Table 2.

Correlation of linker structure with IC₅₀ values for c-Src inhibition

Entry	Compound	Linker	c-Src IC50, μM
1	[90, 273, n = 2]		0.064  ± 0.038
2	[90, 273, n = 3]		1.1  ± 0.2
3	[90, 273, n = 4]		6.5  ± 3.0
4	[90, 273, n = 5]		6.5  ± 0.8
5	[90, 273, n = 6]		5.3  ± 2.1
6	[90, 273, cis]		1.2  ± 0.6
7	[90, 273, trans (1R,2R)]		0.62  ± 0.20
8	[90, 273, trans (1S,2S)]		1.8  ± 0.7

Assays were performed with purified material. Enzyme inhibition was expressed as the IC₅₀, the concentration of inhibitor required for half-maximal inhibition of phosphorylation of the biotinylated tyrosine kinase peptide substrate (biotin-KVEKIGEGTYGVVYK) at an ATP concentration of 125 μM. For each IC₅₀ determination assays were performed in duplicate or triplicate at six inhibitor concentrations. For assay calibration, the IC₅₀ of the known inhibitor PP1 was determined to be 0.32 μM (literature value = 0.17 μM) (32).