H-1 and C-13 Nmr-Studies on M (egta) Complexes in Aqueous-Solution

EGTA is a kind of highly selective calcium-binding chelate, whose preference for the binding of Ca~(2+) over Mg~(2+) is about 10~6, therefore it is considered as a model for the binding sites in calcium-binding proteins. Although the crystal structure of Ca (EGTA) has been reported, its structure in aqueous solution is still unclear. Considering that Ca~(2+) ionic radius (0.99(?)) falls in the range for those of lanthanide series (1.06—0.85(?)), Ln (EGTA) (Ln=La, Y, Lu and Sc) is studied in this note so as to deduce