Lysis experiments
The cell pellet was washed three times with amedium containing
140mMNaCl, 5mMKCl, 20mMTris–HCl (pH 7.2), 2mMMgCl2
and 0.1mMEDTA. RBCswere suspended in the same medium used
in the erythrocyte washing and diluted to a hematocrit of 1%. Cell
lysis was measured at 37 ◦C in a medium containing 0, 100 or
200M of chalcogenides (n = 4) after different periods of incubation
Incubations were stopped by centrifugation (2000rpm for 40 s
at room temperature). The degree of cell lysis was determined
according to Young et al. [23] by measuring the extinction of the
supernatant at 540 nm. Complete lysiswas determined by addition
of Triton X-100 (0.01%).