Why is ALA a chelator? Chemistry question. TK?

[Guest guest]

Not doubting Andy but I would like to have a better understanding to

explain to people that ask. Etc

This is a excerpt from a message archive about DMSA

" DMSA is a chelating agent for lead, mercury, etc. In a chemical

sense, " chelation " refers to one molecule grabbing on to a metal atom

with more than one attachment. Thus chelating agents are things that

have more than one attaching group, like DMSA that has 2 sulfurs to

attach to heavy metal atoms. "

I understand that. But if you look at the chemical make up of ALA

where is the two sulfur atoms? I tried to find this in his book. Just

curious thats all.

Thanks