Iron chelation. Ferric ammonium citrate in buffer plus DMSO exhibits an absence of absorbance in the visible region (curve 1). Solutions of 3 chelators in DMSO were identical to curve 1. In contrast, iron chelation by 3 hydroxamic acids is illustrated by color development: curve 2, SAHA; curve 3, TSA; and curve 4, desferrioxamine. These data confirm iron chelation by all 3 hydroxamic acids, DFO, TSA, and SAHA.