prov:value
| - are hydrogen or E-F, a polar group wherein E is a spacer group having the structure --(CH2)n -- and n of said spacer group=0, 1, 2, 3, or 4, and F is hydroxy, sulfonate, sulfate, carboxylate, or a lower alkyl substituted amino; and when any one of said R1 and R2 groups is not selected from one said reactive moiety, said remaining R1 or R2 are a lower alkyl or said E-F and n of said spacer group=1,
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