CH908, Problem set 15 - Photodissociation spectroscopy
1. How many infrared photons of 10.6 μm (minimum) are needed to
allow a conformation change so that the His5 conformation changes
to the His1 conformation? See the lecture notes for the transition
state energies.
2. How many infrared photons of 10.6 μm (minimum) are needed to
allow a conformation change so that the His5 conformation changes
to the His3 conformation? See the lecture notes for the transition
state energies.
3. How many infrared photons of 10.6 μm are needed if the energy
from these infrared photons is redistributed into 60 normal vibrational
modes - assume that the modes are close coupled, the vibrational
modes are all the same in energies, and that no photons are lost
radiatively. (note: these are terrible assumptions normally, but this
crude calculation can give order-of-magnitude estimates). 60 normal
modes is expected for a molecule with 22 atoms (number of modes =
3n-6).
4. A normal peptide bond has a bond dissociation energy in the 4-5
eV range. Can you estimate the minimum number of photons and
also the fully averaged number of photons (same assumptions as #3)
for an average 10-mer peptide?
5. How do the assumptions perturb these estimates?