Excitation energy transfer in DNA: Duplex melting and transfer from normal bases to 2-aminopurine

• Published in: Biochemistry (Easton) 1993-11, Vol.32 (45), p.12090-12095
• Main Authors: Nordlund, Thomas M, Xu, Daguang, Evans, Kervin O
• Format: Article
• Language: English
• Subjects: 2-Aminopurine - chemistry; Analytical, structural and metabolic biochemistry; Base Sequence; Biological and medical sciences; DNA - chemistry; Dna, deoxyribonucleoproteins; Fundamental and applied biological sciences. Psychology; Molecular Sequence Data; Nucleic Acid Denaturation; Nucleic acids; Oligodeoxyribonucleotides; Spectrometry, Fluorescence; Spectrophotometry, Ultraviolet; Temperature; Thermodynamics
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00096a020

Absorption and fluorescence excitation and emission spectra of the B DNA duplex decamer d[CTGA(2AP)TTCAG]2, where emission from the 2AP (2-aminopurine) base dominates, have been measured as a function of temperature. A low-temperature excitation band in the 260-270-nm region disappears near the duplex melting temperature, Tm = 27 degrees C, but then reappears at higher temperatures. Singlet-singlet energy transfer thus occurs between the normal DNA bases and the 2AP base in the B-helical conformation and to a lesser extent in the structurally-mobile melted conformation. The measured efficiency of transfer is 4-5% at 4 degrees C, near 0 at 30 degrees C, and rises again to 1% at 48 degrees C. Nearest-neighbor-only singlet transfer is likely. Such transfer does not offer a likely explanation for UV damage distributions in DNA.