Conformation of DNA in periodic temperature gradient created by plasmonic heating

Different molecules in mixed solutions can be separated from each other along a temperature gradient. This phenomenon, so-called Soret effect, is quite important for molecular manipulation in various research fields. Among various techniques, plasmonic heating from periodic metal domains is one of the effective ways to create a periodic temperature gradient for observation of the Soret effect. In this work, we utilized the plasmonic heating from periodic silver (Ag) domains under emission of blue light (400 – 440 nm) to create the periodic temperature gradient (with a large amplitude of ~ 0.5 K/mm), thereby attempting to observe the Soret effect of DNA mixed in polyethylene glycol (PEG) solutions. The DNA molecules, labeled with fluorescent dyes, were concentrated in high temperature zones, confirming the positive Soret effect. In addition, for large DNA molecules (~ 166 Kbp), the conformation appeared to be distorted possibly because of the microscopic Soret effect within the molecule. Details of this observation will be discussed on site.