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The analysis of pterins in the cerebrospinal fluid (CSF) is mandatory for the etiologic diagnosis of inborn errors of dopamine and serotonin metabolism. The success of the available therapeutic strategies for preventing the ongoing brain dysfunction is tightly dependent of the early diagnosis of these neurotransmitter disorders. Previous methods of pterins determination in the CSF have in common at least one reversed phase HPLC step coupled to electrochemical or fluorescence detection (FD). They differ in the oxidation procedure of the reduced forms of pterins into their oxidized fluorescent counterparts. Most of the methods using the FD include at least one offline chemical oxidation procedure and cannot allow the direct quantification of tetrahydrobiopterin (BH4). A recent method proposed a single step simultaneous quantification of all forms of pterins including BH4 by HPLC coupled to FD after post-column coulometric oxidation. Nowadays, recent advances in mass spectrometry (MS), notably in term of sensitivity, allow the direct unambiguous determination of all forms of pterins in the CSF by LC-MS/MS.

Curcumin (Cur) is a natural polyphenol with a wide spectrum of biological activities and appealing therapeutic potential. Herein, it has been delivered by electrospray ionization as gaseous protonated species, [Cur + H]+, and as a Cu(ii) complex, [Cu(Cur − H)]+, a promising antioxidant and radical scavenger. The gas phase structures were assayed by infrared multiple photon dissociation (IRMPD) spectroscopy in both the fingerprint (800–2000 cm−1) and hydrogen stretching (3100–3750 cm−1) ranges. Comparison between the experimental features and linear IR spectra of the lowest energy structures computed at the B3LYP/6-311+G(d,p) level reveals that bare [Cu(Cur − H)]+ exists in a fully planar and symmetric arrangement, where the metal interacts with the two oxygens of the syn-enolate functionality of deprotonated Cur and both OCH3 groups are engaged in H-bonding with the ortho OH. The effect of protonation on the energetic and geometric determinants of Cur has been explored as well, revealing that bare [Cur + H]+ may exist as a mixture of two close-lying isomers associated with the most stable binding motifs. The additional proton is bound to either the diketo or the keto-enol configuration of Cur, in a bent or nearly planar arrangement, respectively. [ABSTRACT FROM AUTHOR]

Protonated fluorobenzene ions (C(sub 6)H(sub 6)F(super +) are produced by chemical ionization of C 6H5F in the cell of a FT- ICR mass spectrometer. Comparison of the above two protonated fluorobenzene ions reveal the effects of both protonation and H---> F substitution on the structural properties of these fundamental aromatic molecules.

Infrared spectra in the mid-infrared region of highly unsaturated Fe+-hydrocarbon complexes isolated in the gas phase are presented. The infrared spectroscopy is a very powerful tool to characterize selectivity prepared molecular ions using a Fourier transform ion cycloton mass spectometer.

Electron correlated, ab-initio theoretical and density functional theory methods were used in a study on phosphinines to investigate the 24 possible valence isomers of diphosphinine P2(C-H)4. It appears that three planar isomers are distinctly more stable than others. The various families of isomers have distinct ranges of stabilities which virtually do not overlap at the MP2 level. Other experimental results and conclusions are discussed.

Research was conducted to examine the origin of bonding interactions in Cu+(H2)n clusters. The binding energies and entropies were calculated for the attachment of up to six H2 ligands to ground-state Cu+ ions to electronically excited Cu+* ions and to hydrated H2O*Cu+ ions. Results demonstrate that covalent interactions are critical in the Cu+ clusters and that the observed changes in bond dissociation energies as different ligands are added are attributable to electronic rather than steric effects.

Kinetic studies involving temperature-dependent equilibrium measurements help determine the binding energies and entropies for the insertion of Sc+ into H2 forming Sc+(H2)n (n = 1-5) clusters. Binding energy and negative temperature dependence of the formation rate suggest the insertion of Sc+ into first H2 ligand and form two covalent sigma bonds with H-atoms. Scandium ion size and steric interference of H2 ligands influence the binding energies. A mechanism involving uninserted Sc+(H2)n clusters explains the kinetic data and ab initio calculations support this mechanism involving sigma-bond activation by transition metal centers.

The multistructural valence bond computation of bonding in the sigma-bond series H-H, Li-Li, H3C-H, H3Si-H, Na-F, F-F, H3C-F, HO-OH, H2N-NH2, H-F, H3C-F and H3Si-F is performed. Large resonance energies dominate bonding in charge-shift bonds because of the mixing of the spin-paired Heitler-London structure with the ionic structures. These large ionic-covalent resonance energies and the negative deformation densities of these bond types originate from the reduced kinetic energy of the bonding electrons in the internuclear region.

The structures of proton‐bound complexes of 5,7‐dimethoxy‐4H‐chromen‐4‐one (1) and basic amino acids (AAs), namely, histidine (His) and lysine (Lys), have been examined by means of mass spectrometry coupled with IR ion spectroscopy and quantum chemical calculations. This selection of systems is based on the fact that 1 represents a portion of glabrescione B, a natural small molecule of promising antitumor activity, while His and Lys are protein residues lining the cavity of the alleged receptor binding site. These species are thus a model of the bioactive adduct, although clearly the isolated state of the present study bears little resemblance to the complex biological environment. A common feature of [1+AA+H]+ complexes is the presence of a protonated AA bound to neutral 1, in spite of the fact that the gas‐phase basicity of 1 is comparable to those of Lys and His. The carbonyl group of 1 acts as a powerful hydrogen‐bond acceptor. Within [1+AA+H]+ the side‐chain substituents (imidazole group for His and terminal amino group for Lys) present comparable basic properties to those of the α‐amino group, taking part to a cooperative hydrogen‐bond network. Structural assignment, relying on the comparative analysis of the infrared multiple photon dissociation (IRMPD) spectrum and calculated IR spectra for the candidate geometries, derives from an examination over two frequency ranges: 900–1800 and 2900–3700 cm−1. Information gained from the latter one proved especially valuable, for example, pointing to the contribution of species characterized by an unperturbed carboxylic OH or imidazole NH stretching mode. [ABSTRACT FROM AUTHOR]