The bond of ALA is not as strong as DMSA or DMPS. I've read posts from users on this site saying they used supplements in the past containing large dose ALA and got redistribution syndromes without knowing what was going on or what caused it.
If the study with the rats was from acute mercury poisoning it cannot apply to a long term exposure such as Amalgam poisoning because the mercury did not have enough time to lodge itself in the body as well as cross the blood/brain barrier then convert into inorganic mercury. Inorganic mercury cannot pass the blood brain barrier. In such an occurence as with the rat experiment, of course a single dose of ALA can prove to chelate mercury effectively; it is essential still floating around in their systems.
The brain is constantly letting organic mercury in through the blood/brain barrier and then back out the barrier at a certain rate. If sufficient mercury in either inorganic or organic form is present in the body, mercury is no longer released from the brain at the same rate. What ALA essentially does in the context of a chelation protocol is hold the blood brain barrier open and allow the brain to detox mercury. However, the body MUST have a lower concentration of mercury in it for this natural chelation to work. This is where dmsa and dmps come into play.
The danger is when methylmercury readily enters the brain but does not leave it due to higher concentrations in the body, where it then converts to inorganic mercury and cannot pass the blood brain barrier.
Once again, what ALA really serves in this purpose is holding the blood brain barrier open long enough for the brains natural chelation mechanisms to escort the inorganic mercury through the barrier. It does have the ability to bond to mercury, but given the duration of time it takes for the brain to rid itself of inorganic mercury poisoning (3 years or so) it is evident that ALA is not a magical brain chelator that simply goes in, picks up some mercury, and leaves. It is evident rather that the brain chelates, at its own rate, what it could not due to the inorganic mercury being unable to leave the brain without the help of ALA.