期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2004
卷号：101
期号：10
页码：3426-3431
DOI：10.1073/pnas.0400591101
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Circular dichroism is commonly used to investigate the conformations of nucleic acids. However, many biochemical processes implicate conformational changes of particular nucleotide residues within DNA or RNA that cannot be studied by this method, because the CD of these residues is buried in the total signal of the polynucleotide. Here, we report a method to study local conformations of DNA or RNA that is based on the use of the CD of 2-aminopurine (AP) residues as a probe. AP is readily incorporated into DNA in place of adenine and does not significantly alter DNA structure. Unlike adenine, AP is fluorescent and this property has been used for many years to investigate local nucleic acid structure. We show here that the CD spectrum of AP dinucleotide, (AP)2, exhibits a positive CD band at 326 nm, a spectral region in which nucleic acids (and proteins) do not absorb. Our results show that the bases of (AP)2 are stacked in a right-handed helical conformation. A low-energy CD band is also observed when this nucleotide dimer is incorporated into double-stranded DNA. Control experiments show that this signal comes from the stacking of adjacent AP residues. We have used this CD signal to provide information about the conformation of the AP dinucleotide at a defined position within single- and double-stranded nucleic acids.
