Page - (000303) - in Biomedical Chemistry: Current Trends and Developments

backbone torsion angles of residues i+1 and i+2. The most common β- turns found in proteins are types I, I′, II, II′, and VIII (Table 3.3.1) (Hutchinson, 1994; Richardson, 1981; Venkatachalam, 1968; Wilmot, 1988). In addition to these, other classes such as III, III′, VIa, VIb and VII have been proposed (Lewis, 1973; Venkatachalam, 1968). The miscellaneous category IV has been introduced to accommodate β-turns that do not fit any specific type. Figure 3.3.5: A β-turn (A) and a γ-turn (B) and examples of a β-turn mimetic (C) (Rosenström, 2006) and a γ-turn mimetic (D) (Rosenström, 2005). The backbone torsion angles phi (φ) and psi (ψ) are indicated for the relevant residues in the peptide turns. Table 3.3.1 Idealized backbone torsion angles for the most common β-turn types (Venkatachalam, 1968; Wilmot, 1988) and the backbone torsion angles for the classic and inverse γ-turn (Matthews, 1972; Nemethy, 1972). The γ-turn is not as common as the β-turn but has been found to be