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Topic: Complexation and exchange energy in chelation therapy  (Read 2434 times)

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Offline aj3537

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Complexation and exchange energy in chelation therapy
« on: November 25, 2008, 02:11:11 PM »
I am writing a term paper on the different chelators: EDTA, BAL, and D-Penicillamine. In the paper, they compare different metals (lead, zinc, calcium, copper, and iron) and their affinity towards the different chelators. 

M2+ +Ln- -> [M(L)]2-n         ∆Ecomp+ E([M(L)]2-n) – E(Pb2+) – E(Ln-)


[Pb(H2O)8]2+ + [M(L)]2-n-> [Pb(L)]2-n + [M(H2O)]2+
∆Eexch= E([M(H2O)8]2+) + ([Pb(L)]2-n) – E([M(L)]2-n) – E([Pb(H2O)8]2+)


They give these equation in the paper. Can some simply explain what complexation and exchange energy is and how these values work since lead is favored over the other metals:

EDTA
comp     ca   -803     fe   -969   cu   -950   zn   -925    pb   -790
exch      ca   -9.8      fe   24      cu   12      zn   0.4     pb   0

BAL
comp   ca   -508     fe    -679   cu   -700   zn   -671    pb    -557
exch      ca   -70      fe   -33      cu   -6      zn   -21     pb   0

D-Penicillamine
comp   ca    -522    fe    -698   cu     -702    zn   -676   pb    -561           
exch      ca   -60      fe   -19      cu   -8      zn   -19     pb   0               kcal/mol

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