Dynamics of the electron transfer reaction between an oxazine dye and DNA oligonucleotides monitored on the single-molecule level

Single-molecule spectroscopy in water has been investigated by monitoring the dynamical behaviour of the electron transfer reaction between guanosine-containing oligonucleotides and the covalently attached oxazine dye MR121, using diode laser based far-field fluorescence microscopy. In this system, each oligonucleotide molecule exhibits multiexponential electron transfer kinetics. The influence of the guanosine position on the degree of quenching is shown using different oligonucleotide sequences. The dynamical behaviour of conformational transitions between various states with different electron transfer efficiency is monitored by time-resolved fluorescence spectroscopy on the μs- and ms-time scales. In addition, guanosine specific on/off blinking of individual labeled oligonucleotide molecules in aqueous solution is shown.