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

FIGURE 2.

FIGURE 2

All CPCs investigated bind the sulfated GAG heparin. Isothermal titration calorimetry of various cell-impermeant (A and B) and -permeant compounds (C and D) with heparin. (A–C) Heat flow (same y axis for all three panels). Every 10 min, 5 μl of 15 μM heparin is titrated into the reaction cell (Vcell = 1.4 ml) filled with (A) 100 μM propidium iodide, (B) 100 μM ethidium bromide, or (C) 100 μM acridine orange. (D) Heats of reaction hi (equal to integration of the heat flow peaks) as a function of the number of injections Ni. The heparin concentration in the reaction cell (Vcell = 1.4 ml) is 13.7 μM. Each symbol corresponds to the injection (10 μl every 10 min) of the following compounds: (○) 10.4 mM l-arginine, (•) DOTAP vesicles ([DOTAP]out = 4.8 mM, 30 nm, DOTAP:DOPC = 3:7 (n/n)), (⋄) 650 μM PLL16, (▴) 717 μM LPEI, (★) 1.167 mM nona-l-arginine, (□) 1.302 mM HIV Tat-PTD, and (▪) 1.486 mM penetratin. Symbols represent experimental data. The solid line is a least-squares fit using the binding model described by Eqs. 1 and 2 with the parameters listed in Table 1. Temperature is 28°C. Buffer in all experiments is 30 mM phosphate and 77 mM NaCl at pH 7.40 with a resulting physiological ionic strength of 154 mM.