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Fluorescence‐detected circular dichroism of dinucleoside phosphates. A study of solution conformations and the two‐state model
Author(s) -
Reich Charles,
Tinoco Ignacio
Publication year - 1980
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1980.360190409
Subject(s) - chemistry , circular dichroism , fluorescence , stacking , dimer , crystallography , molecule , absorption (acoustics) , organic chemistry , materials science , physics , quantum mechanics , composite material
Three fluorescent dinucleoside phosphates containing 1, N 6 ‐ethenoadenosine (εA), εA p εA, εA p εC, and εA p U were studied using fluorescence‐detected circular dichroism (FDCD), circular dichroism (CD), and absorption measurements. The FDCD data indicate that εA p εC and εA p U can be described as two‐state systems consisting of a fluorescent species and a stacked, nonfluorescent species. Thermodynamic stacking parameters are calculated for these molecules using the van't Hoff equation. εA p εA is found to be a more complicated system with a fluorescent CD which is different in shape, but comparable in magnitude, to the conventional CD of the dimer. This molecule, unlike the other two dinucleoside phosphates, cannot be characterized as a two‐state system; it is described as consisting of at least three states at temperatures above 35°C. The CD data were subjected to a linear analysis in order to determine the minimum number of states present. In agreement with the FDCD data, εA p εC and εA p U are found to consist of a minimum of two states, while εA p εA is indicated to have at least three. The more complicated behavior of the latter dimer is also indicated by the values of the unstacked CD obtained in the van't Hoff analysis.