Reviews the characteristic MRI signal changes of the aging hematoma with a detailed description of the hemoglobin molecule responsible for those changes.
Superinteresting, that behavior from biomolecules so clear explained! And sure not only interesting for medical students. It is so clear and understandable, I enjoyed the lessons in this video, its exceplionally great!
Amazing video thank you!! I have one question - if we said that when the iron ion makes the dative bone it doesnt really contribute any electrons and they come only from the oxygen, then why when the Hb becomes deoxy now iron has unpaired electrons?
Metals, with their partially filled d and f shells, are funny when it comes to their electron configuration and oxidative states. The electron configuration of the nonionic fe metal is [Ar]3d64s2. In the +2 or ferrous state, Fe gives up the two electrons in the outer 4s-subshell making the electron configuration [Ar]3d6. This is the configuration of the normally functioning heme molecule that can transport oxygen around our bodies in the form of oxyhemoglobin. In the ferrous state, oxygen can share it's two free electrons with iron through a dative bond and provide some stability to the iron atom by temporarily restoring the filled 4s-subshell. Because the d-subshell can hold a total of 10 electrons (5 pairs), to maintain stability of the aging heme molecule, Fe will give up another electron leaving a single electron in each of the 5 d-subshell orbitals making the +3 oxidative state or ferric form of iron with an electron configuration of [Ar]3d5. This is methemoglobin. This ferric iron of methemoglobin cannot transport the oxygen molecule around our body because the contribution of the two electrons form oxygen doesn't make this ionic form of Fe more stable. Very cool stuff but a little confusing! Does that help?
Since Fe (II) have 6 coordinate sites so it need 6 lone pairs of electron but there are just 3 coordinate bonds so 3 lone pairs (1 from oxygen and 2 from nitrogen of 2 pyrrole rings) and the other bonds are just covalent bonds (nitrogen of the histidine and 2 of pyrrole rings) ... I find this so much confusing, how this is possible? I tried to search if there are a form of hybridization of Fe(II) that can fit those bonds but no solution.
