ABSTRACT
Here we report on the gas-phase interactions between protonated enantiopure amino acids (L- and D-enantiomers of Met, Phe, and Trp) and chiral target gases [(R)- and (S)-2-butanol, and (S)-1-phenylethanol] in 0.1-10.0 eV low-energy collisions. Two major processes are seen to occur over this collision energy regime, collision-induced dissociation and ion-molecule complex formation. Both processes were found to be independent of the stereo-chemical composition of the interacting ions and targets. These data shed light on the currently debated mechanisms of gas-phase chiral selectivity by demonstrating the inapplicability of the three-point model to these interactions, at least under single collision conditions. Graphical Abstract.
Subject(s)
Amino Acids/chemistry , Protons , Butanols/chemistry , Gases/chemistry , Methionine/chemistry , Models, Molecular , Phenylalanine/chemistry , Phenylethyl Alcohol/chemistry , Stereoisomerism , Tandem Mass Spectrometry , Thermodynamics , Tryptophan/chemistryABSTRACT
In a cohort of 113 children prospectively followed from birth to the age of 3, two subgroups were discerned: one with recurrent acute otitis media (rAOM), the other subgroup with no AOM at all ("healthy" children). At further follow-up at the age of 10, no child had AOM or secretory otitis media (SOM), but between 3 and 7 y of age the rAOM subgroup was characterized by a significantly higher incidence of AOM as well as protracted secretory otitis media (SOM) episodes than was the "healthy" subgroup. The two subgroups did not differ significantly in hearing-thresholds at pure tone audiometry. After the age of 7, the incidence of AOM was the same in both groups. It is concluded that children with frequent AOM episodes before the age of 3 need long-term follow-up to school age, but seem not be predisposed to chronic SOM.
