prov:value
| - The method of claim 29, wherein X1 and X3 are a hydrogen atom, a lipophilic moiety, a phenyl group, a lower alkyl, alkaryl or aralkyl group and X2 and X4 are cationic groups, or wherein X1 and X3 are cationic groups and X2 and X4 are a hydrogen atom, a lipophilic moiety, a phenyl group, a lower alkyl, alkaryl or aralkyl group.
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