Such alternative chelators include, but are not limited to, porphyrins; cryptate compounds; bis , tris , and tetracatechol compounds; ethylene bis and its derivatives, various aryl DTPA derivatives, bis 2 ethylenediamine diacetic acid and its derivatives, and macrocyclic chelating ligands such as {HEAD ~ any} of {TAIL ~ various DOTA based chelators} 
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Such alternative chelators include , but are not limited to , porphyrins ; cryptate compounds ; bis , tris , and tetracatechol compounds ; ethylene bis and its derivatives , various aryl DTPA derivatives , bis 2 ethylenediamine diacetic acid and its derivatives , and macrocyclic chelating ligands such as { HEAD ~ any } of { TAIL ~ various DOTA based chelators }
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