Table 1. Intracellular concentrations (μM) ^a of copper and various ligands ^b .

	HUVEC		OVCAR5
	[Ligand]	[Cu]	[Ligand]	[Cu]
Control 1 c		22 ± 2		23 ± 1
Control 2 d		46 ± 3		95 ± 2
1/CuSO4	1.0 ± 0.1	52 ± 3	4.3 ± 0.2	104 ± 2
2/CuSO4	10.8 ± 0.3	69 ± 4	8.6 ± 0.2	139 ± 3
3/CuSO4	32.9 ± 0.4	86 ± 3	68.8 ± 1.8	163 ± 3

^aDerived from the total uptake (measured by LC-MS/MS) divided by the number of cells and the cell volume assuming to be 1.7 picoliters.³⁸

^bAfter incubation in 100 μM CuSO₄, 200 μM ligand, 500 μM NaAsc in 10/90 (v/v) methionine-free DMEM/PBS for 10 minutes, the same conditions used for the intracellular CuAAC reaction but without the azide.

^cControl 1 was performed without both ligand and CuSO₄.

^dControl 2 was performed without the ligand. For deriving the error propagated from the measured amounts of ligand/copper and cell counting, see ESI†.