Actinomycin D and 7-aminoactinomycin D binding to single-stranded DNA

Area of Science:

• Molecular Biology
• Biochemistry
• Biophysical Chemistry

Background:

• Actinomycin D and 7-aminoactinomycin D are known RNA polymerase inhibitors.
• Their interaction with double-stranded DNA is well-documented.
• The binding of these drugs to single-stranded DNA has not been extensively studied.

Purpose of the Study:

• To investigate the binding of actinomycin D and 7-aminoactinomycin D to single-stranded DNA.
• To characterize the biophysical properties of these interactions.
• To explore the potential of these interactions for DNA detection.

Main Methods:

• UV-Vis absorption spectroscopy
• Fluorescence spectroscopy (emission, anisotropy, lifetime)
• Polyacrylamide gel electrophoresis
• Binding affinity determination

Main Results:

• Actinomycin D and 7-aminoactinomycin D bind to specific guanine-rich sequences in single-stranded DNA.
• Binding induces hypochromic UV absorption changes.
• 7-aminoactinomycin D exhibits a dramatic fluorescence enhancement (37-fold) upon binding to single-stranded DNA.
• Spectral shifts (40 nm hypsochromic) and changes in fluorescence lifetime (increase in 2-ns component) were observed.
• The drug-DNA complex is visualized via fluorescence in polyacrylamide gels.
• Association constants range from 2.0 x 10^6 to 1.1 x 10^7 M^-1.

Conclusions:

• 7-aminoactinomycin D binding to single-stranded DNA is sequence-specific and results in significant fluorescence changes.
• These properties can be utilized for visualizing and characterizing DNA-drug interactions.
• The study provides a foundation for using these compounds as fluorescent probes for single-stranded DNA.