TY - JOUR
T1 - Steady-State and Time-Resolved Studies into the Origin of the Intrinsic Fluorescence of G-Quadruplexes
AU - Sherlock, Madeline E.
AU - Rumble, Christopher A.
AU - Kwok, Chun Kit
AU - Breffke, Jens
AU - Maroncelli, Mark
AU - Bevilacqua, Philip C.
N1 - Funding Information:
We thank Dr. Dan Sykes for assistance with SEC studies. This study was supported by Human Frontier Science Program (HFSP) [grant RGP0002/2009-C] to P.C.B. C.R. and J.B. were upported by the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences of the U.S. Department of Energy through Grant DE-SC0008640.
Publisher Copyright:
© 2016 American Chemical Society.
PY - 2016/6/16
Y1 - 2016/6/16
N2 - Stretches of guanines in DNA and RNA can fold into guanine quadruplex structures (GQSs). These structures protect telomeres in DNA and regulate gene expression in RNA. GQSs have an intrinsic fluorescence that is sensitive to different parameters, including loop sequence and length. However, the dependence of GQS fluorescence on solution and sequence parameters and the origin of this fluorescence are poorly understood. Herein we examine effects of dangling nucleotides and cosolute conditions on GQS fluorescence using both steady-state and time-resolved fluorescence spectroscopy. The quantum yield of dGGGTGGGTGGGTGGG, termed "dG3T", is found to be modest at ∼2 × 10-3. Nevertheless, dG3T and its variants are significantly brighter than the common nucleic acid fluorophore 2-aminopurine (2AP) largely due to their sizable extinction coefficients. Dangling 5′-end nucleotides generally reduce emission and blue-shift the resultant spectrum, whereas dangling 3′-end nucleotides slightly enhance fluorescence, particularly on the red side of the emission band. Time-resolved fluorescence decays are broadly distributed in time and require three exponential components for accurate fits. Time-resolved emission spectra suggest the presence of two emitting populations centered at ∼330 and ∼390 nm, with the redder component being a well-defined long-lived (∼1 ns) entity. Insights into GQS fluorescence obtained here should be useful in designing brighter intrinsic RNA and DNA quadruplexes for use in label-free biotechnological applications.
AB - Stretches of guanines in DNA and RNA can fold into guanine quadruplex structures (GQSs). These structures protect telomeres in DNA and regulate gene expression in RNA. GQSs have an intrinsic fluorescence that is sensitive to different parameters, including loop sequence and length. However, the dependence of GQS fluorescence on solution and sequence parameters and the origin of this fluorescence are poorly understood. Herein we examine effects of dangling nucleotides and cosolute conditions on GQS fluorescence using both steady-state and time-resolved fluorescence spectroscopy. The quantum yield of dGGGTGGGTGGGTGGG, termed "dG3T", is found to be modest at ∼2 × 10-3. Nevertheless, dG3T and its variants are significantly brighter than the common nucleic acid fluorophore 2-aminopurine (2AP) largely due to their sizable extinction coefficients. Dangling 5′-end nucleotides generally reduce emission and blue-shift the resultant spectrum, whereas dangling 3′-end nucleotides slightly enhance fluorescence, particularly on the red side of the emission band. Time-resolved fluorescence decays are broadly distributed in time and require three exponential components for accurate fits. Time-resolved emission spectra suggest the presence of two emitting populations centered at ∼330 and ∼390 nm, with the redder component being a well-defined long-lived (∼1 ns) entity. Insights into GQS fluorescence obtained here should be useful in designing brighter intrinsic RNA and DNA quadruplexes for use in label-free biotechnological applications.
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U2 - 10.1021/acs.jpcb.6b03790
DO - 10.1021/acs.jpcb.6b03790
M3 - Article
C2 - 27267433
AN - SCOPUS:84975230593
SN - 1520-6106
VL - 120
SP - 5146
EP - 5158
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 23
ER -