Experimental and theoretical study of the gas-phase interaction between ionized nitrile sulfides and pyridine

AbstractThe gas-phase reactivity of ionized nitrile sulfides, R-CN+-S•, towards neutral pyridine was studied both experimentally (six sector hybrid mass spectrometer) and theoretically (density functional theory and Møller-Plesset ab initio calculations). An ionized sulfur atom transfer and a cycloaddition process respectively yielding ionized pyridine N-thioxide and a thiazolopyridinium cation were observed. Whereas the very efficient S•+ transfer reaction probably involves the intermediacy of several ion-molecule complexes, the thiazolopyridinium ion formation is likely to be initiated by an electrophilic attack of the R-CN+-S• ion on the nitrogen atom of pyridine; the resulting intermediate then undergo an intramolecular substitution of an α-hydrogen atom by the sulfur atom

Qualitative and quantitative study of Saponin contents of five sea cucumbers of the Indian Ocean

peer reviewedTo avoid predation, holothuroids produce feeding-deterrent molecules in their body wall and viscera, the so-called saponins. Five tropical sea cucumber species of the family Holothuriidae were investigated in order to study their saponin content in two d

Elucidation of molecular diversity and body distribution of saponins in the sea cucumber Holothuria forskali (Echinodermata) by mass spectrometry

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Chromatographic, Spectrometric and NMR Characterization of a New Set of Glucuronic Acid Esters Synthesized by Lipase

An enzymatic synthesis was developed on a new set of D-glucuronic acid esters and particularly the tetradecyl-D-glucopyranosiduronate also named tetradecyl D-glucuronate. Chromatographic analyses revealed the presence of the ester as a mixture of anomeric forms for carbon chain lengths superior to 12. TOF/MS and MS/MS studies confirmed the synthesis of glucuronic acid ester. The NMR study also confirmed the structure of glucuronic acid esters and clearly revealed an anomeric (α/β) ratio equivalent to 3/

Asteraceae paradox: Chemical and mechanical protection of taraxacum pollen

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Echinometra mathaei and its ectocommensal shrimps: the role of sea urchin spinochrome pigments in the symbiotic association

peer reviewe

Real-time monitoring of enzymatic DNA hydrolysis by electrospray ionization mass spectrometry

A fast and direct method for the monitoring of enzymatic DNA hydrolysis was developed using electrospray ionization mass spectrometry. We incorporated the use of a robotic chip-based electrospray ionization source for increased reproducibility and throughput. The mass spectrometry method allows the detection of DNA fragments and intact non-covalent protein–DNA complexes in a single experiment. We used the method to monitor in real-time single-stranded (ss) DNA hydrolysis by colicin E9 DNase and to characterize transient non-covalent E9 DNase–DNA complexes present during the hydrolysis reaction. The mass spectra showed that E9 DNase interacts with ssDNA in the absence of a divalent metal ion, but is strictly dependent on Ni(2+) or Co(2+) for ssDNA hydrolysis. We demonstrated that the sequence selectivity of E9 DNase is dependent on the ratio protein:ssDNA or the ssDNA concentration and that only 3′-hydroxy and 5′-phosphate termini are produced. It was also shown that the homologous E7 DNase is reactive with Zn(2+) as transition metal ion and that this DNase displays a different sequence selectivity. The method described is of general use to analyze the reactivity and specificity of nucleases

Gas-phase structure of polymer ions: Tying together theoretical approaches and ion mobility spectrometry.

peer reviewedAn increasing number of studies take advantage of ion mobility spectrometry (IMS) coupled to mass spectrometry (IMS-MS) to investigate the spatial structure of gaseous ions. Synthetic polymers occupy a unique place in the field of IMS-MS. Indeed, due to their intrinsic dispersity, they offer a broad range of homologous ions with different lengths. To help rationalize experimental data, various theoretical approaches have been described. First, the study of trend lines is proposed to derive physicochemical and structural parameters. However, the evaluation of data fitting reflects the overall behavior of the ions without reflecting specific information on their conformation. Atomistic simulations constitute another approach that provide accurate information about the ion shape. The overall scope of this review is dedicated to the synergy between IMS-MS and theoretical approaches, including computational chemistry, demonstrating the essential role they play to fully understand/interpret IMS-MS data

Helicity of Peptoid Ions in the Gas Phase

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