title: Associated Anisotropy Decays of Ethidium Bromide Interacting with DNA.
abstract: Ethidium Bromide (EB) is a commonly used dye in a deoxyribonucleic acid (DNA) study. Upon an intercalation, this dye significantly increases its brightness and fluorescence lifetime. In this report we have studied the time-resolved fluorescence properties of EB existing simultaneously in free and DNA-bound forms in the solution. Fluorescence intensity decays were fitted globally to a double exponential model with lifetimes corresponding to free (1.6ns) and bound (22ns) forms, and molar fractions were determined for all used solutions. Anisotropy decays displayed characteristic time dependence with an initial rapid decline followed by recovery and slow decay. The short-lived fraction associated with free EB molecules decreases faster than long-lived fraction associated with EB bound to DNA. Consequently, contribution from fast rotation leads to initial rapid decay in anisotropy. On the other hand bound fraction, due to slow rotation helps recover anisotropy in time. This effect of associated anisotropy decays in systems such as EB free/EB-DNA is clearly visible in a wide range of concentrations, and should be taken into account in polarization assays and biomolecule dynamics studies.
authors.affiliation: Department of Cell Biology and Immunology, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX 76107, USA.
authors.forename: Rahul
authors.initials: R
authors.lastname: Chib
authors.affiliation: Department of Cell Biology and Immunology, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX 76107, USA.
authors.forename: Sangram
authors.initials: S
authors.lastname: Raut
authors.affiliation: Department of Cell Biology and Immunology, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX 76107, USA.
authors.forename: Sarika
authors.initials: S
authors.lastname: Sabnis
authors.affiliation: Department of Cell Biology and Immunology, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX 76107, USA.
authors.forename: Preeti
authors.initials: P
authors.lastname: Singhal
authors.affiliation: Department of Cell Biology and Immunology, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX 76107, USA ; Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX, 76129, USA.
authors.forename: Zygmunt
authors.initials: Z
authors.lastname: Gryczynski
authors.affiliation: Department of Cell Biology and Immunology, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX 76107, USA.
authors.forename: Ignacy
authors.initials: I
authors.lastname: Gryczynski
keywords: Associated anisotropy decays; Ethidium Bromide and DNA fluorescence