Table III.

Effects of Termini Changes on the NMR Structuring Diagnostics of -WIZGKW-^a

Sequence	Turn G	Hairpin	CSD (ppm)
	ΔδHα	<frCSD>b	S-2 W Hε3	S+2 W Hε3	S+4 HNE
Ac-WINGKW-NH2	0.287	≤0.45 (∼.42 CD)	-0.378	-0.738	n. a.
Ac-TWINGKW-NH2	0.278	≤0.30 (∼.1 CD)	-0.570	-0.384	n. a.
PWIpGKW-NH2	n.a. c	0.79 ± 0.11	-0.269	-1.856	n. a.
Ac-WINGKWT	0.284	≤0.45	-0.193	-0.603	n. a.
Ac-WINGKWT-NH2	0.393	0.77 ± 0.04	-0.380	-1.680	-2.7 d
Ac-WIPGKWTG-NH2	n.a. c	< 0 >	-0.05	0.05	-1.08
Ac-WIpGKWTG-NH2	n.a. c	0.95 ± 0.03	-0.25	-1.87	-3.06
Ac-WINGKWTG-NH2	0.404	0.78 ± 0.04	-0.379	-1.556	-2.71
WINGKWTG	0.079	0.15 ± 0.10	-0.05	-0.11	-1.11
TWINGKWTG	0.469	0.81 ± 0.10	-0.407	-1.923	-0.48
Ac-TWINGKWTG-NH2	0.454	0.69 ± 0.08	-0.528	-1.620	-1.05
ATWINGKWTG	0.519	≅0.78	-1.354	-0.758	+0.11
KAVWINGKWTVE	0.589	≅0.85	-1.922	-0.280	+0.55

^aCD melts for 7 of the peptides listed, including ATWINGKWTG (which has a mixed W/W geometry with the EtF form predominating) appear in a supporting Figure.

^bWe employ the CSDs at six backbone sites in the common WIZGKW sequence to estimate the hairpin population; the backbone chemical shifts are given in full in the Supporting Information. The reported <frCSD> values are the average (and standard error) of the fHP values derived from these sites assuming that Ac-WIPGKWTG-NH₂ represents zero folding and that the best folded species (Ac-WIpnKWTG-NH₂) represents f_HP = 0.98. This measure does not apply to the longer hairpins in the last two entries

^cThe turn Gly ΔδHα measure does not apply to Pro-Gly turns¹⁶ and appear to be of diminished magnitude in NG species with the FtE W/W interaction. 100% folded values for Gly ΔδHα of NG turn hairpins from the literature are 0.55-0.72 ppm.¹⁶,²⁷,³³,³⁴

^dCSD increases to -3.26 ppm at 270K in 20% glycol, with a proportionate increase in the S+2 Hε3 structuring shift.