chbare Posted July 11, 2017 Share Posted July 11, 2017 Hi Kenny, the chief way cyanide antidotes work is not really centered around directly acting on cytochrome c oxidase, but rather haemoglobin; at least in the case of the traditional therapy (Nitrates + Methylene Blue). As I outlined in the video, the traditional therapy changes the oxidation state of the Iron atom in the porphyrin ring of the sub units of haemoglobin. Typically, the Iron will be in a default configuration of +2/Fe II/Ferrous. Nitrates and other substances can further oxidise the Iron into the +3/FeIII/Ferric state. For reasons that I cannot pull out of my head (I suspect it has to do with the fact that Fe III is a strong Lewis acid and would not be able to coordinate reversibly with the Oxygen molecule.) Fe III does not coordinate with the Oxygen molecule. It however does coordinate exceptionally well with cyanide. This will create a situation where kinetics and thermodynamics favour cyanide coordination with the haemoglobin as opposed to the Iron in the cytochrome c oxidase enzyme. However, this also means the patient has methaemoblobin toxicity and could develop histotoxic hypoxia due to ineffective haemoglobin function. Hence, the need to administer agents that can reduce haemoglobin such as methylene blue. However, the other antidote modality in the United States works very differently. Hydroxocobalamin is a vitamin B12 precursor that contains a Cobalt atom configured in a way that allows it to have a high affinity for the cyanide molecule. The high affinity favours the coordination of cyanide with the Cobalt as opposed to the Iron in cytochrome c oxidase. Again, the exact details are complex, but chemical kinetics and thermodynamics favour Cobalt coordination in this case. A relatively inert molecule known as cyanocobalamin is produced in a 1:1 manner (1 mole of hydroxocobalamin can coordinate with 1 mole of cyanide) that is easily eliminated in the urine. Hopefully that helps out a bit. No worries about being a student. Do not let anybody make you think humanity has developed a deep understand of these things. Much of the universe is a complete mystery to us and as you progress along your educational pathway, you will likely be disturbed from how inadequate and uncertain you feel at each step along the process. My experience has been that with every degree that I have obtained, I had the expectation that I would emerge with a more comprehensive understanding of the world. Every step left me lacking significantly. This was not due to lack of trying or failure of dedication, but a fundamental part of the uncertainty of being a human being attempting to understand a vast and complex universe. Point being, I do not want you to be discouraged. Quote Link to comment Share on other sites More sharing options...
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.