Determining the binding mode and binding affinity constant of tyrosine kinase inhibitor PD153035 to DNA using optical tweezers

Accurately predicting binding affinity constant (K_A) is highly required to determine the binding energetics of the driving forces in drug-DNA interactions. Recently, PD153035, brominated anilinoquinazoline, has been reported to be not only a highly selective inhibitor of epidermal growth factor receptor but also a DNA intercalator. Here, we use a dual-trap optical tweezers to determining K_A for PD153035, where K_A is determined from the changes in B-form contour length (L) of PD153035-DNA complex. Here, L is fitted using a modified wormlike chain model. We found that a noticeable increment in L in 1mM sodium cacodylate was exhibited. Furthermore, our results showed that KA=1.18(±0.09)×10⁴ (1/M) at 23±0.5°C and the minimum distance between adjacent bound PD153035≈11bp. We anticipate that by using this approach we can determine the complete thermodynamic profiles due to the presence of DNA intercalators.