Figure 5
Panel A: Release of R.I.CK(fluorescein)-Tat9 from PEG10 K-[(R.I.CK(fluorescein)-Tat9]8 in PBS (pH 7.4) (■), in plasma (▲) or PBS (pH 7.4) with 5μM GSH (▼) at 37°C respectively, using fluorescence detection at excitation wavelength 485 nm and emission wavelength 535 nm. The concentrations of the bioconjugates were determined from fluorescence calibration curves that were established in the same media. All measurements were done in duplicates. Panel B: Plot of ln(bioconjugate)t versus incubation time (t) of the PEG- [R.I.CK(fluorescein)-Tat9]8 in PBS (pH 7.4) (■), in plasma (▲) or PBS (pH 7.4) with 5 μM GSH (▼) at 37°C respectively. The rate constant (k) is the slope of this linear plot. The half-lives (t1/2) for the thioether bond cleavage were calculated using the relation t1/2 = 0.693/k.