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. 2007 Dec 7;94(6):2142–2149. doi: 10.1529/biophysj.107.113472

FIGURE 3.

FIGURE 3

GAG clustering upon CPC binding. Various cell-impermeant and -permeant compounds are titrated into heparin solution (except control (4b), into pure buffer), and the static right-angle light scattering (λex/λem = 350/350 nm) is recorded. The increase in light-scattering signal demonstrates the formation of larger aggregates of CPCs and GAGs. No comparable scattering signal is produced by the titration of GAGs with structurally related but cell-impermeant compounds 6, 9, and 10. The heparin concentration in the optical cuvette (Vcell = 1.4 ml) is 13.7 μM. Each step corresponds to the injection of 10 μl (every 5 min) of the following compounds: (6) 5.2 mM propidium iodide; (9) 10.4 mM l-arginine; (10) 5.2 mM ethidium bromide; (5) 5.2 mM acridine orange; (8) 1.5 mM penetratin; (4) DOTAP vesicles ([DOTAP]out = 4.8 mM, 30 nm, DOTAP:DOPC = 3:7 (n/n)) into (4a) heparin or (4b) buffer; (2) 650 μM PLL16; (3a–c) 359 μM linear polyethylenimine at (3a) pH 7.4, (3b) pH 5.0, and (3c) pH 3.5; (7) 1.3 mM HIV Tat-PTD; and (1) 1.1 mM nona-l-arginine. Same absolute scale in both panels. Temperature is 28°C. Buffer in all experiments is 30 mM phosphate and 77 mM NaCl at pH 7.40 (ionic strength of 154 mM); except LPEI (3b) at pH 5.0 using 30 mM acetate and 133 mM NaCl (ionic strength of 154 mM), and (3c) at pH 3.5 using 30 mM formate and 141 mM NaCl (ionic strength of 154 mM).