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3.2 Sheets
3.2.2 Parallel
The hydrogen bonds in a parallel beta sheet are not perpendicular to the
individual strands resulting in component (~1/3 of the peptide dipole)
parallel to the strand. The parallel sheet then has an overall macrodipole
leaving the an effective charge of ~ +1/15 unit elemental charge at the
N-terminus and - 1/15 charge at the C-terminus of each strand of average
length (~5 times less than an average alpha helix macrodipole). An example
of a mixed beta sheet containing an parallel component is given using the
protein thioredoxin (Figure 10 ).
Figure 11. The three-stranded parallel beta sheet in thioredoxin
(2TRX.PDB). The three parallel 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.
download 2TRX.PDB
download RasMol script for parallel sheet
No Title - 31 MAY 96
written by Kurt D. Berndt
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