Conformational fluctuations in single DNA molecules.
Measurement of fluorescent lifetimes of dye-tagged DNA molecules reveal the existence of different conformations. Conformational fluctuations observed by fluorescence correlation spectroscopy give rise to a relaxation behavior that is described by "stretched" exponentials and indicates the presence of a distribution of transition rates between two conformations. Whether this is an inhomogeneous distribution, where each molecule contributes with its own reaction rate to the overall distribution, or a homogeneous distribution, where the reaction rate of each molecule is time-dependent, is not yet known. We used a tetramethylrhodamine-linked 217-bp DNA oligonucleotide as a probe for conformational fluctuations. Fluorescence fluctuations from single DNA molecules attached to a streptavidin-coated surface directly show the transitions between two conformational states. The conformational fluctuations typical for single molecules are similar to those seen in single ion channels in cell membranes.
Wennmalm
S
S
Department of Medical Biophysics, Karolinska Institute, S-171 77, Stockholm, Sweden.
Edman
L
L
Rigler
R
R
D004247:DNA / Q000737:chemistry*; D008956:Models, Chemical; D009690:Nucleic Acid Conformation; D013050:Spectrometry, Fluorescence
D004247:DNA