Mass Spectrometric determination of the Electronaffinities of Radicals.

in Chemical Physics Letters (1970), 6(4), 273-276

By mass spectrometric study of the appearance of C2-, CH- and C2H- from CH4, C2H2, C2H4, C2H3X (X=F, Cl) the following electronaffinities have been determined: EA(CH)=(2.6+/-0.3) eV, EA(C2)=(3.3+/-0.2) eV ... [more ▼]

By mass spectrometric study of the appearance of C2-, CH- and C2H- from CH4, C2H2, C2H4, C2H3X (X=F, Cl) the following electronaffinities have been determined: EA(CH)=(2.6+/-0.3) eV, EA(C2)=(3.3+/-0.2) eV and EA(C2H)=(2.1+/-0.3) eV. Some evidence is brought to the existence of electronic excited states of these ions. An evaluation of these negative ions dissociation energy in their ground electronic state is given and is found to be of the order of magnitude of the corresponding isoelectronic molecular species dissociation energy. [less ▲]

Mass spectrometric sequencing of peptidic toxins : an overview

in Editions de la SFET – SFET Editions (2010)

Mass Spectrometric Study of Dissociative Attachment in Diatomic Molecules:I. CO and H2

in International Journal of Mass Spectrometry and Ion Physics (1969), 2

A study of the shape of the DA peaks leads to a general method for the determination of the threshold of a DA process. In order to test this method, the negative ions appearing in CO and H2 have been ... [more ▼]

A study of the shape of the DA peaks leads to a general method for the determination of the threshold of a DA process. In order to test this method, the negative ions appearing in CO and H2 have been investigated, using a sector field instrument. An attempt has been made to establish the relative positions of the potential energy curves (using the Morse function) for the electronic states involved in the processes observed [less ▲]

Mass Spectrometric Study of Ion-Pair Processes in Diatomic Molecules: H2, CO, NO and O2.

in International Journal of Mass Spectrometry and Ion Physics (1971), 7

The appearance of ion-pair processes has been studied in H2, CO, NO and O2. The different thresholds have been interpreted. Convolution and deconvolution techniques have been applied to the ionization ... [more ▼]

The appearance of ion-pair processes has been studied in H2, CO, NO and O2. The different thresholds have been interpreted. Convolution and deconvolution techniques have been applied to the ionization efficiency curves to determine (i) a method for the determination of the threshold energy and (ii) the kinetic energy distribution of the fragments. [less ▲]

Mass spectrometry and ion mobility spectrometry of G-quadruplexes. A study of solvent effects on dimer formation and structural transitions in the telomeric DNA sequence d(TAGGGTTAGGGT).

in Methods (2012), 57(1), 56-63

We survey here state of the art mass spectrometry methodologies for investigating G-quadruplexes, and will illustrate them with a new study on a simple model system: the dimeric G-quadruplex of the 12-mer ... [more ▼]

We survey here state of the art mass spectrometry methodologies for investigating G-quadruplexes, and will illustrate them with a new study on a simple model system: the dimeric G-quadruplex of the 12-mer telomeric DNA sequence d(TAGGGTTAGGGT), which can adopt either a parallel or an antiparallel structure. We will discuss the solution conditions compatible with electrospray ionisation, the quantification of complexes using ESI-MS, the interpretation of ammonium ion preservation in the complexes in the gas phase, and the use of ion mobility spectrometry to resolve ambiguities regarding the strand stoichiometry, or separate and characterise different structural isomers. We also describe that adding electrospray-compatible organic co-solvents (methanol, ethanol, isopropanol or acetonitrile) to aqueous ammonium acetate increases the stability and rate of formation of dimeric G-quadruplexes, and causes structural transitions to parallel structures. Structural changes were probed by circular dichroism and ion mobility spectrometry, and the excellent correlation between the two techniques validates the use of ion mobility to investigate G-quadruplex folding. We also demonstrate that parallel G-quadruplex structures are easier to preserve in the gas phase than antiparallel structures. [less ▲]

Mass spectrometry as an evolutive tool for toxinology: from sequencing to toxin shapes

Conference (2011, September 12)

Mass spectrometry imaging of rat brain sections: nanomolar sensitivity with MALDI versus nanometer resolution by TOF–SIMS

in Analytical and Bioanalytical Chemistry (2010), 396(1), 151-162

Mass spectrometry imaging is becoming a more and more widely used method for chemical mapping of organic and inorganic compounds from various surfaces, especially tissue sections. Two main different ... [more ▼]

Mass spectrometry imaging is becoming a more and more widely used method for chemical mapping of organic and inorganic compounds from various surfaces, especially tissue sections. Two main different techniques are now available: matrix-assisted laser desorption/ionizaton, where the sample, preliminary coated by an organic matrix, is analyzed by a UV laser beam; and secondary ion mass spectrometry, for which the target is directly submitted to a focused ion beam. Both techniques revealed excellent performances for lipid mapping of tissue surfaces. This article will discuss similarities, differences, and specificities of ion images generated by these two techniques in terms of sample preparation, sensitivity, ultimate spatial resolution, and structural analysis. [less ▲]

Mass spectrometry of G-quadruplexes

Conference (2010, May 31)

Mass transfer in low-density xerogel catalysts

in AIChE Journal (2001), 47(8), 1866-1873

Texture and morphology of a Pd-Ag/SiO2 hydrodechlorination low-density xerogel catalyst prepared by a cogelation sot-gel process were characterized in detail to examine mass transfer in such catalysts ... [more ▼]

Texture and morphology of a Pd-Ag/SiO2 hydrodechlorination low-density xerogel catalyst prepared by a cogelation sot-gel process were characterized in detail to examine mass transfer in such catalysts. The catalyst consists of active Pd-Ag nanocrystallites trapped inside elementary 20 nm microporous silica particles arranged in larger aggregates, which constitute the macroscopic pellet. To reach active sites, reactants must first diffuse through large pores located between aggregates of SiO2 Particles and then through smaller pores located between those elementary particles inside the aggregates. Finally, they, diffuse through micropores located inside silica particles. Diffusion in such a "funnel" structure cannot be described assimilating the pellet to a pseudo-continuum. Diffusion should be examined carefully at three levels of decreasing size: the macroscopic pellet, the aggregate of silica particles, and the elementary silica particle. This approach shows that cogelled xerogel catalysts have remarkable mass-transfer properties. [less ▲]

Mass transport in carbon gels with tuned porosity

in Spanish Carbon Group Bulletin (2012)