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Measurements of iron uptake, ionic dissociation and radiolytic stability of the mycobacterial iron complex ferrimycobactin S (FeMy) were carried out using ''Fe as a radioactive tracer. The effect of gamma irradiation was studied using labeled FeMy prepared by reaction of mycobactin S with s 'FeCl 3 . The major effect of radiation is release of iron from FeMy (21% loss at 4.4 MGy), probably due mainly to reduction of Fe (III) by radiationgenerated electrons. Transfer of iron to and from mycobactin S in chloroform solutions was followed by extraction procedures using acidic aqueous phases, under either isohydric or isochronal conditions. The basic mechanism of iron uptake and release is shown to be governed by the competition of the Fe 3+ ions with the acidic protons in combining with the mycobactin complexation sites. For an overall description of the data, however, it is necessary to invoke an additional process based on the association of Fe 3+ with the CI" counterions to yield neutral FeCl 3 molecules which inhibit incorporation of Fe into mycobactin S.

Comportement chimique de forme par captuie electronique du en phase gazeuse. I. Methane 59 Comportement chimique de Tiode 125 forme par capture electronique du xenon 125 en phase gazeuse I. M6thanePar J. J.

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