASAP-IM-MS is complementary to other techniques for characterizing bromine and sulfur derivatives of COC on surfaces. ASAP-IM-MS was useful for optimizing experimental grafting conditions and to elucidate hypotheses around aryl layer formation during the grafting process. Thus, ASAP-IM-MS is a good candidate tool to characterize covalent grafting on COC surfaces.

Exploration of polyamide structure-property relationships by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

RATIONALE: Polyamides (PA) are among the most used classes of polymers because of their attractive properties. Depending on the nature and proportion of the co-monomers used for their synthesis, they can exhibit a very large range of melting temperatures (Tm ). This study aims at the correlation of data from mass spectrometry (MS) with differential scanning calorimetry (DSC) and X-ray diffraction analyses to relate molecular structure to physical properties such as melting temperature, enthalpy change and crystallinity rate. METHODS: Six different PA copolymers with molecular weights around 3500 g mol(-1) were synthesized with varying proportions of different co-monomers (amino-acid AB/di-amine AA/di-acid BB). Their melting temperature, enthalpy change and crystallinity rate were measured by DSC and X-ray diffraction. Their structural characterization was carried out by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Because of the poor solubility of PA, a solvent-free sample preparation strategy was used with 2,5-dihydroxybenzoic acid (2,5-DHB) as the matrix and sodium iodide as the cationizing agent. RESULTS: The different proportions of the repeating unit types led to the formation of PA with melting temperatures ranging from 115°C to 185°C. The structural characterization of these samples by MALDI-TOF-MS revealed a collection of different ion distributions with different sequences of repeating units (AA, BB; AB/AA, BB and AB) in different proportions according to the mixture of monomers used in the synthesis. The relative intensities of these ion distributions were related to sample complexity and structure. They were correlated to DSC and X-ray results, to explain the observed physical properties. CONCLUSIONS: The structural information obtained by MALDI-TOF-MS provided a better understanding of the variation of the PA melting temperature and established a structure-properties relationship. This work will allow future PA designs to be monitored.

Investigation of dendriplexes by ion mobility-mass spectrometry.

Highly branched polyamidoamine (PAMAM) dendrimers presenting biological activities have been envisaged as non-viral gene delivery vectors. They are known to associate with nucleic acid (DNA) in non-covalent complexes via electrostatic interactions. Although their transfection efficiency has been proved, PAMAMs present a significant cytotoxicity due to their cationic surface. To overcome such a drawback, different chemical modifications of the PAMAM surface have been reported such as the attachment of hydrophobic residues. In the present work, we studied the complexation of DNA duplexes with different low-generation PAMAM; ammonia-cored G0(N) and G1(N) PAMAM, native or chemically modified with aromatic residues, i.e., phenyl-modified-PAMAM G0(N) and phenylalanine-modified-PAMAM G1(N). To investigate the interactions involved in the PAMAM/DNA complexes, also called dendriplexes, we used electrospray ionization (ESI) coupled to ion mobility spectrometry-mass-spectrometry (IM-MS). ESI is known to allow the study of non-covalent complexes in native conditions while IM-MS is a bidimensional separation technique particularly useful for the characterization of complex mixtures. IM-MS allows the separation of the expected complexes, possible additional non-specific complexes and the free ligands. Tandem mass spectrometry (MS/MS) was also used for the structural characterization. This work highlights the contribution of IM-MS and MS/MS for the study of small dendriplexes. The stoichiometries of the complexes and the equilibrium dissociation constants were determined. The [DNA/native PAMAM] and [DNA/modified-PAMAM] dendriplexes were compared.

Contribution of LDI and MALDI for the Characterization of a Lignocellulosic-Based Pyrolysis Bio-Oil.

In recent years, various alternatives to fossil fuels have been developed. One of them involves the production of bio-oils from lignocellulosic-based biomass through pyrolysis. However, bio-oils present numerous heteroatoms and, in particular, oxygen atoms that need to be removed by an upgrading process. To optimize these processes, it is necessary to have good knowledge of the composition of the bio-oils at the molecular level. This work aims to establish the usefulness of laser desorption ionization (LDI) and matrix-assisted laser desorption/ionization (MALDI) techniques on lignocellulosic biomass-based bio-oils. Using a Fourier transform ion cyclotron mass spectrometer (FTICR MS), we showed that MALDI gives more information than LDI. The selectivity of a series of MALDI matrices was investigated, showing that some matrices are selective toward compound families and others ionize a wider range of compounds. In this study, nine proton-transfer matrices and three electron-transfer matrices were used and compared to results obtained in LDI. Dithranol, acetosyringone, and graphene oxide were the three promising matrices selected from all matrices, giving an overall characterization of oxygenated classes in a bio-oil. They allowed the ionization of many more species covering a wide range of polarity, aromaticity, and mass with a homogeneous relative intensity for all molecular classes such as lignin-derivative species, sugars, and lipid-derivative species.

Mechanistic study of maleic anhydride grafting onto fatty double bonds using mass spectrometry.

RATIONALE: The grafting of maleic anhydride onto fatty C=C double bonds is a well-known and used method to functionalize triglyceride molecules. Nevertheless, grafted products are not actually structurally well defined. In this work, the thermal grafting of maleic anhydride onto (un)saturated fatty acid esters without the use of an initiator was characterized in order to determine the nature of the products formed during this reaction. METHODS: Complementary spectrometric techniques, ESI-MS(n) (ion-trap mass spectrometer), IMS-MS(n) (Q-IMS-TOFMS) and GC/MS, were used to identify the grafted products which were prepared using either ethyl oleate (EtO) or methyl linoleate (MeL) as model molecules and maleic anhydride (MA). Lithiated adducts were investigated since they yield useful structural information when subjected to collision-induced dissociation (CID) in tandem mass spectrometry. RESULTS: A high number of products are formed during MA grafting and various reaction types could occur. Radical addition of maleic anhydride followed by combination or elimination reactions led to succinic and maleic anhydride grafting, respectively. The addition occurred with or without double-bond shift; the resulting derivatives showed succinic and maleic anhydride branching in the α-position relative to the double bond or onto the carbon atom of the initial double bond. Some structures obtained by radical addition and combination were also consistent with the Alder ene functionalization reaction. The Diels-Alder addition between di-unsaturated fatty acid chains and maleic anhydride could yield cyclic forms of MA-grafted derivatives. CONCLUSIONS: We have shown that ESI-MS(n) and IMS-MS(n) allow the identification of grafted products providing relevant structural information concerning isomers. These methods permit the rapid and direct analyses of 'crude reaction mixtures'.