Albany 2001

category image Biomolecular
SUNY at Albany
June 19-23, 2001

DNA Condensation Studied by Vibrational Circular Dichroism (VCD) and IR Spectroscopy

The present study deals with an investigation of metal ion induced DNA condensation by means of Vibrational Circular Dichroism spectroscopy (VCD). It has been known for a long time that at certain conditions so called psi-type DNA condensation occurs, which can be easily determined by Electronic CD (ECD) due to appearance of large characteristic ECD spectra (1). The main drawback of the ECD technique in this case is its inability to determine secondary structure of the DNA inside the condensed particles.

A drastic intensity increase of VCD spectra as well as several other characteristic changes similar to that observed in ECD occurred during DNA condensation induced by Cr(3+) ions, indicating VCD's ability to detect psi-type DNA condensation. In contrast to ECD, the combination of VCD and IR absorption spectroscopy not only enabled the observation of DNA condensation, but also the determination of DNA secondary structure upon condensation in the same experiment.

Divalent metal ions are known to induce DNA aggregation at increased temperatures. Some authors have suggested the additional possibility of DNA condensation in these conditions (2). The application of VCD to DNA complexes with Mn(2+) ions at different temperatures confirmed that these ions indeed are capable of inducing DNA condensation at elevated temperatures. Furthermore, VCD was able to distinguish between DNA condensation and aggregation, which is hardly possible with other techniques.

References and Footnotes

  1. Jordan, C.F., Lerman, L.S. & Venable, J.H. (1972) Nature New Biol. 236, 67-70.
  2. Knoll, D.A., Fried, M.G. &Bloomfield, V.A. (1988) in Structure & Expression. Volume 2- DNA and Its Drug Complexes, Sarma, R.H. & Sarma, M.H., Eds., Adenine Press, pp. 123-145.

V. Andrushchenko (1), J.H. van de Sande (2) and H.Wieser (1)

(1)Department of Chemistry, University of Calgary, Calgary, AB, T2N 1N4 Canada, Phone: (403)-220-3231; Fax: (403)-289-9488; email: vandrush@ucalgary.ca (2)Department of Medical Biochemistry, Faculty of Medicine, University of Calgary, Calgary, AB, T2N 1N4 Canada