Table 1. Summary of Force Field Torsion Reparametrizations Relative to AMBER ff99^a.

parametrization	altered torsions	reference
parmbsc0	α, γ	(41)
parm99χ_Yil	χYil	(42)
ff10	α, γ, χ ff10	(43)
parmTor	α, β, γ, ϵ, ζ, χ Yil	(44)

^aAll α/γ changes are from parmbsc0 (cf. Figure 1 for torsion definitions). Parm99χ_Yil and ff10 use different quantum mechanical methods to derive χ. All force fields are based on the ff94 partial charge⁶⁷ and van der Waals model.