# Thermal Physics - Absorbtion of oxygen in a magnetic field

1. Mar 27, 2006

### NIQ

Question:
Suppose that at most one $$O_2$$ can be bound to a heme group (see Problem 8), and that when $$\lambda(O_2) = 10^{-5}$$ we have 90 percent of hemes occupied by $$O_2$$. Consider $$O_2$$ as having a spin of 1 and a magnetic moment of 1 $$\mu_B$$. How strong a magnetic field is needed to change the adsorption by 1 percent at T = 300K? (The Gibbs sum in the limit of zero magnetic field will differ from that of Problem 8 because there the spin multiplicity of the bound state was neglected.)

And for reference here is Problem 8 (however we were not required to do this question so I don't know the answer to this one either).:

Problem 8 - Carbon Monoxide Poisoning:
In carbon monoxide poisoning the CO replaces the $$O_2$$ adsorbed on hemoglobin (Hb) molecules in the blood. To show the effect, consider a model for which each adsorption site on a heme may be vacant or may be occupied either with energy $$\epsilon_A$$ by one molecule $$O_2$$ or with energy $$\epsilon_B$$ by one molecule CO. Let N fixed heme sites be in equilibrium with $$O_2$$ and CO in the gas phases at concentrations such that the activities are $$\lambda(O_2) = 1 x 10^{-5}$$ and $$\lambda(CO) = 1 x 10^{-7}$$, all at body temperature 37 derees Celcius. Neglect any spin multiplicity factors. a) First consider the system in the absence of CO. Evaluate $$\epsilon_A$$ such that 90 percent of the Hb sites are occupied by $$O_2$$. Express the answer in eV per $$O_2$$. b) Now admit the CO under the specified conditions. Find $$\epsilon_B$$ such that only 10 percent of the Hb sites are occupied by $$O_2$$.

I know you guys ask for us to show that we've done some work on the question before submitting it but I really have no idea where to start on this one. I haven't talked to any classmates yet because they haven't started anything but if necessary I can see if I can get it started then post what I have before asking for help. I was just hoping someone here could get me going on some sort of solution.

Thanks.

Note: Again, Problem 8 was not assigned so I'm assuming it is not required to be done so don't worry about that one.

Last edited: Mar 27, 2006