EXCITED STATES OF DNA and ITS COMPONENTS AT ROOM TEMPERATURE–V. SPECTRAL, POLARIZATION and QUANTUM YIELD STUDIES OF CYTIDYLYL‐(3‘,5’)‐ADENOSINE

Abstract

Abstract— The corrected normalized emission spectrum, quantum yield, and emission anisotropy are reported for partially‐stacked CpA excited at 266 nm. Utilizing parameters determined separately for cytidine and AMP, the emission spectrum of CpA is quantitatively resolved into components characteristic of the two monomers plus a red shifted emission characteristic of complex formation. The results fit accurately to a simple stacking model in which monomer‐like fluorescence originates only from the unstacked fraction and “complex” fluorescence from the stacked fraction. It is shown that the stacked fraction absorbs in a manner qualitatively distinct from the unstacked fraction and the “complex” emission is really the excited state of a ground state complex. This emission, which peaks at 440 nm and contains at least two species can be resolved into three Gaussian components. It is suggested that the emitting species may originate in distinct stacked conformations.

Ultrafast photo-initiated molecular quantum dynamics in the DNA dinucleotide d(ApG) revealed by broadband transient absorption spectroscopy

“…The additional phosphate group at the 5 0 -end of d(pApG) compared to d(ApG) is not expected to have any signicant effect here. 1, [40][41][42][43][44][45][46] 3 Results…”

“…3b, inset). The tted d(ApG) uorescence lifetimes in this 'excimer' emission region [40][41][42][43][44][45][46] exponential with s 0 FL2 ¼ 0.86 AE 0.10 ps. These lifetimes for the monomers are in good agreement with available literature data.…”

“…Experimental section), the extra phosphate of d(pApG) compared to d(ApG) does not alter the relevant dual fluorescence properties of the dinucleotide. 1, [40][41][42][43][44][45][46] observed for the adenine dinucleotide d(ApA), where the excimer state revealed itself by its exceptionally long (z300-400 ps) uorescence lifetime. The selection of the mixed dinucleotide d(ApG) for investigation was further motivated by the observed large effects on the uorescence lifetimes upon substitution of an increasing number of adenines in a d(A) 20 strand by guanines.…”

“…Experimental section), the extra phosphate of d(pApG) compared to d(ApG) does not alter the relevant dual fluorescence properties of the dinucleotide. 1,[40][41][42][43][44][45][46]…”

Intrinsic fluorescence of B and Z forms of poly d(G-m5C)·poly d(G-m5C), a synthetic double-stranded DNA: spectra and lifetimes by the maximum entropy method

“…Because of these difficulties and the compositional complexity of naturallyoccurring DNAs recent work has focused on various dinucleoside phosphates (DNPs) and synthetic DNAs. [6][7][8][9][10][11] From this work it has emerged that the emissions are multi-component, comprising a fast-decaying, polarized band attributable to monomer fluorescences and two others at longer wavelengths, depolarized and with nanosecond lifetimes, attributable to emissions from stacked, excimer-like states. The existence of two excimer-like emissions was puzzling and though correlations existed with an extensive study of several DNPs showing the coexistence of right-handed and left-handed stacking of the bases, 8,11 direct evidence for an assignment of the emissions to these conformers was missing.…”