Patent ID: 7399613

Claim:
A compound having the formula: wherein X, Y, Z, A and B are independently selected linking groups which are members selected from O, NR, S and CH 2 ; wherein R is a member selected from H, an acetyl group, a water-soluble polymer, and a linker to a water-soluble polymer; R 1 , R 2 , R 3 , R 4 and R 5 are members independently selected from H, an acetyl group, a poly(alkylene oxide), and a linker joined to a poly(alkylene) oxide; R 6 is a member selected from H, OH, an acetyl group, and a poly(alkylene oxide); and i + is a cation, with the proviso that at least one of R, R 1 , R 2 , R 3 , R 4 , R 5 and R 6 is a member selected from a poly(alkylene oxide), and a linker joined to a poly(alkylene oxide).