In situ measurements of the dynamics of single giant DNA molecules at the toluene-trioctylamine/water interface by total internal reflection fluorescence microscopy.

The dynamics of single giant deoxyribonucleic acid (T4GT7DNA, 165 600 base pairs) molecules was examined near and at the toluene/water, toluene-trioctylamine mixtures/water, and trioctylamine/water interfaces by total internal reflection fluorescence microscopy. The results were considerably affected by the trioctylamine content. With pure toluene or mixtures of lower trioctylamine volume contents (%VA), the randomly coiled DNA molecules diffused to near the interfaces. With mixtures of higher %VA (9 and 50%), the DNA molecules were stretched and adsorbed at the interfaces. There are a large number of anionic phosphate groups ((-O)2PO2-) in the DNA molecule that have an electrostatic affinity to protonated trioctylamine existing at the interface. In the case of pure trioctylamine, globular DNA molecules were adsorbed at the interface and also existed in the aqueous phase.