Visualization of enzymatic DNA extension by surface plasmon resonance imaging

The enzymatic extension of single-stranded DNA on a gold substrate was studied with surface plasmon resonance (SPR) imaging and atomic force microscopy. Extension of the DNA strands was carried out by TdT, which catalyzes the addition of different deoxynucleotidyl triphosphates (dNTPs) to the 3′-hydroxyl end of DNA. The extension rate of the DNA strands depended on the dNTPs, in the order of dATP ≈dTTP>dCTP>dGTP. The time-dependence of the DNA extension was imaged using SPR.