Molecular orbital calculations may be used to predict the dipole moments of molecules.

(a) Using molecular modeling software and the computational method of your choice, calculate the dipole moment of the peptide link, modeled as a trans-N-methylacetamide (18). Plot the energy of interaction between these dipoles against the angle B for r= 3.0 nm (see eqn 18.22).

(b) Compare the maximum value of the dipole-dipole interaction energy from part (a) to 20 k] mol-1 a typical value for the energy of a hydrogen-bonding interaction in biological systems.

18