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Porphyrin binding to DNA investigated by cyclodextrin supramolecular system
Xiao-Ping Wang1, Jing-Hao Pan, Xiao-Dong Yang
1Chemistry Department of Shanxi University, Taiyuan 030006, People's Republic of China.
Analytical and Bioanalytical Chemistry
|October 10, 2002
Summary
The study reveals that meso-tetrakis-(4-N-trimethylaminobenzyl)porphyrin (TAPP) binds to DNA via electrostatic interactions, not intercalation. Anionic cyclodextrins inhibit this binding by competing for TAPP
Area of Science:
- Biochemistry
- Supramolecular Chemistry
- Molecular Biology
Background:
- Meso-tetrakis-(4-N-trimethylaminobenzyl)porphyrin (TAPP) is a positively charged porphyrin derivative.
- Cyclodextrins (CDs) are cyclic oligosaccharides capable of forming inclusion complexes.
- Understanding the interaction of porphyrins with DNA is crucial for developing novel therapeutic and diagnostic agents.
Purpose of the Study:
- To investigate the binding mode of TAPP with DNA using a cyclodextrin-porphyrin supramolecular system.
- To elucidate the role of cyclodextrins, particularly anionic and neutral derivatives, in modulating TAPP-DNA interactions.
- To determine the specific binding mechanism and stoichiometry between TAPP and DNA.
Main Methods:
- Nuclear Magnetic Resonance (NMR) spectroscopy ((1)H-NMR) was used to study the inclusion complex formation between TAPP and cyclodextrins.
- Spectroscopic techniques were employed to investigate the binding of TAPP with DNA in the presence and absence of cyclodextrins.
- Computational modeling was utilized to propose a binding structure for the TAPP-DNA complex.
Main Results:
- The hydrophobic segment of TAPP enters the cyclodextrin cavity, indicating that the porphyrin's hydrophobic part is not involved in DNA binding.
- Anionic sulfobutyl-beta-cyclodextrin (SB-beta-CD) inhibits TAPP-DNA binding by competing for electrostatic interactions with TAPP, while neutral CDs have no effect.
- Experimental data strongly support an electrostatic binding model between TAPP and DNA, with evidence of two binding sites per TAPP-DNA complex.
Conclusions:
- The binding of TAPP to DNA is primarily driven by electrostatic attraction, not intercalation or groove binding.
- Anionic cyclodextrins can effectively modulate TAPP-DNA interactions by disrupting the electrostatic binding.
- A suprahelical DNA structure is proposed as a possible binding site for the TAPP-DNA complex, consistent with literature findings.