Calculated through Vis-Spec difference in absorption at Soret peak, ∆GH20 (without chemical denaturant) of Mb was ~23-30 jK/mol while Hb was ~6-10 jK/mol. What is the biochemical source of this difference? Why is monomeric Mb more stable than tetrameric Hb? My data does not make much biological sense to me.

I found a paper : https://link.springer.com/content/pdf/10.1134/S0006297915040100.pdf which has similar difference in ∆G between Mb and Hb (Lb a monomeric form of Hb was used instead for the study) but they state: "The lower ΔGD values of Lb compared to Mb ...... indicate more structural and conformational stability for Lb".

This is throwing me off even more because I thought higher, more positive ∆GH20 meant the protein is more stable since more energy is required to undergo denaturation but this paper is stating the opposite?

Any help would be appreciated.

Bonus Question:

As temperature increases, Avg. ∆GH20 increases for Hb decreases (ie becomes more unstable which makes sense to me) but for Mb the avg. ∆GH20 increases. Why would this be the case?

I have attached an excel file with all the data and plots I am referring to if that clarifies anything.