(1) Clinical MRIs typically operate at 1.5 Tesla. At equilibrium, the excess pop
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Question
(1) Clinical MRIs typically operate at 1.5 Tesla. At equilibrium, the excess population of spin-up vs. spin-down protons in a field of this strength is 5 parts in 10^-6. (a) What is the energy difference, in kcal/mol, between these water proton spin orientations (b) What would it be in the best available MRI magnets, which are at 7 Tesla? (2) Two residues that are close to each other in the crystal structure of a protein are mutated to Cys so that they form a disulfide bond with each other. Assuming that there is no distortion of the native structure due to the disulfide bond, what effect would you predict this mutation to have on the Delta G, Delta H, and Delta S of the unfolding of the protein? (3) The following are data for the equilibrium constant for the unfolding of a protein as a function of temperature: What are the Delta H, and Delta S of unfolding of this protein?Explanation / Answer
1)
a) The enrgy gap between two nuclear spin states is given by the formula,
= h Bo
where is gyromagnetic ratio which is constant for a particular nucleus (for H nucleus,it is 42.58 MHz/Tesla)
h is Planck's constant whose value is 6.626 x 10-34 Joule-sec
Bo is magnetic field strength
Energy difference, = 42.58 x 6.626 x 1.5
= 423.2
b) when magnetic fields are 7 tesla,
energy difference = 42.58 x 6.626 x 7
= 1974.94
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