The hydrogen peroxide ( H 2 O 2 ) molecule plays an important role in stratospheric ozone chemistry as a reservoir molecule in the HO X cycle. The Superconducting Sub-Millimeter-Wave Limb Emission Sounder (SMILES) instrument in the Japanese Experiment Module (JEM) on the International Space Station monitors H 2 O 2 using the pure rotational J Ka , Kc = 20 1 , 19 – 19 2 , 17 transition at 625.044 GHz in the ground vibronic state. Accurate retrievals of H 2 O 2 abundances rely on a knowledge of pressure broadening effects for this transition, and the required nitrogen ( N 2 ) and oxygen ( O 2 ) broadening coefficients are measured here for the first time. Values of the pressure broadening coefficients, γ ( N 2 ) = 4.03 ± 0.06 MHz / Torr and γ ( O 2 ) = 2.49 ± 0.04 MHz / Torr are obtained at room temperature, with statistical 3 σ uncertainties given. The value for air broadening is then derived to be γ ( air ) = 3.71 ± 0.09 MHz / Torr , where the uncertainty includes possible systematic errors.
Research Containing: Hydrogen Peroxide
Oxalate oxidase (OXO) utilizes oxalate to generate hydrogen peroxide, and thereby acts as a source of hydrogen peroxide. The present study was carried out to investigate whether apoplastic OXO modifies the metabolism of cell wall-bound ferulates in wheat seedlings. Histochemical staining of OXO showed that cell walls were strongly stained, indicating the presence of OXO activity in shoot walls. When native cell walls prepared from shoots were incubated with oxalate or hydrogen peroxide, the levels of ester-linked diferulic acid (DFA) isomers were significantly increased. On the other hand, the level of ester-linked ferulic acid (FA) was substantially decreased. The decrease in FA level was accounted neither by the increases in DFA levels nor by the release of FA from cell walls during the incubation. After the extraction of ester-linked ferulates, considerable ultraviolet absorption remained in the hemicellulosic and cellulose fractions, which was increased by the treatment with oxalate or hydrogen peroxide. Therefore, a part of FA esters may form tight linkages within cell wall architecture. These results suggest that cell wall OXO is capable of modifying the metabolism of ester-linked ferulates in cell walls of wheat shoots by promoting the peroxidase action via supply of hydrogen peroxide.