Search

Ab initio quantum mechanical calculations of the potential energy surface (PES) of singlet 1, 2-dilithioethene and acetylenic C2H2Li2 isomers reveal the location of three unreported minima, a planar, monobridged trans-1,2-dilithioethene and two acetylenic structures. Coupled cluster method helps determine the vibrational frequencies of all structures and an acetylenic monomer, a Cs complex between lithioacetylene and LiH, is the global minimum on C2H2Li2 PES. Carbon-lithium bonding in all these species exhibits ionic characteristics.

A comparison of the lowest lying triplet and singlet states of extremely unconventional carbene revealed that the nitromethylene's lowest lying triplet state is higher in energy than the lowest lying singlet state, and the triplet state is higher in energy by seven kcal/mol. These are two important reasons why the singlet C1 symmetry structure is equilibrium geometry, not the nonplanar Cs symmetry structure. The Cs structure permits a more conducive electrostatic interaction between the hydrogen and the 'partially' bridged oxygen by keeping these atoms in the regular range of powerful hydrogen bonding. Electron density is donated to the carbon atom that is electron deficient by the low pair on the 'partially' bridged oxygen.

Alzheimer's disease (AD) is a complex and multifactorial neurodegenerative disease, which is currently diagnosed via clinical symptoms and nonspecific biomarkers (such as Aβ 1-42 , t-Tau, and p-Tau) measured in cerebrospinal fluid (CSF), which alone do not provide sufficient insights into disease progression. In this pilot study, these biomarkers were complemented with small-molecule analysis using non-target high-resolution mass spectrometry coupled with liquid chromatography (LC) on the CSF of three groups: AD, mild cognitive impairment (MCI) due to AD, and a non-demented (ND) control group. An open-source cheminformatics pipeline based on MS-DIAL and patRoon was enhanced using CSF- and AD-specific suspect lists to assist in data interpretation. Chemical Similarity Enrichment Analysis revealed a significant increase of hydroxybutyrates in AD, including 3-hydroxybutanoic acid, which was found at higher levels in AD compared to MCI and ND. Furthermore, a highly sensitive target LC-MS method was used to quantify 35 bile acids (BAs) in the CSF, revealing several statistically significant differences including higher dehydrolithocholic acid levels and decreased conjugated BA levels in AD. This work provides several promising small-molecule hypotheses that could be used to help track the progression of AD in CSF samples.