Effect of [Na+] on [99mTc(CO)
]+radiolabelling of His-tagged proteins. Labelling efficiencies (n = 3) of (a) rCR2, (b) α-CD33 scFv, (c) α-PSMA scFv and (d) α-VCAM-1 scFv proteins were determined at 5, 15, 30, 60, 90 and 120 min and represented as a percentage of incorporated [99mTc(CO)3]+. Error bars represent the standard deviation of the mean of the triplicate. Where error bars are not visible, they are smaller than the data points.