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. 2010 Jan 11;285(12):9114–9123. doi: 10.1074/jbc.M109.044297

FIGURE 2.

FIGURE 2.

Differential stability of cyclic and linear NGR and isoDGR peptides. A, RP-HPLC of NGR-2C-TNF1–11 (5 μg) and NGR-2G-TNF1–11 (5 μg) after incubation at 37 °C in PBS. Dotted line, untreated peptide. Peak 1 corresponds to NGR-2C-TNF1–11; peak height was proportional to the loaded material within the range of 1–50 μg. B, RP-HPLC of NGR-2C after incubation at 37 °C in human serum. The peptide was added to human serum (500 μg/ml, final concentration) and incubated for the indicated time. The sample was then ultrafiltered through a 5 kDa cut-off ultrafilter (Vivaspin 500, Sartorius, Italy). The permeate (50 μl) was analyzed by RP-HPLC. Peak 1 corresponds to NGR-2C. C, stability of NGR-2C-TNF1–11, NGR-2G-TNF1–11, and NGR-2C after incubation at 37 °C or at 4 °C in PBS, HEPES buffer, water, or human serum, as determined by RP-HPLC. D and E, MALDI-TOF MS analysis of non-acetylated and acetylated NGR-2G, NGR-2C, isoDGR-2G, and isoDGR-2C after incubation at 37 °C for 0 and 8 days in PBS. +0, +1, −17, and −18 correspond to the difference between the found and the expected molecular masses in daltons.