- the more optimal orientation of the interstrand hydrogen bonds
- peptide bond dipoles of nearest neighbors within an strand cancel
=> in the parallel sheet, components of the dipoles parallel to the strands align and may interact unfavorably.
Figure 10. The three-stranded antiparallel beta sheet in the protein thioredoxin (2TRX.PDB). The three antiparallel strands are shown in both cartoon format (left) and in stick form containing backbone atoms N, CA, C, and O' (right). Hydrogen bonds are identified by arrows connecting the donor nitrogen and acceptor oxygens. Strands are numbered according to their relative position in the polypeptide sequence.
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RasMol script for antiparallel sheet