Table 1.

Summary of circular dichroism data for α-helical peptides.

peptide	[θ]222	[θ]208	[θ]190	[θ]222/[θ]208	−[θ]190/[θ]208	% α-helix
α14-A	−17800	−18800	31500	0.95	1.68	53
α14-C1-SH	−14800	−18200	20600	0.82	1.13	44
α14-C1-S−	−19200	−19800	35000	0.97	1.77	57
α14-C1-SO2−	−18200	−19700	32900	0.92	1.66	54
α14-C2-SH	−16200	−17400	27500	0.93	1.58	48
α14-C2-S−	−26100	−26000	47600	1.00	1.83	77
α14-C2-SO2−	−26900	−26600	51600	1.01	1.94	84
α14-C5-SH	−8400	−14700	3200	0.57	0.22	25
α14-C5-S−	−9400	−15700	6400	0.60	0.41	28
α14-C5-SO2−	−11400	−15800	12100	0.72	0.76	34
α14-C10-SH	−9900	−14500	7700	0.68	0.53	29
α14-C10-S−	−4700	−10900	−2600	0.43	0.13	14
α14-C10-SO2−	−7200	−12500	1600	0.58	−0.24	21

CD data were collected at pH 4 (peptides α14-A and α14-CX-SH), pH 7 (peptides α14-CX-SO₂⁻), or pH 8.5 (peptides α14-CX-S⁻) in water with 5 mM phosphate buffer and 25 mM NaCl at 0.5 °C. The percent α-helix was calculated as (100% × [θ]₂₂₂)/(−40000 × (1–2.5/16)). Errors are indicated in the Supporting Information (Table S8).