Sequence-dependent cooperative interactions in A/T-containing oligo- and polydeoxyribonucleotides.

Area of Science:

• Molecular Biology
• Biochemistry
• Structural Biology

Background:

• Nonalternating adenine-thymine (A/T) sequences in deoxyribonucleic acid (DNA) exhibit unusual interaction properties.
• Understanding these properties is crucial for drug development and DNA structural studies.

Purpose of the Study:

• To investigate the length and sequence dependence of DNA-propidium interactions.
• To compare binding characteristics of alternating and nonalternating DNA oligomers.

Main Methods:

• Synthesis of DNA oligomers: d(A-T)6, dA10.dT10, and d(A6-T6).
• Spectrophotometric analysis of propidium binding to DNA oligomers.
• Low-temperature binding measurements and van't Hoff analysis.

Main Results:

• d(A-T)6 showed a higher binding constant for propidium than dA10.dT10.
• dA10.dT10 exhibited positive cooperativity and temperature-dependent binding constants, unlike d(A-T)6.
• Enthalpies for propidium binding were approximately -9 kcal/mol for alternating and +6 kcal/mol for nonalternating DNA.

Conclusions:

• DNA sequence and length critically affect propidium binding affinity and thermodynamics.
• Nonalternating sequences display unique binding behaviors, distinct from alternating sequences.
• These findings have implications for understanding DNA-drug interactions and sequence-specific DNA recognition.