The Chemistry of Human Exposure to Aluminium (Part One)
There are three simple rules to follow
What do we need to know about the chemistry of aluminium in order to understand its biological availability in humans?
There are some simple rules to follow:
Rule Number One
The form of aluminium which is bound by functional groups on biomolecules is its free trivalent aqueous cation, Al3+(aq).
What could be simpler.
Do not, for example, be confused by the pH-dependent hydrolytic chemistry of aluminium (Equation1 below).
Al3+(aq) ↔ AlOH2+(aq) ↔ Al(OH)2+(aq) ↔ Al(OH)3(aq) ↔ Al(OH)4-(aq) (1)
While the distribution of these monomeric forms of aluminium is dependent upon the pH of the environment (or physiological milieu), for example, the aluminate anion (Al(OH)4- (aq)) and the divalent cation (AlOH2+(aq)) being the predominant forms of soluble aluminium at pH above 7.0 and around pH 5.0, respectively. It is the Al3+(aq) cation which will determine any subsequent chemistry and be bound by, for example, a functional group on a protein.
It is the Al3+(aq) which forms the strongest bonds with biomolecules.
The equilibria governing the distribution of the aqueous monomers of aluminium (Equation 1) are practically instantaneous. This means that as soon as Al3+(aq) is bound by any functional group, the equilibrium shifts to replace it, and this will continue until a new equilibrium position is reached between the new aluminium complex and Al3+(aq) and the sum of its hydrolytic forms (Equation 2).
Al-Complex ↔ Al3+(aq) ↔ AlOH2+(aq) ↔ Al(OH)2+(aq) ↔ Al(OH)3(aq) ↔ Al(OH)4-(aq) (2)
So, when the iron transport protein transferrin binds aluminium in the blood at pH 7.4 (where Al(OH)4-(aq) is the predominant hydrolytic form of aluminium) or a carboxylate ligand on a fish gill epithelium binds aluminium in water at pH 5.0 (where AlOH2+(aq) is the predominant hydrolytic form of aluminium) in both cases, it is Al3+(aq) which is bound.
This is rule number one and without this knowledge and understanding you cannot understand human exposure to aluminium.
I will write about rule number two in a subsequent post.
I had to read that multuple times, (my chemistry is very rusty, if it ever was good enough), so the take away...Al3+ is always the (bioavailabe form?) doing the binding with human proteins, irrespective of pH, and thus the "name" of the chemical complex (?). Now I need to know why Al3+ is significant....waiting for part 2.
Thank you for taking the time to explain Al.
Dear Dr. Exley, is hydrous sodium aluminosilicate (zeolite) used in metal detox remedies possibly harmful? I have been tempted to try a heavy metal detox product that contains the ingredient mentioned. I am reluctant to try it because it might add to the Al burden in my body which I am purging with high silica mineral water.
Thank you