This tutorial review summarizes the most important results and developments in the field of polymer science by means of single molecule fluorescence spectroscopy (SMFS) at ambient temperatures. A broad range of topics will be addressed and it will be discussed which single molecule methods are suitable to get the maximum amount of information about polymer structure, polymer dynamics and the photophysics of incorporated or embedded dye molecules. In particular, we will report on the use of polymer films for immobilization of molecules, the visualization of dynamics near the glass transition temperature T_g, the reptation of polymer chains, the conformation adopted by polymer chains and the in situ observation of the polymerization reaction itself.

Fluorescence correlation spectroscopy (FCS) investigations to study the structure and dynamics in polymer systems are reviewed and discussed.

Electroporation is a physical method of transferring molecules into cells and tissues. It takes advantage of the transient permeabilization of the cell membrane induced by electric field pulses, which gives hydrophilic molecules access to the cytoplasm. This method offers high transfer efficiency for small molecules that freely diffuse through electrically permeabilized membranes. Larger molecules, such as plasmid DNA, face several barriers (plasma membrane, cytoplasmic crowding, and nuclear envelope), which reduce transfection efficiency and engender a complex mechanism of transfer. Our work provides insight into the way electrotransferred DNA crosses the cytoplasm to reach the nucleus. For this purpose, single-particle tracking experiments of fluorescently labeled DNA were performed. Investigations were focused on the involvement of the cytoskeleton using drugs disrupting or stabilizing actin and tubulin filaments as the two relevant cellular networks for particle transport. The analysis of 315 movies (~4,000 trajectories) reveals that DNA is actively transported through the cytoskeleton. The large number of events allows a statistical quantification of the DNA motion kinetics inside the cell. Disruption of both filament types reduces occurrence and velocities of active transport and displacements of DNA particles. Interestingly, stabilization of both networks does not enhance DNA transport.