FIGURE 4.

ATR amide I bandshapes for proteated gramicidin A predicted from Eqs. 5 and 6 and the normal mode analysis of Naik and Krimm (1986a), (A) for the β^6.3 single-helix conformation, and (B) for the ↑↓β^7.2 double-stranded helix conformation. The thick film approximation is used with a helix tilt of γ_eff = 39° (〈cos² γ〉 = 0.60) to obtain the ATR absorbance with parallel (solid line) and perpendicular (dashed line) polarized radiation. (Dotted lines are corresponding calculations with the thin film approximation, γ_eff = 30°; 〈cos² γ〉 = 0.75). Each component mode has a Lorentzian lineshape with FWHH = 15 cm⁻¹.