(a) PEG residues bind to the lysines in DT. (b) Schematic representation of PEGylation of DT through conjugation of NHS-PEG4 at lysines. (c) Mass spectrometry of DT (left) and PEGyDT (right) samples. DT peak is identified in red and PEGyDT peaks are identified in green. (d) Live- and dead-cell populations after 48 h of incubation with vehicle, DT and PEGyDT in HeLa cells. (e) Time course of cell death after incubation with vehicle, DT and PEGyDT (***P<0.0001, n=3). Statistics were performed using one-way ANOVA test followed by Tukey test. Data are represented as mean±s.e.m. (related to Supplementary Figs 1 and 2).