5. Describe the Structure
of the Peptide Bond
Answer:
X-ray diffraction studies of
crystals of small peptides by Linus Pauling and R. B. Corey indicated that the
peptide bond is rigid, and planer. Pauling pointed out that this is largely a
consequence of the resonance interaction of the amide, or the ability of the
amide nitrogen to delocalize its lone pair of electrons onto the carbonyl
oxygen.
Because of this resonance, the C=O
bond is actually longer than normal carbonyl bonds, and the N–C bond of the
peptide bond is shorter than the N–Cα bond. Notice that the carbonyl oxygen and
amide hydrogen are in a trans configuration, as opposed to a cis configuration.
This configuration is energetically more favorable because of possible stearic
interactions in the other.
Assignment submitted by L.Y., Kong, S. H., Lim, S. C., Soo, C. W. Tan and C.C.,Teh 2011/2012 (IBM)
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