Mass spectrometric determination of hydroxylamine photooxidation by illuminated chloroplasts.

A mass spectrometer with a special inlet was used to directly monitor the products evolved when hydroxylamine-treated chloroplasts were exposed to short saturating light flashes. We found that: 1. Molecular dinitrogen was the sole product of hydroxylamine photooxidation, and was formed in an amount equal to twice the O2 evolved during H2O photooxidation. 2. This reaction was driven by Photosystem II, and did not involve Photo-system I-generated superoxide or peroxide. 3. In the presence of 3-(3,4-dichlorophenyl)-1,1-dimethyl urea, N2 was evolved only on the first flash. These results suggested that N2 was formed by the combination of two single-electron oxidation products of hydroxylamine.