Selective interaction of SS-31 and [ald]SS-31 with CL-containing bilayer membranes and the mitochondrial inner membrane. (A) Diagram of the cross-section through a TOCL-POPC liposome. (B) Diagram of the cross-section through a CL-POPC-DHPC bicelle. (C) The fluorescence emission spectra (in arbitrary units; au) of [ald]SS-31 alone and in the presence of POPC liposomes (upper panel, I), TOCL-POPC liposomes (upper panel, I), TOCL-POPC-DHPC bicelles (middle panel, II), or cyt c-depleted mitoplasts (bottom panel, III). Two lines correspond to 535 and 465 nm peaks for [ald]SS-31 alone and in the presence of CL-containing bilayers respectively. (D) SS-31 dose dependently increases turbidity of TOCL-POPC liposomes, but not POPC liposomes. (E) SS-31 increases the turbidity of CL-containing bicelles, but not those containing only PC. All data are shown as means ± SEM, n = 4–6. ***P< 0.001, significant effects of SS-31; Student's t-test.