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. 2013 Apr 11;8(4):e60649. doi: 10.1371/journal.pone.0060649

Figure 1. Inhibition of 20 S proteasome activity by homopiperazine derivatives.

Figure 1

A. Purified erythrocyte-derived 20 S proteasome was incubated in the absence (control) or presence of the indicated HPDS at 5 µM. Chymotrypsin-like, caspase-like and trypsin-like activities were determined by measuring fluorescence generated from the cleavage of specific substrates. Results are represented as relative fluorescence units (RFU) with control set at 100%. The means ± S.D. (bars) of three independent experiments are shown. P-values were calculated by one-way ANOVA with the Student-Newman-Keuls multiple comparisons test. Asterisks indicate p<0.05 against corresponding controls. B. RPMI8226 cells were treated with or without 5 µM HPDs, and analyzed for proteolytic activities as described above. C. RPMI8226 cells were cultured in the absence (control) or presence of 10 µM HPDs for 24 hours, and subjected to immunoblotting for ubiquitinated proteins and GAPDH (internal control).