Showing papers by "Seog K. Kim published in 1990"
01 Jan 1990
TL;DR: The present study of a classical non—intercalator, DAPI (4‘,6—diamidino—2—phenylindole), offers several surprising features, including the existence of two “binding sites” on DNA, one with an extremely low density as evidenced from CD, which is surprisingly enough also found with the homopolymer poly(dA—dT).
Abstract: Attention is focused on flow linear dichroism (FLD) measured with phase—modulation technique as a simplistic tool for detecting and characterizing DNA drug interactions. FLD combined with DNA—induced circular dichroism (CD), and in some instances fluorescence polarization anisotropy (FPA), has thus for a number of intercalators and non—intercalators provided important information about effective binding geometries and orientational dynamics under varying solution and binding conditions. The present study of a classical non—intercalator, DAPI (4‘,6—diamidino—2—phenylindole), offers several surprising features. FLD supports that DAPI binds in the minor groove of DNA and poly(dA—dT), but suggests that it may be intercalated in poly(dG—dC), albeit fluorescence quenching by iodide ion contradicts classical intercalation. The existence of two “binding sites” on DNA, one with an extremely low density as evidenced from CD, is surprisingly enough also found with the homopolymer poly(dA—dT). Three possible explanations for this observation are discussed: 1) the low—density site may be a “transient site” owing to DNA conformational dynamics, 2) the second site may reflect interacting DAPI monomers or 3) be an effect of a small allosteric conformational change in DNA. However, first at very high degrees of occupancy exciton DAPI—DAPI interaction indicates the presence of true dimers. Results from molecular mechanics calculations are in agreement with that different binding modes are preferred in poly(dG—dC) and poly(dA—dT) but give no indication as to the origin of two DAPI binding sites in the latter.
11 citations