Selective growth inhibition of human malignant melanoma cells by syringic acid-derived proteasome inhibitors

Table 1 Virtual binding scores of syringic acid analogues and bortezomib

Compound	Total score	Crash	Polar
Bortezomib	8.50	−2.13	2.26
4	6.59	−1.76	1.93
3	6.58	−1.43	3.11
6	6.32	−1.31	2.07
5	6.06	−1.18	3.13
2	5.43	−0.86	3.05
Syringic acid	3.83	−1.52	1.45

Using SYBYL-X Surflex-Dock and the eukaryotic yeast 20S proteasome crystal structure (PDB code: 2 F16). Total score was expressed in –log (K_d) units to represent binding affinities. Crash is the degree of inappropriate penetration by the ligand into the protein and of interpenetration between ligand atoms that are separated by rotatable bonds. Polar score is the contribution of the polar non-hydrogen bonding interactions to the total score. The polar score may be useful for excluding docking results that make no hydrogen bonds.

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