Table I. C-1 mutant peptides: 6HB stability and fusion inhibition.

	Mobs/Mcalc a	[ϑ]222 b	Tm b , c	Tm in 2 M GuHClb , d	IC50 inhibitione
			°C	°C	nM
W3A wt	2.9	−30 167	≥98	88	38 ± 4
L447G	2.7	−28 922	86	72	150 ± 19
L447A	2.8	−29 328	88	78	92 ± 10
L447V	2.8	−29 495	91	81	83 ± 11
L447I	2.8	−29 820	94	83	50 ± 7
L447F	2.9	−29 407	90	79	100 ± 12
L447W	3.1	−29 381	89	79	106 ± 8
I449G	2.9	−25 390	79	67	271 ± 24
I449A	2.8	−27 384	87	74	115 ± 7
I449V	3.0	−28 847	96	85	58 ± 6
I449L	2.8	−29 291	97	87	54 ± 5
I449F	2.9	−27 408	87	74	151 ± 12
I449W	2.9	−27 362	85	73	146 ± 13

^aSedimentation equilibrium data for N-1/C-1 complexes are reported as the ratio of the experimentally determined mol wt to the calculated mol wt for an N-1/C-1 heterodimer.

^bCircular dichroism data for 10 μM each of N-1 and C-1 peptides in PBS, pH 7.0 (units = deg cm² dmol⁻¹).

^cThe midpoint of thermal denaturation (T_m) was estimated from the maximum of the first derivative of [ϑ]₂₂₂ plotted as a function of temperature.

^dThermal melts in the presence of 2.0 M GuHCl.

^eC-1 mutant peptide IC₅₀ values for inhibition of cell–cell fusion using the T7 luciferase reporter gene assay.