ABSTRACT
Investigating the structural characteristics of proton tautomers is of great significance for understanding organic reactions and biochemical processes.In this study,a method based on ion mobility mass spectrometry combined with ab initio molecular dynamics calculations was proposed.The structures of proton tautomers were determined by comparing the experimental and theoretical collision-induced dissociation(CID)mass spectrograms of different proton tautomers.Ion mobility mass spectrometry was used to separate proton tautomerism produced during ionization.The CID mass spectra of each isomer could be obtained after mobility separation.The quantum chemical mass spectrometry(QCXMS)program based on ab initio molecular dynamics calculations was used to calculate the fragmentation process and obtain the theoretical CID mass spectra.The results of experiment and calculation showed that this method effectively solved the issue of difficult identification of proton tautomers.This method was also of great significance for the study of ionization mechanism and organic reaction process using mass spectrometry.
ABSTRACT
<p><b>Background</b>Asthma is a common chronic respiratory disease and is related to air pollution exposure. However, only a few studies have concentrated on the association between air pollution and adult asthma. Moreover, the results of these studies are controversial. Therefore, the present study aimed to analyze the influence of various pollutants on hospitalization due to asthma in adults.</p><p><b>Methods</b>A total of 1019 unrelated hospitalized adult asthma patients from Northeast China were recruited from 2014 to 2016. Daily average concentrations of air pollutants (particulate matter <2.5 μm [PM], particulate matter <10 μm [PM], sulfur dioxide [SO], nitrogen dioxide [NO], and carbon monoxide [CO]) were obtained from the China National Environmental Monitoring Centre website from 2014 to 2016. Cox logistic regression analysis was used to analyze the relationship between air pollutants and hospital admissions in adult asthma.</p><p><b>Results</b>The maximum odds ratio (OR) value for most air pollutants occurred on lag day 1. Lag day 1 was chosen as the exposure period, and 8 days before onset was chosen as the control period. Three pollutants (PM, CO, and SO) were entered into the regression equation, and the corresponding OR (95% confidence interval) was 0.995 (0.991-0.999), 3.107 (1.607-6.010), and 0.979 (0.968-0.990), respectively.</p><p><b>Conclusions</b>A positive association between hospital admissions and the daily average concentration of CO was observed. CO is likely to be a risk factor for hospital admissions in adults with asthma.</p>