Characterization of polyanions for varying σ.

%-Modification	Degree of polymerizationa	No. of modified residues per chain (m)	Linear charge density (σ)	f PEG (%)
0%	82	0	1.0	9.6
PEG-P(Asp-Pr-OH)
16%	83	13	0.84	10.4
26%	77	20	0.74	11.4
31%	78	24	0.69	11.5
39%	74	29	0.61	12.3
54%	85	46	0.46	11.4
PEG-P(Asp-Bu)
13%	77	10	0.87	11.0
30%	82	25	0.70	11.0
35%	82	29	0.65	11.8
48%	84	40	0.52	11.3

^aDegree of polymerization determined by ¹H NMR (400 MHz).