(CO2)n+, (H2O)n+, and (H2O)n+ (CO2) gas cluster ion beam secondary ion mass spectrometry: analysis of lipid extracts, cells, and Alzheimer’s model mouse brain tissue

This work assesses the potential of new water cluster-based ion beams for improving the capabilities of secondary ion mass spectrometry (SIMS) for in situ lipidomics. The effect of water clusters was compared to carbon dioxide clusters, along with the effect of using pure water clusters compared to mixed water and carbon dioxide clusters. A signal increase was found when using pure water clusters. However, when analyzing cells, a more substantial signal increase was found in positive ion mode when the water clusters also contained carbon dioxide, suggesting that additional reactions are in play. The effects of using a water primary ion beam on a more complex sample were investigated by analyzing brain tissue from an Alzheimer’s disease transgenic mouse model. The results indicate that the ToF-SIMS results are approaching those from MALDI as ToF-SIMS was able to image lyso-phosphocholine (LPC) lipids, a lipid class that for a long time has eluded detection during SIMS analyses. Gangliosides, sulfatides, and cholesterol were also imaged. Graphical abstract

Homogeneous nucleation of carbon dioxide in supersonic nozzles II: molecular dynamics simulations and properties of nucleating clusters

Molecular dynamics simulations reveal the structural and energetic properties of carbon dioxide clusters nucleating in the gas phase at extreme undercooling.

Theoretical studies on clusters of carbonate with carbon dioxide, CO31–/2–(CO2)n, for n = 1–5 — Comparison of carbonate clusters with sulfate clusters

Density functional theory (DFT) calculations were performed on the geometries and energies of CO31–/2–(CO2)n clusters with n = 1–5. For small clusters (n = 1 or 2), coupled cluster energies were obtained. Up to three CO2 molecules are bound covalently to the dianion. Only weak electrostatic bonds were found in the monoanions. Calculated binding energies for the monoanions are in reasonable agreement with experimental values. The calculated adiabatic electron detachment energy for the dianion is –0.07 eV at n = 5, indicating that at least six CO2 molecules will have to be added to CO32– before the dianionic cluster becomes, in the gas phase, more stable than the monoanionic one. In comparison, for sulfate – carbon dioxide clusters, stabilization occurs at n = 2. Carbonate clusters are compared with sulfate clusters for three solvent molecules: CO2, SO2, and H2O. Carbonate clusters have larger binding energies than sulfate clusters. For a given dianion, binding energies are largest for SO2 and smallest for H2O. However, in all cases, stabilization of the carbonate dianion by clustering is more difficult to achieve than stabilization of the sulfate dianion.