As asked in the title, would the various salts -such as hydrochloride or methyl iodide- of V-Agents interact any differently with acetylcholinesterase compared to the neutral compound? For instance, would the interactions between 33-SN and AChE differ in any way from those between 33-SN+ and AChE? Also, would the phosphoryl-thiocholine analog of Soman have different interactions with AChE compared to Soman itself? In short, would a set of organophosphate AChE inhibitors which only differ in whether the leaving group during the process of AChE inhibition is a fluorine, dialkylaminothiolate, or thiocholine, interact differently with AChE??


1 Answer 1


As a matter, of fact, yes, uncharged phosphoryl thiocholines do seem to interact with acetylcholinesterase differently compared to their charged analogs. For example, it has been reported that

Sundwall (1961) reported that P2S was considerably more effective as an antagonist of the lethal action of 37 SN +(isopropoxy-2-trimethylammonio-tiomethylphosphino oxide) in mice than it was of those of Sarin and 37 S-N (isopropoxy-2-dimethylaminothiomethylphosphine oxide).

P2S refers to the methyl sulfonate salt of pralidoxime. This would seem to suggest that, at least in the case of 37-SN+, the adduct formed by the charged inhibitor is more susceptible to reactivation by oxime therapy as opposed to that formed by the neutral compound†.

Regarding the second half of the question, the answer is also yes. According to Boskovic, Acetylcholinesterase that has been inhibited by O-pinacolyl S-2-diethylmethylammonioethyl methyl phosphonothioate methyl sulfate undergoes aging two orders of magnitude more slowly compared to AChE that has been inhibited by Soman, and is also more susceptible to reactivation. The explanation proposed by the author is that the interaction between a phosphoryl-thiocholine and AChE results in the formation of an adduct in which the phosphoryl group is oriented differently compared to the adduct formed as a result of inhibition by an uncharged organophosphate. The author also points out that AChE which had been inhibited by the compound Ro 3-0411 is more easily reactivated compared to AChE inhibited by diisopropyl fluorophosphate.

In conclusion, it can be said that, for a set of organophosphorus compounds which only differ in whether the leaving group during AChE inhibition is a fluorine atom, a thiocholine, or dialkylaminoethylthiolate (And in which the other side chains are the same), each of these compounds would interact with AChE differently, which influences, probably among other things, their susceptibility to reactivation by oximes and the rate at which the inhibited enzyme undergoes aging.

†It should be noted that, under physiological conditions, some amount of these neutral compounds becomes protonated, although I do not know to exactly to what extent and how and if that affects their pharmacology.


BOSKOVIC, B. (1981). The treatment of soman poisoning and its perspectives. Fundamental and Applied Toxicology, 1(2), 203–213. doi:10.1016/s0272-0590(81)80059-0 

BošKović, B., Maksimović, M., & Minić, D. (1968). Ageing and reactivation of acetylcholinesterase inhibited with Soman and its thiocholine-like analogue. Biochemical Pharmacology, 17(8), 1738–1741. doi:10.1016/0006-2952(68)90237-2


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