prov:value
| - wherein X is as defined above, B is a protein or lipid residue, n is a number from 1 to 12, or if R1, R2 and R3 are hydrogen atoms, both V's together are the group ##STR3## wherein X is as defined above, w is the number 1, 2 or 3, provided that at least two of the substituents Y represent metal ion equivalents of an element with an atomic number of 21 to 29, 42, 44 or 57 to 83.
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