With stricter regulation of atmospheric volatile organic compounds (VOCs) originating from fossil fuel-based vehicles and industries, the use of volatile chemical products (VCPs) and the transformation mechanism of VCPs have become increasingly important to quantify air quality. Volatile methylsiloxanes (VMS) are an important class of VCPs and high-production chemicals. Using quantum chemical calculations and kinetics modeling, we investigated the reaction mechanism of peroxy radicals of VMS, which are key intermediates in determining the atmospheric chemistry of VMS. L2-RSiCH2O2 • and D3-RSiCH2O2 • derived from hexamethyldisiloxane and hexamethylcyclotrisiloxane, respectively, were selected as representative model systems. The results indicated that L2-RSiCH2O2 • and D3-RSiCH2O2 • follow a novel Si–C–O rearrangement-driven autoxidation mechanism, leading to the formation of low volatile silanols and high yield of formaldehyde at low NO/HO2 • conditions. At high NO/HO2 • conditions, L2-RSiCH2O2 • and D3-RSiCH2O2 • react with NO/HO2 • to form organic nitrate, hydroperoxide, and active alkoxy radicals. The alkoxy radicals further follow a Si–C–O rearrangement step to finally form formate esters. The novel Si–C–O rearrangement mechanism of both peroxy and alkoxy radicals are supported by available experimental studies on the oxidation of VMS. Notably, the high yield of formaldehyde is estimated to significantly contribute to formaldehyde pollution in the indoor environment, especially during indoor cleaning.

Identification of differentially expressed proteins between the male and female worm of Schistosoma japonicum may provide new insights into the development of schistosomes, especially the molecular mechanism of female worm maturation induced by the male worm after pairing. Comparative two-dimensional gel electrophoresis (2-DE) and mass spectrometry were employed to separate and identify differentially expressed proteins between the male and female worm after pairing. Soluble and hydrophobic proteins from egg, schistosomulum (14 days), and female and male worms at adult stage (42 days) were separated by a sequential extraction method followed by 2-DE and 2-DE images were constructed. There were 1016 +/- 67, 1808 +/- 89, 1142 +/- 45 and 1288 +/- 32 spots detected for soluble proteins and 1425 +/- 108, 952 +/- 59, 847 +/- 75 and 965 +/- 69 spots for hydrophobic proteins from egg, schistosomulum, and adult stage female and male worms, respectively. The differentially and uniquely expressed proteins from male and female worms after pairing (42 days) include 41 +/- 4 and 23 +/- 2 unique spots for soluble proteins, and 11 +/- 1 and 26 +/- 3 unique spots for hydrophobic proteins, respectively. Matrix-assisted laser desorption/ionization-time of flight and electrospray ionization-tandem mass spectrometry were employed to analyze 12 unique spots from the female worm and 16 unique spots from the male worm for peptide mass fingerprinting and sequencing. The results showed that the main functions of these differentially expressed proteins were in signal transduction, metabolism and transcriptional regulation etc. Comparison of the schistosomes proteome between male and female worms may permit the identification of protein candidates for the development of vaccines or new targets for drug development against schistosomiasis.

Chlorine radicals (·Cl) initiated amine oxidation plays an important role for the formation of carcinogenic nitrosamine in the atmosphere. Piperazine (PZ) is considered as a potential atmospheric pollutant since it is an alternative solvent to monoethanolamine (MEA), a benchmark solvent in a leading CO capture technology. Here, we employed quantum chemical methods and kinetics modeling to investigate ·Cl-initiated atmospheric oxidation of PZ, particularly concerning the potential of PZ to form nitrosamine compared to MEA. Results showed that the ·Cl-initiated PZ reaction exclusively leads to N-center radicals (PZ-N) that mainly react with NO to produce nitrosamine in their further reaction with O/NO. Together with the PZ + ·OH reaction, the PZ-N yield from PZ oxidation is still lower than that of the corresponding MEA reactions. However, the nitrosamine yield of PZ is higher than the reported value for MEA when [NO] is <5 ppb, a concentration commonly encountered in a polluted urban atmosphere. The unexpected high nitrosamine yield from PZ compared to MEA results from a more favorable reaction of N-center radicals with NO compared to O. These findings show that the yield of N-center radicals cannot directly be used as a metric for the yield of the corresponding carcinogenic nitrosamine.