DYNAMICS OF THE ELECTRON-TRANSFER REACTION BETWEEN AN OXAZINE DYE ANDDNA OLIGONUCLEOTIDES MONITORED ON THE SINGLE-MOLECULE LEVEL

Single-molecule spectroscopy in water has been investigated by monitor ing the dynamical behaviour of the electron transfer reaction between guanosine-containing oligonucleotides and the covalently attached oxaz ine dye MR121, using diode laser based far-field fluorescence microsco py. In this system, each oligonucleotide molecule exhibits multiexpone ntial electron transfer kinetics. The influence of the guanosine posit ion on the degree of quenching is shown using different oligonucleotid e sequences. The dynamical behaviour of conformational transitions bet ween various states with different electron transfer efficiency is mon itored by time-resolved fluorescence spectroscopy on the mu s- and ms- time scales. In addition, guanosine specific on/off blinking of indivi dual labeled oligonucleotide molecules in aqueous solution is shown. ( C) 1998 Elsevier Science B.V.