Section 18.3.2.3.3. Aliphatic residues: leucine, isoleucine, valine

Compared to EH parameterization, the only notable features of the aliphatic residues were the leucine bonds and the C—CA—CB angles of isoleucine and valine. The leucine CD—CG(1,2) bonds retained relatively large σ values, which rather increased compared to the previous values. The C—CA—CB angle values, clustered as bare carbon/tetrahedral CH extended atom/tetrahedral CH₂ extended atom in EH, are sensitive to the degree of substitution at the CB carbon (Table 18.3.2.3, see the discussion of peptide fragments above). The statistics here show that the EH (1991) parameters were too small by about 2°.