Association of short DNA fragments: Steady state fluorescence polarization study
✍ Scribed by Torleif Härd; David R. Kearns
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1986
- Tongue
- English
- Weight
- 654 KB
- Volume
- 25
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
We have studied aggregation/association of monodisperse DNA fragments (ranging from 30-90 base pairs) by steady-state fluorescence polarization of intercalculated ethidium. The method of excitation a t different wavelengths in the ethidium absorption spectrum provides information about anisotropic twisting and tumbling mobility of the fragments. We find that end-over-end tumbling rather than axial spinning and internal twisting motions are affected by aggregation,' association. The critical concentration for observing the effects of intermolecular interactions is approximately 5 mg DNA/mL a t room temperature, independent of fragment length. Association is favored by low temperature and high ( > 10 m M ) concentration of Mg2+. From temperatureand salt-dependence experiments we infer that the "aggregates" are similar to those observed in a recently discovered DNA sol-gel transition [M. G . Fried and V. A. Bloomfield (1984) Biopolymers 23, 2141-21551. We also discuss possible arrangements of the fragments within the aggregates and their possible relation to formation of DNA liquid crystals.