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Sequence selectivity of azinomycin B in DNA alkylation and cross-linking: a QM/MM study

Dhurairajan Senthilnathan1, Anbarasan Kalaiselvan, Ponnambalam Venuvanalingam

  • 1School of Chemistry, Bharathidasan University, Tiruchirappalli, 620024, India.

Journal of Molecular Modeling
|August 30, 2012
PubMed

Insights

Azinomycin B, an antitumor drug, alkylates DNA's guanine base, blocking tumor growth. Computational modeling revealed a two-step mechanism, with mono-alkylation kinetically controlled and bis-alkylation thermodynamically controlled.

Area of Science:

  • Computational Chemistry
  • Medicinal Chemistry
  • Molecular Biology

Background:

  • Azinomycin B is a known antitumor agent that functions by cross-linking DNA.
  • The precise mechanism and selectivity of this DNA alkylation are not fully understood.
  • Understanding this process is crucial for developing more effective cancer therapies.

Purpose of the Study:

  • To elucidate the reaction mechanism and sequence selectivity of Azinomycin B's DNA alkylation.
  • To investigate the roles of the aziridine and epoxide rings in the alkylation process.
  • To determine the kinetic and thermodynamic control of mono- and bis-alkylation.

Main Methods:

  • Utilized the ONIOM (B3LYP/6-31+g(d):UFF) method for theoretical modeling.
  • Validated ONIOM results with full quantum mechanics calculations.
  • Incorporated solvent effects using polarized continuum model calculations.

Main Results:

  • Guanine was identified as the most reactive purine base towards Azinomycin B.
  • Alkylation occurs sequentially: first the aziridine ring at C10, then the epoxide ring at C21.
  • Mono-alkylation is kinetically controlled, while bis-alkylation is thermodynamically controlled.
  • Solvent effects showed minimal impact on the reaction mechanism compared to gas-phase calculations.

Conclusions:

  • The study provides a detailed computational understanding of Azinomycin B's DNA alkylation mechanism.
  • The findings highlight the differential kinetic and thermodynamic control governing mono- and bis-alkylation.
  • This mechanistic insight can inform the design of novel antitumor agents targeting DNA.

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