Buffer ΔHion (kcal/mol) ΔHobs(kcal/mol)a ΔHint (kcal/mol) Δn PIPES 2.7 -5.1 ± 0.04 -7.7 ± 0.8 0.82 ± 0.1 HEPES 5.0 -4.45 ± 0.05 ACES 7.4 -1.3 ± 0.08 Tris-HCl 11.7 1.6 ± 0.04 All experiments were performed at 25°C. aGiven errors were calculated by fits to SEDPHAT [4]. bErrors for ΔHint and Δn are derived from the linear regression line of ΔHobs vs. ΔHion plot

Table 1: Titration of APH with netilmicin in different buffers.