Decrease in the absorbance of PEG<sub>40</sub>-CONH-(CH<sub>2</sub>)<sub>5</sub>-CONH-(CH<sub>2</sub>)<sub>6</sub>-NHCO-MTX with time during dialysis against 1mM HCl.

<p>PEG<sub>40</sub>-CONH-(CH<sub>2</sub>)<sub>5</sub>-CONH-(CH<sub>2</sub>)<sub>6</sub>-NHCO-MTX and PEG<sub>40</sub>-CONH-(CH<sub>2</sub>)<sub>6</sub>-NHCO-MTX (0.2 μmole/ml of each) were dialyzed against one liter of 1mM HCl (pH 3.0). At the indicated time points, 30 μl aliquots were withdrawn from the dialysis tube, diluted 20 folds and their absorbance at 305 nm was monitored. Data are presented as mean±STDEV (n = 3).</p>