Characterization of elemental sulfur in isolated intact spinach chloroplasts.

Incubation of intact spinach (Spinacia oleracea L.) chloroplasts in the presence of (35)SO(4) (2-) resulted in the light-dependent formation of a chloroform-soluble sulfur-containing compound distinct from sulfolipid. We have identified this compound as the most stable form (S(8)) of elemental sulfur (S(0), valence state for S = O) by mass spectrometry. It is possible that elemental sulfur (S(0)) was formed by oxidation of bound sulfide, i.e. after the photoreduction of sulfate to sulfide by intact chloroplasts, and released as S(8) under the experimental conditions used for analysis.