Abstract
We report as a proof-of-concept the first application of circularly polarized luminescence (CPL) measured with a Raman optical activity (ROA) spectrometer to differentiate several DNA structures without need of sensitizing complexes. The ROA/CPL approach provides sufficiently high CPL intensity to use hydrated Eu3+ ions, thus avoiding DNA structural changes associated with binding of sensitizers and overcoming the sensitizer quenching issue. We showed that deoxyguanosine monophosphate (dGMP), single- and double-stranded DNA provide different CPL spectra, which could be used for their discrimination. Our results demonstrate that ROA/CPL method is a promising approach to measure CPL spectra of complex biomolecules when the use of sensitizers is not possible. The method can be extended to other biomolecules, such as proteins, lipids, sugars, etc.
Highlights
Application of circularly polarized luminescence (CPL) to DNA studies using commercial CPL spectrometers has been so far unsuccessful due to low signal intensity and quenching of the luminescence of sensitizing agents upon their binding to DNA10–12
In the present work we demonstrate a proof-of-concept that lanthanide CPL can be successfully measured for DNA using Raman optical activity (ROA) spectrometer (ROA/CPL method13)
We demonstrated that the ROA/CPL method enables sensitive probing of DNA structure using europium (III) aqua-ions, without the need of sensitizing agents
Summary
Application of CPL to DNA studies using commercial CPL spectrometers has been so far unsuccessful due to low signal intensity and quenching of the luminescence of sensitizing agents upon their binding to DNA10–12. In the present work we demonstrate a proof-of-concept that lanthanide CPL can be successfully measured for DNA using Raman optical activity (ROA) spectrometer (ROA/CPL method[13]). The method provides sufficiently high intensity of the CPL signal to avoid sensitizing complexes and use bare (hydrated-only) lanthanide ions at relatively low concentrations. Vibrational ROA signal (difference in scattering of the right and left circularly polarized light) is present in the spectrum as well, generally enabling measurement of four spectral types (TL, CPL, Raman and ROA spectra) in a single experiment, which makes the approach very attractive for structural studies of biomolecules. We plan to investigate the effect of DNA base content, conformation, number of strands, salt content, pH and temperature on the CPL signal
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