Fluorescence and photobleaching studies of methylene blue binding to DNA

Bryant S. Fujimoto; James B. Clendenning; Jeffrey J. Delrow; Patrick J. Heath; J. Michael Schurr

doi:10.1117/12.182780

17 August 1994 Fluorescence and photobleaching studies of methylene blue binding to DNA

Bryant S. Fujimoto, James B. Clendenning, Jeffrey J. Delrow, Patrick J. Heath, J. Michael Schurr

Proceedings Volume 2137, Time-Resolved Laser Spectroscopy in Biochemistry IV; (1994) https://doi.org/10.1117/12.182780
Event: OE/LASE '94, 1994, Los Angeles, CA, United States

Abstract

Complexes of methylene blue with DNA are characterized by time- resolved fluorescence spectroscopy and transient photobleaching methods. At least four, and probably five, spectroscopically distinct binding sites have been identified. Three of these (components 1, 2, and 3B) dominate the fluorescence decay at low ionic strength and have fluorescence lifetimes significantly different from that of the free dye. With increasing ionic strength a fourth component (3A) appears at the expense of components 1 and 3B. Component 3A exhibits two subcomponents with different degrees of shielding from O₂ quenching of its triplet state. The relative amplitudes of the components at low ionic strength are strongly dependent on the composition of the DNA, and independent of superhelix density. Hence, it is inferred that components 1, 2, and 3B represent binding to different base pair steps, and that all of these components represent intercalation sites that unwind the DNA to the same degree. Component 3A is apparently not intercalated. From plots of the relative photobleach amplitudes versus the relative fluorescence intensities, we infer that the triplet yield and photobleach amplitude are dominated by components 3A and/or 3B under nearly all conditions. Our results are used to discuss the suitability of methylene blue as the extrinsic probe in transient photodichroism experiments.

Citation Download Citation

Bryant S. Fujimoto, James B. Clendenning, Jeffrey J. Delrow, Patrick J. Heath, and J. Michael Schurr "Fluorescence and photobleaching studies of methylene blue binding to DNA", Proc. SPIE 2137, Time-Resolved Laser Spectroscopy in Biochemistry IV, (17 August 1994); https://doi.org/10.1117/12.182780

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available