. Author manuscript; available in PMC: 2012 Sep 20.

Published in final edited form as: Biochemistry. 2011 Aug 26;50(37):7919–7932. doi: 10.1021/bi200873u

Table 3.

Thermodynamic and kinetic parameters for the mutant peptides binding and insertion in POPC bilayers at room temperature.

Peptide	$Δ G_{bind}^{o}$ ^a (kcal/mol)	$Δ G_{i f}^{o}$ ^b (kcal/mol)	helix (%)			$Δ G_{oct}^{o}$ (kcal/mol)	$Δ G_{oct - i f}^{o}$ ^c (kcal/mol)	Dye release
	$Δ G_{bind}^{o}$ ^a (kcal/mol)	$Δ G_{i f}^{o}$ ^b (kcal/mol)	memb.	water				type ANTS/DPX	τ (s)^d CF
	exp	calc	memb.	exp	calc^e			type ANTS/DPX	τ (s)^d CF
δ-Lysin	−8.5	−5.8	100	53	1	21.9	30.4	graded	2.2
DL-1	−7.0	−1.5	52	~20	1	19.3	26.3	all-or-none	4.9
DL-2a	−7.4	−2.3	54	54	35	23.2	30.6	graded	14.8
DL-2b	−5.7	−6.2	77	59	59	19.7	25.4	–	650
Cecropin A	−6.4	−1.7	63	~10	1	31.1	37.5	all-or-none	~15000
CE-1	−7.0	−6.1	55	~30	3	17.3	24.3	all-or-none	35
CE-2	−5.6	−5.7	70	~30	4	29.6	36.2	graded	11000
Magainin-2^f	−6.1	−3.8 (−6.2)^g	57 (83)	~5	0	20.1	26.2	all-or-none	~20000
MG-1	−7.4	−3.6	69	46	16	18.2	25.6	all-or-none	13.5
MG-2	−6.4	−2.7 (−6.4)	40 (80)	~10	2	19.1	25.5	graded	20000

Calculated from the experimentally determined dissociation constant by $Δ G_{bind}^{o} = ln K_{D} - 2.4 kcal / mol$ .

Calculations of $Δ G_{i f}^{o}$ and $Δ G_{oct}^{o}$ were performed with MPEx (47).

Calculated using the experimental value $Δ G_{bind}^{o}$ for the free energy of binding to the interface.

Measured in LUVs of POPC 50 μM.

Helicity in aqueous solution was calculated with AGADIR.

Binding was measured with the F12W variant of magainin 2. The calculations assume His is neutral in magainin-2 and MG-2, since the experiments were performed at pH 7.5. The value of $Δ G_{bind}^{o}$ for magainin 2 (F12W) on POPC, previously reported as −5.5 kcal/mol (6), which was based on K_D = 5 mM (32), was revised. The value of $Δ G_{bind}^{o} = - 6.1 kcal / mol$ listed here is based on a better estimate of K_D = 2 mM (see Table 2).

Binding of magainin 2 to POPC is too weak to measure helicity accurately. The value of −3.8 kcal/mol is calculated using the helicity (57%) that we measured in POPC/POPG 1:1. The value of −6.2 is calculated using the helicity (83%) determined from NMR in DPC micelles (64).