IRMPD spectroscopy and quantum chemistry calculations on mono- and bi-metallic complexes of acetylacetonate ligands with aluminum, iron, and ruthenium ions.

Metal-ligand cluster ions are structurally characterized by means of gas-phase infrared multiple photon dissociation spectroscopy. The mass-selected complexes consist of one or two metal cations M3+ (M = Al, Fe, or Ru) and two to five anionic bidentate acetylacetonate ligands. Experimental IR spectra are compared with different density functional theory calculations, namely, PBE/TZVP, B3LYP/6-31G*, and M06/6-31+G**. Frequency analysis was also performed at different levels, namely, scaled static harmonic and unscaled static anharmonic, or with ab initio molecular dynamics simulations at the PBE/TZVP level. All methods lead to simulated spectra that fit rather well with experimental data, and the spectral red shifts of several main bands, in the 1200 cm-1-1800 cm-1 range, are sensitive to the strength of the metal-ligand interaction and to the spin state of the ion. Due to the rigidity of those complexes, first principles molecular dynamics calculations provide spectra similar to that produced by static calculations that are already able to catch the main spectral signatures using harmonic calculations at the B3LYP/6-31G* level.

Tandem mass spectrometry and infrared spectroscopy as a tool to identify peptide oxidized residues.

The final products obtained by the oxidation of small model peptides containing the thioether function, either methionine or S-methyl cysteine, have been characterized by tandem mass spectrometry and IR Multiple Photon Dissociation (IRMPD) spectroscopy. The modified positions have been clearly identified by the CID-MS(2) fragmentation mass spectra with or without loss of sulfenic acid, as well as by the vibrational signature of the sulfoxide bond at around 1000 cm(-1). The oxidation of the thioether function did not lead to the same products in these model peptides. The sulfoxide and sulfone (to a lesser extent) have been clearly identified as final products of the oxidation of S-methyl-glutathione (GS-Me). Decarboxylation or hydrogen loss are the major oxidation pathways in GS-Me, while they have not been observed in tryptophan-methionine and methionine-tryptophan (Trp-Met and Met-Trp). Interestingly, tryptophan is oxidized in the dipeptide Met-Trp, while that is not the case in the reverse sequence (Trp-Met).

Conformational analysis of quinine and its pseudo enantiomer quinidine: a combined jet-cooled spectroscopy and vibrational circular dichroism study.

Laser-desorbed quinine and quinidine have been studied in the gas phase by combining supersonic expansion with laser spectroscopy, namely, laser-induced fluorescence (LIF), resonance-enhanced multiphoton ionization (REMPI), and IR-UV double resonance experiments. Density funtional theory (DFT) calculations have been done in conjunction with the experimental work. The first electronic transition of quinine and quinidine is of π-π* nature, and the studied molecules weakly fluoresce in the gas phase, in contrast to what was observed in solution (Qin, W. W.; et al. J. Phys. Chem. C2009, 113, 11790). The two pseudo enantiomers quinine and quinidine show limited differences in the gas phase; their main conformation is of open type as it is in solution. However, vibrational circular dichroism (VCD) experiments in solution show that additional conformers exist in condensed phase for quinidine, which are not observed for quinine. This difference in behavior between the two pseudo enantiomers is discussed.

Chiral recognition in cinchona alkaloid protonated dimers: mass spectrometry and UV photodissociation studies.

Chiral recognition in protonated cinchona alkaloid dimers has been studied in mass spectrometry experiments. The experimental setups involved a modified 7T FT-ICR (Fourier transform-ion cyclotron resonance) mass spectrometer (MS) and a modified Paul ion trap both equipped with an electrospray ionization source (ESI). The Paul ion trap has been coupled to a frequency-doubled dye laser. The fragmentation of protonated dimers made from cinchonidine (Cd) and the two pseudoenantiomers of quinine, namely, quinine (Qn) and quinidine (Qd), has been assessed by means of collision-induced dissociation (CID) as well as UV photodissociation (UVPD). Whereas CID fragmentation of the dimers only leads to the evaporation of the monomers, UVPD results in the additional loss of a neutral radical fragment corresponding to the quinuclidinyl radical. The effect of the excitation wavelength and of complexation with H(2)SO(4) has been studied to cast light on the reaction mechanism. Complexation with H(2)SO(4) modifies the photoreactivity of the dimers; only evaporation of the monomeric fragments, quinine, and cinchonidine is observed. Comparison between the mass spectra of the cinchona alkaloid (CdQnH(+)) or (CdQdH(+)) dimers resulting from the UVPD of (CdQnH(2)SO(4)H(+)) and that of bare (CdQnH(+)) helps propose a fragmentation mechanism, which is thought to involve fast proton transfer from the quinuclidine part of a molecular subunit to the quinoline ring. CID and UV fragmentation experiments show that the homochiral dimer is more strongly bound than the heterochiral adduct.

Structural characterization by IRMPD spectroscopy and DFT calculations of deprotonated phosphorylated amino acids in the gas phase.

Gas-phase infrared spectra of deprotonated phosphorylated amino acids ([pAA-H](-))-phosphoserine ([pSer-H](-)), phosphothreonine ([pThr-H](-)), and phosphotyrosine ([pTyr-H](-))-and of the dihydrogen phosphate anion H(2)PO(4)(-) have been recorded in the mid-IR region (650-2000 cm(-1)) under tandem mass spectrometry conditions. The experimental setup involved a Paul ion trap equipped with an electrospray ionization source coupled with a tunable free electron laser (FEL). Spectral assignment of the observed IRMPD bands and identification of the vibrational signatures of the phosphorylation have been performed by comparison with DFT calculations. The H(2)PO(4)(-) anion has been used as a simple model of a free deprotonated phosphate group, helping the identification of the IR signatures of phosphorylation. Our results show that deprotonation occurs on the phosphate group for the three amino acids. A comparison between the deprotonated and protonated phosphorylated amino acids is reported for the most important vibrational features.

Chiral discrimination of 2,3-butanediols by laser spectroscopy.

The resonance enhanced two-photon ionization time-of-flight (R2PI-TOF) excitation spectra of supersonically expanded complexes of isomeric 2,3-butanediols with a suitable chromophore, i.e. R-(+)-1-phenyl-1-propanol, represent powerful means for structurally discriminating the diol moiety and for investigating the nature of the intra- and intermolecular interactions involved in the complexes.

R2PI Study of intermolecular hydrogen bond in solvent-free chiral complexes.

One- and two-color, mass selected R2PI spectra of the S(1)<--S(0) transitions in the bare (+)-(R)-1-phenyl-1-ethanol (E(R)) and its complexes with different solvent molecules (solv) (-)-(R)-2-butanol (B(R)) or (+)-(S)-2-butanol (B(S)) and (-)-(R)-2-butylamine (A(R)) or (+)-(S)-2-butylamine (A(S)), have been recorded after a supersonic molecular beam expansion. The one-color R2PI excitation spectra of the diastereomeric complexes are characterized by significant shifts of their band origin relative to that of bare E(R). The extent and the direction of these spectral shifts are found to depend on the structure and the configuration of solv and are attributed to different short-range interactions in the ground and excited states of the complexes. In analogy with other diastereomeric complexes, the phenomenological binding energy of the homochiral cluster is found to be greater than that of the heterochiral one.

Acute intermittent porphyria. A perplexing case.

We report the case of a 58-year-old woman affected by polyneuropathy, vegetative disturbances and abdominal pain. A provisional diagnosis of acute intermittent porphyria was made and was confirmed by the increased levels of urinary delta-aminolevulinic acid (ALA) and porphobilinogen (PBG).

Evaluation of the lumbar spine in patients with glycogen storage disease: CT demonstration of patterns of paraspinal muscle atrophy.

CT studies of the lumbar spine were performed in 19 patients with glycogen storage disease. Nine of 10 patients with McArdle's disease and seven of nine patients with acid maltase deficiency demonstrated posterior paraspinal muscle atrophy out of proportion to their ages. In addition, the psoas muscles were spared in all 10 patients with McArdle's disease and were involved with atrophy in seven of the nine patients with acid maltase deficiency. We conclude that when patients with low back pain-or asymptomatic patients-demonstrate otherwise unexplained atrophy of the paraspinal muscles the diagnosis of glycogen storage disease should be considered. Furthermore, when the psoas muscles are spared, the specific diagnosis of McArdle's disease is suggested.

Venous sinus thrombosis as a cause of parenchymal and intraventricular hemorrhage in the full-term neonate.

A case of parenchymal and intraventricular hemorrhage in a full-term neonate is reported. The underlying cause in our patient is thought to be related to cerebral sinovenous occlusive disease secondary to Protein C deficiency, a rare coagulopathy.

Congenital spondylolisthesis of the 6th cervical vertebra: CT findings.

The CT demonstration of a case of congenital spondylolisthesis of the C6 vertebral body is reported. This entity includes bilateral bony defects in the pars interarticularis regions, deranged facet joints, as well as a midline bony cleft in the spinous process. This congenital deformity should be recognized and not mistaken for traumatic spondylolisthesis.

Heterotopic gray matter. Report of a case.

We report the case of a 40 year old man who presented a tonic-clonic seizure. The CT scan and MRI revealed heterotopic gray matter in the right frontoparietal cortex.

Single fiber EMG and cardiovascular reflexes in botulism: a follow-up study.

A patient with botulism was studied at different times after intoxication using various autonomic tests of the cardiovascular reflexes, and by single fiber EMG (SFEMG). The control of heart rate and blood pressure appeared markedly impaired in the early stage of the disease as well as SFEMG. Autonomic function recovered more slowly as neuromuscular transmission. Monitoring autonomic derangement in botulism may give the opportunity to select patients at risk for cardiac or respiratory arrest.

The pentose phosphate pathway in brain during development.

Sprague-Dawley rats were delivered in our laboratory and decapitated at ages varying between 1 and 60 days. The concentrations of 6-phosphogluconate in extracts of the brain were determined in these litters and in adult rats. The highest of 6-phosphogluconate was seen in brains of 3-day-old rats when it was at that age more than six times the adult level. Turnover rates for this same compound were determined by an in vitro technique at ages 1, 3 and 12 days and in the adult. We conclude that the pentose phosphate pathway is more active in rat brain during early development than in the adult, with a peak occurring at 3 days of life, indicating a possible link to nucleic acid synthesis.