Table 1.

Mechanical Parameters of 75POPG:25POPC Monolayers in the Presence of 1 μM of GsMTx4 and Several K-E Analogs

Analog	Breaking Point		2nd Minimum		1st Minimum		n
	A (Å2)	π (mN/m)	Cs−1 (mN/m)	π (mN/m)	Cs−1 (mN/m)	π (mN/m)
Control	66.0 ± 2.9	41.7 ± 2.9	–	–	–	–	9
WT	89.8 ± 4.1	38.7 ± 0.9	14.3 ± 2.6	39.5 ± 0.5	32.2 ± 4.0	26.1 ± 1.5	10
K8E	51.7 ± 3.2	43.7 ± 0.9	13.7 ± 2.3	36.9 ± 0.9	21.3 ± 2.2	30.8 ± 1.1	8
K15E	52.3 ± 2.2	43.7 ± 0.2	21.8 ± 1.2	40.5 ± 0.6	19.7 ± 1.0	26.4 ± 0.3	4
K25E	59.8 ± 1.8	47.1 ± 0.6	–	–	22.2 ± 1.5	29.3 ± 1.7	8
K28E	56.7 ± 7.2	43.8 ± 1.4	13.3 ± 2.5	35.5 ± 1.0	20.5 ± 1.4	28.8 ± 0.7	4

Breaking point of isotherms signifies the change of slope, which in case of WT shows the early onset of peptide expulsion. For all other analogs an obvious isotherm flattening was associated with collapse. The position of the second minimum of the inverse compressibility parameter Cs₂⁻¹ reflects “softening” of the monolayer associated with pressure-dependent redistribution of the peptide to a shallower position. The second minima are low for the active peptides, but are either higher for the compromised peptides (K15E), or may not even exist (K25E). The first Cs₁⁻¹ minimum presumably reflects compaction and ordering of the peptides within the still expanded monolayer and its position shows no direct correlation with activity. The number of experiments is shown in the last column (n).