TABLE 1.

Biophysical data for Tm(1–131) proteins analyzed by CD spectroscopy

Protein	[θ]222a	[θ]222/[θ]208b	% Helixc	TMd	ΔTMe
			%
Native	39,143 ± 935	1.09 ± 0.04	107 ± 2.6	50.0 ± 0.0
L110A	36,412 ± 549	1.08 ± 0.02	99 ± 1.5	43.8 ± 0.2	6.2 ± 0.2
A109L-1f	34,587 ± 751	1.08 ± 0.04	94 ± 2.0	37.3 ± 0.2	−12.7 ± 0.2
A109L-2f				61.1 ± 0.3	+11.1 ± 0.3

^a Mean residue ellipticity from CD spectra at 222 nm in benign buffer (100 mm KCl, 50 mm PO₄, pH 7) at 5 °C. Protein concentration ranged from 29 to 34 μm monomer. Ellipticity values shown are the average of triplicate experiments with error of ≤2.5%.

^b Ratio of mean residue ellipticity at 222 and 208 nm, benign buffer.

^c Percentage helix is calculated from [θ]_Hⁿ = [θ]_H^∞ (1 − k/n) where [θ]_H^∞ = −37,400 degrees cm² dmol⁻¹ for a helix of infinite length, n is the number of residues in the helix, and k is a wavelength-dependent constant (2.5 at 222 nm). For a 133-residue protein, the theoretical value for 100% helix is −36,697 degrees cm² dmol⁻¹ (91).

^d T_M is the temperature at which 50% of the protein is unfolded.

^e Change in T_M relative to the wild type protein.

^f A109L-1 and A109L-2 refer to A109L domain 1 and A109L domain 2, respectively.