In a frequently applied method the exponent, n, of the distance R, of interacting molecules, appearing in the expression of the efficiency, f, of transfer, is determined from the slope of a straight line obtained by plotting In (f−1 −1) vs. In c/c0 (c and c0 are the concentration of the solution and a constant critical concentration characteristic of the interacting molecules and their environment, as defined in the Förster theory of transfer). The dependence of f on c is usually determined experimentally from the concentration quenching of fluorescence. From the theoretical quenching curve and the analytical expression for the slope, it is concluded that In (f−1 −1) vs. In c/c0 is not strictly linear, but a curve with slopes yielding exponents from n = −6−n = −3, in contrast to the fact that the interaction theoretically remains very weak (with n = −6). A correct exponent is obtained experimentally from the high-concentration part of the quenching curve or by using the theoretical dependence of the slope on the concentration in the case of very weak interactions. For strong interactions, In (f−1 −1) vs. In c/c0 is linear, and n = −3 in the whole concentration range. However, f is slightly volume-dependent.
ASJC Scopus subject areas
- Statistics and Probability
- Modelling and Simulation
- Biochemistry, Genetics and Molecular Biology(all)
- Immunology and Microbiology(all)
- Agricultural and Biological Sciences(all)
- Applied Mathematics