TABLE 1.

Secondary structure analysis of nonmutated CAC and CACW40A as determined by FTIR

	Percentage of secondary structure
Wavenumber (cm−1)*	Nonmutated CAC	CACW40A	Structural assignment†
1673.7	9.4	8.2	Turns
1660.3	15.2	6.9	310-helix/α-helix
1650.1		48.7	α-helix
1647.1	41.3		α-helix
1635.5	17.0	23.6	—‡
1625.7	9.8	6.3	Extended chains

^*Errors in the wavenumbers are estimated to be ±2 cm⁻¹.

^†There is one more band centered at 1614 cm⁻¹. This band is assigned to the amino-acid side chains (49) and it accounts for 6% of the total area of the amide I′ band. The percentages of secondary structure shown in the table do not take into account the contribution of this band. The 1673.7 cm⁻¹ component corresponds to turns (49); the 1660.3 cm⁻¹ band is assigned to 3₁₀- and α-helix structures (50,51); the 1650.1 and 1647.1 cm⁻¹ bands are assigned to α-helix (49,52); and the 1625.7 cm⁻¹ band is assigned to extended chains (50).

^‡The assignment of the 1635.5 cm⁻¹ band remains ambiguous (51–53), since it has been reported that it can arise from extended segments that do not form sheets, distorted helical, and/or β-structures.